ADM Roadway Design Manual

ROADWAY DESIGN MANUAL – Roads and Bridges

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PART 1: ROADWAY DEVELOPMENT SECTION 100: GENERAL INFORMATION 101 PURPOSE 101.01 INTRODUCTION 102 CONTENTS AND ORGANIZATION 102.01 PART 1: ROADWAY DEVELOPMENT 102.02 PART 2: ROADWAY DESIGN 102.03 PART 3: STRUCTURES AND BRIDGES 103 TECHNICAL MEMORANDUMS 103.01 GENERAL 103.02 TECHNICAL MEMORANDUMS - GENERAL 103.03 TECHNICAL MEMORANDUMS - SPECIFIC 104 ROADWAY CLASSIFICATIONS 104.01 ROADWAY SYSTEM 104.02 DESIGN 104.03 CRITERIA FOR DESIGN CLASS DESIGNATION 105 ROUTE DESIGNATIONS 105.01 INTRODUCTION 105.02 ROUTE NUMBERS 105.03 ADDITIONS, DELETIONS, AND REVISIONS

100-1 100-1 100-1 100-1 100-2 100-2 100-2 100-2 100-2 100-3 100-3 100-3 100-3 100-3 100-5 100-5 100-5 100-5

SECTION 200: DESIGN CONCEPT DEVELOPMENT 201 TRANSPORTATION PLANNING 201.01 INTRODUCTION 201.02 ROAD SECTION 201.03 TOWN PLANNING 201.04 MAPPING 201.04.01 General 201.04.02 Topographic Mapping 201.05 PROJECT LIMITS 201.06 PROJECT IDENTIFICATION AND NUMBERING 201.07 INTERDEPARTMENTAL COORDINATION 202 ENVIRONMENTAL FACTORS INFLUENCING DESIGN 202.01 INTRODUCTION 202.02 SOCIOECONOMIC/COMMUNITY RESOURCE DATA 202.02.01 Land Use 202.02.02 Growth Projections 202.02.03 Public Services 202.02.04 Schools 202.02.05 Mosques 202.02.06 Utilities 202.02.07 Security 202.02.08 Commercial Activities 202.02.09 Economics 202.02.10 Local Transportation/Circulation 202.02.11 Parking Requirements 202.02.12 Recreation 202.02.13 Historical Site Identification and Preservation 202.03 NATURAL/ENVIRONMENTAL RESOURCE DATA 202.03.01 Landscape Preservation 202.03.02 Topography 202.03.03 Water 202.03.04 Wildlife 202.03.05 Air Quality 202.03.06 Noise

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202.03.07 Visual/Aesthetic 202.03.08 Hazardous Materials 202.04 ENVIRONMENTAL CHECKLIST 203 TECHNICAL INVESTIGATIONS 203.01 INTRODUCTION 203.02 GEOTECHNICAL ENGINEERING 203.03 TRAFFIC COUNTS 203.03.01 Introduction 203.03.02 Traffic Projections 203.03.03 Procedures for Traffic Volumes 203.04 SURVEY CONTROL/FIELD SURVEYS 203.04.01 Introduction 203.04.02 Horizontal Control 203.04.03 Vertical Control 203.04.04 Coordinate System 203.04.05 Field Surveys 203.5 DRAINAGE SURVEYS

200-11 200-11 200-12 200-12 200-12 200-12 200-12 200-12 200-13 200-14 200-14 200-14 200-14 200-14 200-14 200-14 200-15

SECTION 300: DESIGN CONCEPT REPORT 301 CONTENTS 301.01 FORMAT 302 EXECUTIVE SUMMARY 303 INTRODUCTION 304 TRAFFIC ANALYSIS 305 DESCRIPTION OF ALTERNATIVES 306 DESIGN DATA 307 TYPICAL SECTIONS 308 GEOMETRICS 309 INTERCHANGE/ INTERSECTION CONFIGURATION 310 PARKING STUDY 311 HYDROLOGY AND HYDRAULICS 311.01 PURPOSE 311.02 PLANNING & PREPARATION OF THE DRAINAGE DESIGN CONCEPTS 311.02.01 Problem Categories 311.02.02 Flood Plain Encroachment and Risk Evaluation 311.02.03 Data Collection 311.03 STORM WATER HYDROLOGY 311.04 OPEN CHANNEL HYDRAULICS 311.05 BRIDGE HYDRAULICS 311.05.01 Bridge Location and Hydraulics Report 311.05.02 Bridge Hydraulics Recommendations Sheet (BHRS) 311.06 STORMWATER MANAGEMENT USING RETENTION/DETENTION DESIGN 312 SUBSURFACE INVESTIGATIONS 313 BRIDGE TYPE SELECTION 313.01 BRIDGES OVER WATERWAYS 313.02 WIDENINGS/REHABILITATION 313.03 BRIDGE SELECTION REPORT 314 UTILITY IMPACT ANALYSIS 315 SOCIOECONOMIC ANALYSIS 316 AGRICULTURE IMPACT 317 PUBLIC FEEDBACK 318 SIGNING AND PAVEMENT MARKINGS 319 LIGHTING CONCEPTS 320 CONSTRUCTION STAGING 321 COST ESTIMATE 322 CONCLUSIONS/RECOMMENDATIONS

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323 APPENDIX 324 DRAWINGS

300-25 300-25

PART 2: ROADWAY DESIGN SECTION 100: GENERAL DESIGN CRITERIA 101 DESIGN SPEED 102 DESIGN VEHICLES 103 DESIGN TRAFFIC 103.01 DESIGN PERIOD 103.02 RELATION TO DESIGN 104 ROADWAY CAPACITY 104.01 DESIGN CAPACITIES 104.01.01 Multi-lane Rural Roadway 104.01.02 Two Lane Roadways 104.01.03 Expressways 104.01.04 Expressway Ramps and Weaving Sections 104.01.05 Intersection Capacity 105 CONTROL OF ACCESS 105.01 GENERAL 105.02 ACCESS CONTROL DESIGN CRITERIA 105.02.01 Primary Roadways 105.02.02 Secondary Roadways, ADT > 2500 105.02.03 Secondary Roadways, ADT < 2500 105.03 USE OF FRONTAGE ROADS 105.04 PROTECTION OF ACCESS RIGHTS 106 DESIGN STANDARD EXCEPTIONS 107 BICYCLE FACILITIES 107.01 GENERAL 107.02 SPECIAL BICYCLE FACILITIES 107.03 BICYCLE CHARACTERISTICS 107.04 BICYCLES AT INTERSECTIONS

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SECTION 200: GEOMETRIC DESIGN STANDARDS 201 SIGHT DISTANCE 201.01 GENERAL 201.02 PASSING SIGHT DISTANCE 201.03 STOPPING SIGHT DISTANCE 201.04 STOPPING SIGHT DISTANCE AT GRADE CRESTS 201.05 STOPPING SIGHT DISTANCE AT GRADE SAGS 201.06 STOPPING SIGHT DISTANCE ON HORIZONTAL CURVES 201.07 DECISION SIGHT DISTANCE 202 SUPERELEVATION 202.01 GENERAL 202.02 SUPERELEVATION STANDARDS 202.03 CITY ROAD CONDITIONS 202.04 AXIS OF ROTATION 202.05 SUPERELEVATION TRANSITION 202.06 SUPERELEVATION OF COMPOUND CURVES 203 HORIZONTAL ALIGNMENT 203.01 GENERAL 203.02 STANDARDS FOR HORIZONTAL CURVATURE 204 VERTICAL ALIGNMENT 204.01 GENERAL 204.02 VERTICAL ALIGNMENT POSITION WITH RESPECT TO CROSS SECTION 204.03 STANDARDS FOR GRADES

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204.04 VERTICAL CURVES 204.05 LONG SUSTAINED GRADES 204.06 STRUCTURE GRADE LINE 204.07 SEPARATE PROFILE GRADE LINES 205 COORDINATION OF HORIZONTAL AND VERTICAL ALIGNMENTS 206 PAVEMENT TRANSITIONS 206.01 GENERAL 206.02 TRANSITIONS FOR MULTILANE ROADWAYS 207 BRIDGES AND GRADE SEPARATION STRUCTURES 207.01 CLEAR WIDTH 207.02 CROSS SLOPE 207.03 SIDEWALKS 208 PEDESTRIAN FACILITIES 208.01 SIDEWALKS 208.02 PEDESTRIAN GRADE SEPARATIONS 208.03 PEDESTRIAN UNDERPASSES 209 CURBS 209.01 GENERAL 209.02 TYPES AND USES 209.03 CURB PARAMETERS 210 BUS STOPS AND TAXI STOPS 210.01 BUS STOPS 210.02 TAXI STOPS 211 PARKING 211.01 GENERAL 211.02 PARKING AREAS 211.03 ON ROAD PARKING SPACES 211.04 PARKING LOTS 211.05 PARKING DEMAND/SUPPLY ANALYSIS

200-11 200-11 200-11 200-16 200-16 200-16 200-16 200-16 200-18 200-18 200-18 200-18 200-18 200-18 200-18 200-18 200-18 200-18 200-19 200-19 200-19 200-19 200-19 200-20 200-20 200-20 200-20 200-21 200-21

SECTION 300: GEOMETRIC CROSSECTIONS 301 TRAVELLED WAY STANDARDS 301.01 TRAVELLED WAY WIDTH 301.02 TRAVELLED WAY CROSS SLOPES 302 SHOULDER STANDARDS 302.01 SHOULDER WIDTH STANDARDS 302.02 SHOULDER CROSS SLOPES 303 SIDE SLOPE STANDARDS 303.01 SIDE SLOPE VALUES 303.02 SLOPE CLEARANCE FROM RIGHT OF WAY 304 MEDIAN STANDARDS 305 CROSS SECTION ELEMENTS 305.01 RURAL FREEWAY/EXPRESSWAY CROSS SECTION 305.02 URBAN FREEWAY/EXPRESSWAY CROSS SECTION 305.03 ARTERIAL (MAIN ROAD) CROSS SECTION 305.04 SECTOR ROAD CROSS SECTION 305.05 FRONTAGE ROAD CROSS SECTION 306 HORIZONTAL AND VERTICAL CLEARANCES 306.01 HORIZONTAL CLEARANCES 306.02 VERTICAL CLEARANCES 306.03 TUNNEL CLEARANCES 307 CLEAR ZONE CONCEPT 307.01 APPLICATION OF CLEAR ZONE 307.01.01 Roadside Terrain: Foreslope 307.01.02 Roadside Terrain: Backslope 307.01.03 Roadside Terrain: Cross-slope

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307.01.04 Roadside Terrain: Ditch 308 BARRIERS 308.01 BARRIER NEED 308.02 ROADSIDE BARRIER TYPES AND FEATURES 308.03 ROADSIDE BARRIER PLACEMENT 308.03.01 Lateral Placement 308.03.02 Barrier to Hazard Clearances 308.03.03 Effects of Roadside Terrain 308.03.04 Barrier Length Design 308.04 MEDIAN BARRIERS 308.04.01 Median Barrier Warrants 308.04.02 Median Barrier Types and Features 308.05 MEDIAN BARRIER PLACEMENT 308.05.01 Median Geometry 308.05.02 Treatment of Fixed Object Hazards 308.06 END TREATMENTS AND CRASH CUSHIONS 308.06.01 End Treatments 308.06.02 Crash Cushion-Selection Guidelines 308.06.03 Placement Recommendations

300-9 300-11 300-11 300-11 300-12 300-12 300-12 300-13 300-13 300-15 300-15 300-15 300-15 300-15 300-16 300-16 300-16 300-18 300-18

SECTION 400: AT-GRADE INTERSECTIONS 401 GENERAL 402 DESIGN CONSIDERATIONS 403 AT GRADE INTERSECTION TYPES 404 CHANNELIZATION 404.01 PREFERENCE TO MAJOR MOVEMENTS 404.02 AREAS OF CONFLICT 404.03 INTERSECTION ANGLES 404.04 POINTS OF CONFLICT 404.05 SPEED-CHANGE LANES 404.06 TURNING MOVEMENTS 404.07 REFUGE AREAS 404.08 PROHIBITED TURNS 404.09 EFFECTIVE SIGNAL CONTROL 404.10 INSTALLATION OF TRAFFIC CONTROL DEVICES 404.11 GUIDELINES 405 DESIGN VEHICLES 405.01 OFF TRACKING 405.02 DESIGN VEHICLES 405.03 TURNING TEMPLATES 406 INTERSECTION DESIGN STANDARDS 406.01 SIGHT DISTANCE 406.02 EFFECT OF SKEW 406.03 EFFECT OF VERTICAL PROFILES 406.04 LEFT-TURN CHANNELIZATION 406.05 RIGHT-TURN CHANNELIZATION 406.06 TRAFFIC ISLANDS 407 ROUNDABOUT DESIGN

400-1 400-1 400-1 400-2 400-2 400-2 400-2 400-2 400-3 400-3 400-3 400-3 400-3 400-3 400-3 400-4 400-4 400-4 400-4 400-4 400-4 400-10 400-13 400-13 400-14 400-14 400-15

SECTION 500: INTERCHANGES 501 GENERAL 502 INTERCHANGE WARRANTS 503 DESIGN CONSIDERATIONS 504 INTERCHANGE TYPES 504.01 THREE-LEG INTERCHANGE 504.02 FOUR-LEG INTERCHANGES

500-1 500-1 500-1 500-1 500-1 500-3

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505 INTERCHANGE DESIGN PROCEDURES 506 INTERCHANGE DESIGN STANDARDS 507 RAMP DESIGN STANDARDS 508 ENTRANCE/ EXIT RAMP DESIGN STANDARDS 508.01 RAMP TERMINAL DESIGN

500-8 500-8 500-9 500-11 500-16

SECTION 600: GEOTECHNICAL ENGINEERING 601 INTRODUCTION 602 GENERAL 603 GEOTECHNICAL REPORT 604 STRUCTURAL PAVEMENT SECTION DESIGN 604.01 GENERAL 604.01.01 Pavement Design Methods 604.01.02 Comparison of Design Results 604.02 PAVEMENT DESIGN METHOD

600-1 600-1 600-1 600-2 600-2 600-2 600-4 600-5

SECTION 700: DRAINAGE 701 GENERAL

700-1

SECTION 800: UTILITIES 801 GENERAL 802 UTILITY PLANNING 803 SERVICE RESERVATIONS 804 UTILITY DESIGN 804.01 GENERAL 804.02 UTILITY PROTECTION 804.03 UTILITY RELOCATION 804.04 CONTINGENCY DUCTS 804.05 UTILITY LOCATIONS 804.06 NON-DISRUPTIVE ROAD CROSSINGS

800-1 800-1 800-2 800-3 800-3 800-3 800-4 800-4 800-4 800-4

SECTION 900: TRAFFIC ENGINEERING 901 TRAFFIC OPERATIONAL ANALYSIS 901.01 GENERAL 901.02 OPERATIONAL ANALYSIS 902 SIGNALIZATION 902.01 TRAFFIC SIGNAL DESIGN 902.02 SIGNALS, POLES, AND CONTROLLERS 902.03 DUCTS AND PULLBOXES 902.04 PYLONS 903 TRAFFIC SURVEILLANCE 904 SIGNING 904.01 SIGN STRUCTURE INSTALLATIONS 904.01.01 Ground Mounted 904.01.02 Overhead Mounted 904.02 SIGN SHEETING 904.03 SIGN TYPES 904.03.01 Regulatory And Warning Signs 904.03.02 Guide Signs 904.04 FINAL SIGNING PLAN REQUIREMENTS 904.05 ARABIC LETTERING FOR GUIDE SIGNS 904.05.01 General 904.05.02 The Arabic Alphabet 904.05.03 Use of the Standard Arabic Script 904.06 GUIDE SIGN DIMENSIONS

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904.06.01 Single Message Guide Signs (Example 900-02) 904.06.02 Multiple Message Guide Signs (Example 900-03) 904.07 STANDARD ARABIC SCRIPT FOR HIGHWAY SIGNS 1 OF 14 904.08 SIGN LIGHTING 904.09 SIGN LUMINARES 905 PAVEMENT MARKINGS 905.01 GENERAL 905.02 TYPES OF PAVEMENT MARKINGS 905.02.01 Lane Markings 905.02.02 Stop Line Markings 905.02.03 Pedestrian Crossing Markings 905.02.04 Channelization Markings 905.02.05 Pavement Edge Markings 905.02.06 Parking Space Markings 905.02.07 Pavement Symbols 906 MAINTENANCE OF TRAFFIC 906.01 CONSTRUCTION STAGING 906.02 SAFETY MEASURES 906.03 TEMPORARY TRAFFIC SIGNALS 906.04 MAINTENANCE OF TRAFFIC PLANS

900-10 900-12 900-15 900-29 900-29 900-29 900-29 900-29 900-29 900-30 900-30 900-30 900-30 900-30 900-30 900-30 900-30 900-31 900-31 900-31

SECTION 1000: LIGHTING 1001 ROADWAY LIGHTING 1001.01 GENERAL 1001.02 LIGHTING DESIGN CONSIDERATIONS 1001.03 ILLUMINATION REQUIREMENTS 1002 PARKING AREA LIGHTING 1002.01 GENERAL 1002.02 ILLUMINATION REQUIREMENTS 1002.03 LANTERN MOUNTING HEIGHT 1002.04 LANTERN SELECTION 1003 SIDEWALK LIGHTING 1003.01 GENERAL 1003.02 ILLUMINATION REQUIREMENTS 1003.03 LANTERN MOUNTING HEIGHT 1003.04 LANTERN SELECTION 1004 LIGHTING CONTROLS 1004.01 GENERAL 1004.02 LIGHTING CONTROLLER REQUIREMENTS 1004.03 DESIGN STANDARDS AND PROCEDURES 1005 POWER DISTRIBUTION 1006 DESIGN AND SUPERVISION RESPONSIBILITIES

1000-1 1000-1 1000-1 1000-2 1000-3 1000-3 1000-3 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-4 1000-5

SECTION 1100: ROADSIDE DEVELOPMENT 1101 LANDSCAPING 1102 IRRIGATION 1102.01 IRRIGATION DUCTS 1103 FENCING 1104 SLOPE PAVING 1105 SWEET SAND COVERING 1106 STREET FURNITURE 1106.01 GENERAL 1106.02 DESIGN 1106.03 BENCHES 1106.03.01 Type A bench 1106.03.02 Type B bench

1100-1 1100-1 1100-1 1100-2 1100-2 1100-2 1100-2 1100-2 1100-2 1100-2 1100-2 1100-2

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1106.03.03 Type C bench 1106.04 BUS SHELTERS 1106.05 TELEPHONE BOOTHS 1107 NOISE ABATEMENT

1100-3 1100-3 1100-3 1100-3

PART 3: STRUCTURE DESIGN SECTION 100: DESIGN CRITERIA 101 GENERAL 101.01 PURPOSE 101.02 DEFINITIONS 101.03 BRIDGE TYPES 102 DESIGN FEATURES 102.01 GENERAL 102.02 DESIGN METHODS 102.03 VERTICAL CLEARANCE AT STRUCTURES 102.03.01 Highway Traffic Structures 102.03.02 Pedestrian Overpasses 102.03.03 Railroad Overpasses 102.03.04 Tunnels 102.03.05 Sign Structures 102.03.06 Width 102.04 RAILINGS 102.05 CONCRETE BARRIER TRANSITIONS 102.06 APPROACH SLABS 102.07 ANCHOR SLABS 102.08 DECK DRAINAGE 102.09 WING WALLS 102.10 LIGHTING 102.11 BRIDGE DECK ELEVATIONS 102.12 CONCRETE CRACK CONTROL 102.13 CORROSION PROTECTION 103 ARCHITECTURAL CONSIDERATIONS 103.01 PROCEDURE 103.02 GENERAL CRITERIA

100-1 100-1 100-1 100-1 100-2 100-2 100-2 100-2 100-2 100-2 100-2 100-3 100-3 100-3 100-3 100-3 100-3 100-3 100-3 100-4 100-4 100-4 100-4 100-4 100-4 100-4 100-5

SECTION 200: DESIGN LOADS 201 LOAD TYPES 201.01 GENERAL 201.02 DEAD LOADS 201.03 FUTURE WEARING SURFACE 201.04 WEARING SURFACE 201.05 HIGHWAY LOADS 201.06 STRUCTURE LOADINGS 201.07 FRICTION FORCES 201.08 THERMAL FORCES 201.09 STREAM FORCES 201.10 LATERAL EARTH PRESSURE 201.11 DIFFERENTIAL SETTLEMENT 201.12 EARTHQUAKES 202 DISTRIBUTION OF LOADS 202.01 SUPERIMPOSED DEADLOAD DISTRIBUTION 202.02 CONCRETE BOX GIRDERS 202.03 PRESTRESSED VOIDED SLABS 202.04 PRESTRESSED BOX BEAMS 202.05 LATERAL TENSIONING OF MULTI-BEAM UNITS

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202.06 LIVE LOAD DISTRIBUTION 203 LOAD FACTORS

200-5 200-5

SECTION 300: REINFORCED CONCRETE 301 GENERAL 301.01 CONCRETE 301.02 DIAPHRAGMS 301.03 DESIGN METHODS 301.04 REINFORCEMENT 302 SLAB DESIGN 302.01 SPAN LENGTHS 302.02 SLAB THICKNESS 302.03 PROTECTION AGAINST CORROSION 302.04 DISTRIBUTION METHOD 302.05 RAILING LOADS

300-1 300-1 300-1 300-1 300-1 300-1 300-2 300-2 300-2 300-2 300-2

SECTION 400: PRESTRESSED CONCRETE 401 DESIGN CRITERIA 401.01 GENERAL 401.02 ALLOWABLE STRESSES—CONCRETE 401.03 SHEAR 402 POST TENSIONED BOX GIRDER BRIDGES 402.01 GENERAL 402.02 CONCRETE 402.03 BEARING PADS 402.04 CREEP AND SHRINKAGE 402.05 FLANGE AND WEB THICKNESS - BOX GIRDERS 402.06 DIAPHRAGMS 402.07 DEFLECTIONS 402.08 ALLOWABLE STRESSES - PRESTRESSING STEEL 402.09 ALLOWABLE STRESSES-CONCRETE 402.10 LOSS OF PRESTRESS 402.11 FLEXURAL STRENGTH 402.12 SHEAR 402.13 FLANGE REINFORCEMENT 402.14 METHOD OF ANALYSIS 403 PRECAST PRESTRESSED CONCRETE 403.01 CONCRETE 403.02 DEFLECTIONS 403.03 ALLOWABLE STRESSES-PRESTRESSING STEEL 403.04 ALLOWABLE STRESSES-CONCRETE 403.05 LOSS OF PRESTRESS 403.06 SHEAR 403.07 METHOD OF ANALYSIS 404 PRESTRESSED I-GIRDERS 404.01 GENERAL 404.02 CONCRETE 404.03 EFFECTIVE FLANGE WIDTH 404.04 SHEAR 404.05 INTERMEDIATE DIAPHRAGMS 404.06 BEARING PADS 404.07 CREEP FACTOR 404.08 FRAMES AND CONTINUOUS CONSTRUCTION 404.09 DIFFERENTIAL SHRINKAGE 404.10 METHOD OF ANALYSIS 405 PRESTRESSSED VOIDED SLABS

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405.01 END BLOCKS 405.02 DIAPHRAGMS 405.03 LATERAL TIES 405.04 SHEAR KEYS 405.05 BARRIERS 406 PRESTRESSED BOX BEAMS 406.01 END BLOCKS 406.02 DIAPHRAGM 406.03 LATERAL TIES 406.04 SHEAR KEYS

400-7 400-7 400-7 400-7 400-7 400-7 400-7 400-7 400-7 400-7

SECTION 500: STRUCTURAL STEEL 501 DESIGN CRITERIA 501.01 GENERAL 501.02 DESIGN METHODS 501.03 MATERIALS 501.04 ALLOWABLE FATIGUE STRESS 501.05 LOAD CYCLES 501.06 CHARPY V-NOTCH IMPACT REQUIREMENTS

500-1 500-1 500-1 500-1 500-1 500-1 500-1

SECTION 600: EXPANSION AND CONTRACTION 601 MOVEMENT CRITERIA 601.01 MOVEMENT RATING 602 DECK JOINTS 602.01 GENERAL 602.02 COMPRESSION SEALS 602.03 STRIP SEALS 602.04 MODULAR JOINTS 603 BEARINGS 603.01 GENERAL 603.02 NEOPRENE STRIPS 603.03 ELASTOMERIC BEARING PADS 603.04 STEEL BEARINGS 603.05 SLIDING ELASTOMERIC BEARINGS 603.06 HIGH-LOAD MULTI-ROTATIONAL BEARINGS 603.06.01 Description 603.06.02 Rotational Requirements 603.06.03 Use 603.06.04 Design Criteria 603.07 BEARING SCHEDULE 604 RESTRAINING DEVICES 604.01 GENERAL 604.02 VERTICAL FIXED RESTRAINERS 604.03 VERTICAL EXPANSION RESTRAINERS 604.04 EXTERNAL SHEAR KEYS 604.05 INTERNAL SHEAR KEYS 604.06 KEYED HINGE

600-1 600-1 600-1 600-1 600-2 600-2 600-2 600-2 600-2 600-3 600-3 600-4 600-4 600-4 600-4 600-5 600-5 600-5 600-7 600-7 600-7 600-7 600-8 600-8 600-8 600-8

SECTION 700: GEOTECHNICAL 701 FOUNDATIONS 701.01 GENERAL 701.02 SPREAD FOOTINGS 701.03 PILE FOUNDATIONS 701.04 DRIVEN PILES 701.05 BORED PILES

700-1 700-1 700-1 700-1 700-2 700-2

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SECTION 800: RETAINING WALLS 801 DESIGN CRITERIA 801.01 GENERAL 801.02 POLICY 801.03 RESPONSIBILITIES 801.03.01 Roadway Design Section 801.03.02 Geotechnical Section 801.03.03 Bridge Design Section 801.04 PROPRIETARY RETAINING WALLS

800-1 800-1 800-1 800-1 800-1 800-2 800-2 800-2

SECTION 900: MISCELLANEOUS 901 TRAFFIC STRUCTURAL SUPPORTS 901.01 GENERAL 901.02 WIND SPEED 901.03 ALLOWABLE STRESSES 902 UTILITIES IN STRUCTURES 902.01 GENERAL 902.02 POLICY 902.03 UTILITY AGENCY RESPONSIBILITY 902.04 BRIDGE GROUP RESPONSIBILITY 903 FALSEWORK POLICY FOR BRIDGE CONSTRUCTION 903.01 FALSEWORK REQUIREMENTS 903.02 FALSEWORK USE 903.03 FALSEWORK CLEARANCES 904 CONSTRUCTION JOINT GUIDELINES FOR BRIDGE CONSTRUCTION 904.01 GENERAL 904.02 LONGITUDINAL CONSTRUCTION JOINTS 904.03 PRECAST CONCRETE GIRDER BRIDGES 904.04 STEEL GIRDER BRIDGES 904.05 CAST-IN-PLACE BOX GIRDER BRIDGES

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PART 1 ROADWAY DEVELOPMENT

complete. The companion documents to this manual are: z

SECTION 100 GENERAL INFORMATION

z z z

101 101.01

PURPOSE

Standard Specifications for Roads and Bridge Construction - 1996 Consultant Procedures Manual - 1997 Roadway Standard Drawings - 1996 Construction Supervision Manual - 1997

Where the Consultant's scope of work and this manual conflict, the scope of work shall govern.

INTRODUCTION

The Manual is intended to serve as a guide for the design of the roads and highways that fall under the jurisdiction of the Road Section, Abu Dhabi Municipality. The Manual provides a range of acceptable values for critical dimensions and outlines parameters that will help designers conform to the expectations of the Road Section of the Abu Dhabi Municipality. It is assumed that the user has the educational and engineering experience necessary to properly implement its procedures, guidelines and criteria.

Revisions and additions to this manual will be issued from time to time as required. This section contains information regarding technical memorandums used to submit future revisions and additions.

It is perceived that this manual will promote the following:

102

1. All designs will be based on identical criteria. 2. Plans will have a consistent, well-organized format which will not vary greatly from project to project. 3. Familiarization of criteria and procedures will be simplified. 4. The technical review process will be expedited for both the Road Section and the Consultant. 5. Cost efficiencies will be realized during design by an early understanding of procedures and criteria to be employed.

Further contained in this section is an overview of the layout of the manual content, roadway classifications, route designations connecting U.A.E cities and emirates, and streets and place names as assigned by Abu Dhabi Municipality.

CONTENTS AND ORGANIZATION

The scope of the Roadway Design Manual is comprehensive, and is divided into three parts. The three parts are further divided into sections, each with appropriate sub-sections. The three parts are: Part 1 Roadway Development Part 2 Roadway Design Part 3 Structures and Bridges 102.01

PART 1: ROADWAY DEVELOPMENT

The manual is presented in loose-leaf form to facilitate revisions and additions. This manual utilized established analysis techniques and design standards from recognized technical associations that are listed as references in Appendix A.

The purpose of the Roadway Development part is to outline the information and data which must be analyzed to determine a project’s scope. This information and analyses are assembled into a Design Concept Report, which becomes the basis for the project design.

When the Roadway Design Manual is combined with the four companion documents listed below, the standardization of the planning, design and construction of roadway projects will be

The Roadway Development part is divided into three sections. The first section explains the formal organization of this manual and the other two sections, the Design Concept Development

Part 1 100-1

ROADWAY DESIGN MANUAL – Roads and Bridges and the Design Concept Reports, define the conceptual design of the project. The Design Concept Section includes subsections in Transportation Planning, Socio-economic Data, and Technical Investigations. Conceptual Design must be based upon site specific community considerations that reflect military, utility, environmental features, physical properties of the site, and circulation that define the project design. To support the land’s intended use, procurement of the information from departments within the Municipality and outside of Municipality’s organization is required. All the Project-specific data collected forms the basis for the Design Concept Report, a summary of the technical analyses and schematic design that are to be used for plan preparation and construction. 102.02

PART 2:

ROADWAY DESIGN

The purpose of the Roadway Design part is to identify the design standards that all roadway projects are required to meet. The project design is based on these standards. When used in conjunction with the Standard Specifications for Road and Bridge Construction, and Abu Dhabi Roadway Standard Drawings, the resulting project plans and specifications for all projects are completed to the same requirements and format. Specifically, the Roadway Design Part provides details in geometric design standards for each component of the roadway project. The information is divided into eleven sections that include General Design Criteria, Geometric Standards, Geometric Cross Sections, At Grade Intersections, Interchanges, Geotechnical Engineering, Drainage, Utilities, Traffic Engineering, Lighting, and Roadside Development. 102.03

PART 3: STRUCTURES BRIDGES

AND

The purpose of the Structures and Bridges part is to identify the design details with which all structures are required to comply. As with the

Roadway Design part, this document is intended to be used in conjunction with the Standard Specifications and the Abu Dhabi Standard Drawings for the standardization of details for structures and bridges. Uniform design and construction of structures and bridges promotes efficiency of design, construction, and maintenance. This part focuses on features incorporating sound design and costeffective design practices to meet this goal. This part consists of nine sections that cover the general aspects of structures and bridge design. Subjects covered include, General Design Criteria, Design Loads, Reinforced Concrete, Prestressed Concrete, Structural Steel, Expansions and Contractions, Geotech and Retaining Walls. The last section addresses miscellaneous items such as Traffic Supports, Utilities and the Falsework Policy and Requirements.

103 103.01

TECHNICAL MEMORANDUMS GENERAL

This manual will be supplemented from time to time with technical memorandums (TM) addressed to the Consultants for the purpose of transmitting and formalizing appropriate revisions or additions, to the manual. This manual can only be revised by the issuance of a TM authorized and signed by the Chief of Road Section, Abu Dhabi Municipality or his designated representative. Technical memorandums will be developed and issued as two distinct types, general and specific, and are further defined below. 103.02

TECHNICAL MEMORANDUMS - GENERAL

Technical Memorandums - General, deal with issues or information that must be distributed on a system wide basis to all consultants. They are also used to provide advance directives with respect to imminent revision or additions to the Roadway Design Manual. Examples are revisions or refinements to policies, guidelines or criteria.

Part 1 100-2

ROADWAY DESIGN MANUAL – Roads and Bridges 103.03

TECHNICAL MEMORANDUMS - SPECIFIC

Technical Memorandums - Specific, deal with issues or information that is of specific interest to a particular section (design contract), and as such have no influence or effect on other design sections.

The design classes discussed in this section are applicable to all highway networks in both rural and urban areas under the jurisdiction of the Road Section, Abu Dhabi Municipality. Table 100.01 summarizes the major characteristics of the first tier classifications, i.e., primary, secondary and local roads. Table 100.02 is a matrix that differentiates the urban and rural roadway types by their first tier classifications. 104.02

DESIGN

Roadway design standards are dependent on the classification of the roadway. The Road Section will determine the classification. The Design Concept Report summarizes the design criteria to be utilized in the design.

Examples of such memorandums are: 1. 2. 3. 4.

Deviations from the Design Procedures Manual on a project specific basis. Drainage Design Guidelines. Lighting Design Guidelines. Report Transmittals, etc.

104

ROADWAY CLASSIFICATIONS

104.01

ROADWAY SYSTEM

The roadway classification system is based on a hierarchy of roads. Local roads provide access to adjacent land. Collectors provide a combination of land access and movement of through traffic. Arterials and expressways provide for movement of through traffic. Arterials and Expressways have at-grade or grade-separated intersections. Freeways shall have only grade-separated crossings and interchanges. 104.03

Table 100.03 defines the characteristics of the second-tier classifications, i.e., freeways, expressways, arterials, and collectors as they relate to design requirements.

Roadways within the jurisdiction of Abu Dhabi Municipality are classified into one of three functional categories, consistent with the Transportation Master plan: z

z

z

CRITERIA FOR DESIGN CLASS DESIGNATION

Primary Roads Freeways Expressways Secondary Roads Arterials Collectors Local Roads Part 1 100-3


Table 100.01 Summary of Functional Characteristics for Roadway Classifications*

Primary Roads

Secondary Roads

Local Roads

Function

Regional transportation

Regional transportation and/or service to major land developments

Local circulation

Service Points

Connects multiple regions. Serves international connections and major military installations.

Residential, industrial, and recreational areas not served by higher class.

Population Density

Connections to urban areas of 100,000 or more.

Connects two regions. Serves international connections, military installations and seaports not served by Primary Roads. May connect two Primary Roads. Connections to urban areas of 50,000 or more.

Access

Access is controlled.

May be controlled.

Minimal control.

None

Minimum Level of Service

C/D

C

D

Percent of Total Kilometers

35

35

30

Design Speed

Weather Related Road Closures - Allowable Frequency

120 kph (urban) 140 kph (rural)

60 kph (urban) 60-100 kph (rural)

50 kph (urban) 60-90 kph (rural)

Once per 100 years.

Once per 50 years.

Once per 25 years.

Minimum Percent of Truck Traffic (Other Than Pickups)

25

20

* See Part 2.0 for further details.

Part 1 100-4

30

ROADWAY DESIGN MANUAL – Roads and Bridges 105 105.01

105.02

ROUTE DESIGNATIONS

Figure 100.01 shows the designated route numbers between emirates and cities within the U.A.E.

INTRODUCTION

The purpose of route designations is to provide the highway user with a consistent expectation of the: z

z

z

ROUTE NUMBERS

Figure 100.02 shows routes designated between existing primary roads and secondary or local roads in the Abu Dhabi Emirate.

relative direction (north, south, east west) design standards (design speeds, shoulders, etc. resulting from the highway classification) origin/destination of the road.

105.03

ADDITIONS, DELETIONS, AND REVISIONS

From time to time, it may become necessary to assign new route numbers, delete route numbers for obsolete roads or revise route numbers to reflect changes to road classifications. Users of this manual shall advise the Municipality if they perceive the need for changes to the route numbering system. Note that all changes of this nature are subject to the approval of Abu Dhabi Municipality.

Route designation and numbering facilitate rapid and accurate identification of specific locations in the event of emergencies, accident reporting and analysis and in the inventory of roadway appurtenances, i.e., signs, drainage structures, guardrails, etc. Route assignments are made by the Municipality and based on the functional classification of each roadway.

Table 100.02 Roadway Types by Functional Classification

Roadway Classification Primary

Roadway Type for Design Urban Rural Freeway Expressway

Freeway Expressway

Secondary

Arterial (Main Roads) Frontage Roads

Collector • Major • Minor

Sector Road • Primary • Local

Local Access

Local

Part 1 100-5


Table 100.03 Characteristics of Urban/Rural Design Classes

Freeways/ Expressways

Arterials

Collectors

Locals

Traffic movement primary consideration

Traffic movement and land access of equal importance.

Traffic movement secondary consideration

Land access secondary in consideration

Traffic movement and land access of equal importance.

Land access primary consideration

Uninterrupted except at intersections

Interrupted flow

Interrupted flow

None or limited

Permitted

Permitted

At-grade intersections, interchanges, orslip-ramps At-grade intersections or interchanges

At-grade intersections




Arterials Expressways Freeways Expressways Collectors Freeways

Arterials Expressways

Locals Arterials

Locals

Locals Collectors Expressways

Locals Collectors

Locals Collectors

All types up to 20 percent heavy trucks

All types up to 20 percent heavy trucks All types up to 40% trucks

All types

Passenger & service vehicles

All types, up to 30% heavy trucks in the 3 mg to 5 mg class

Predominantly passenger cars & light to medium trucks: occasional heavy trucks

1,000-12,000 200-4,000

100-1,000 0 to 300

30-50 kph 50-90 kph

30-40 kph 45-80 kph

Traffic Service: Urban and Optimum mobility Rural Land Service: Urban and Rural

Full control of access − no direct land access

Traffic Flow Characteristics: Urban and Free flow Rural Private and Commercial Access: Urban and Not permitted Rural Connection Type for Public Roads: Grade separations & Urban interchanges

Rural

Connects to: Urban

Rural

Vehicle Type: Urban

Rural

Grade separations & interchanges

All types; heavy trucks average 20%-40%

ADT (20): Level of Service is C/D 5,000-30,000 Urban Level of Service is C/D 2,000-15,000 Rural Average Running Speed for Off-Peak Conditions: 80-110 kph 50-80 kph Urban 80-120 kph 60-110 kph Rural Part 1 100-6


Figure 100.01 Route Designations Between U.A.E. Cities and Emirates Part 1 100-7


Figure 100.02 Connections Between Primary and Secondary or Local Roads Part 1 100-8


SECTION 200 DESIGN CONCEPT DEVELOPMENT

Utilities Section - The Town Planning Utilities Section is responsible for the development and approval of all service reservations. 201.04

201

201.01

TRANSPORTATION PLANNING

201.04.01

INTRODUCTION

Data collection comprises this phase of the predesign process. Existing data is collected from the Abu Dhabi Municipality, other government departments, landowners, and field surveys. This data becomes the foundation for project road and bridge design. The Consultant is responsible for all data collection. 201.02

General

Current, accurate base mapping is an essential tool in transportation planning. The specific mapping requirements depend on the length and complexity of the project and its location, either urban or rural. Aerial mapping is normally the most useful and cost-effective medium for larger projects. Ground topographical surveys are used for smaller projects, especially in urban areas and to supplement aerial mapping at specific locations where more detail and accuracy is needed.

ROAD SECTION

The Road Section is the lead department from which all road and bridge projects are initiated and approved. The Consultant shall work with assigned staff to develop the project scope per the Consultant Procedures Manual and identify applicable design criteria from the Roadway Design Manual. The Consultant is expected to develop the project by proper application of Abu Dhabi Municipality policies and standards. 201.03

MAPPING

Three types of aerial maps are used in the planning and design phases of roadway and bridge projects: Uncontrolled Aerial Photography - These maps are produced directly from the aerial photographs that normally cover large areas at a reduced scale. The maps are generally used in route location studies to define transportation corridors and alternative alignments. The contact prints from the aerial photography are assembled to form a photomosaic of the area under study to reduce distortion.

TOWN PLANNING

The Town Planning Department is comprised of two sections: Planning Section - The Planning Section is responsible for the development and maintenance of the Master Plan and planning layouts. The Master Plan is the base document from which the project’s roadway classifications are assigned. Roadway design standards are identified for each roadway classification (see Tables 100.01, 100.02 and 100.03, in Part 1, Section 100, General Information). The planning layouts are used to identify the existing and proposed land use and development intensity.

Controlled Aerial Photography - Prior to the flight, horizontal and vertical ground control points are set and marked in the field. These points are used to control photomosaic products that are significantly more accurate and can be prepared at a specific scale. These maps can be used at larger scales for preliminary engineering activities including Design Concept Reports. Topographic (Aerial) Mapping - These maps represent the state-of-the-art in highway design and consist of topographic maps compiled from controlled aerial photography in a digitized format that can be input directly to CADD. This mapping can be used for both design concept development and final design and is limited to the broad roadway corridor.

Part 1 200-1

ROADWAY DESIGN MANUAL – Roads and Bridges The Consultant is responsible for providing base mapping for design concept development. Specific requirements will be identified in the Consultant’s scope of work. Existing aerial and topographic maps may be available and suitable for use in consultation with the Department. The Abu Dhabi Municipality and Town Planning Department maintain a limited library of existing mapping which the Consultant shall review for background information. Mapping scales and contour intervals generally suitable for the intended purpose are shown in Table 200.01. 201.04.02

Coordinate Grid - Coordinate grid ticks shall be shown on the maps at intervals to suit drawing. North Arrow - A north arrow shall be placed on each map sheet. The north arrow shall be oriented so that north points to the top or to the right of the map sheet. Match lines shall also be labeled so that each sheet may be joined accurately to adjacent sheets. Map Index - A sheet index diagram shall be prepared for each mapping project. This diagram shall show the position and relationship of each sheet to adjacent sheets. A title block is also required and shall be placed on each sheet.

Topographic Mapping

Topographic maps for a specific project shall be prepared in accordance with the following: Survey Control/Field Surveys - The requirements for surveys are included in Section 203.04, Survey Control/Field Survey. CADD Standards - Mapping features and symbology will be prepared in accordance with the latest CADD Standards, supplemented by the standard symbols shown in Figure 200.01, 200.02 and 200.03. Primary Control Points - All primary control points for mapping which were established during the initial field survey will be shown on the maps in their proper locations and with the appropriate symbol, identification number and elevation. A tabulation of the primary control points shall also be shown in the original survey notebook. The tabulation will show the identification number, coordinates and elevation of the point. Supplemental Control Points - All supplemental control points established for controlling aerial photography will be shown on the maps. These include wing points, analytically bridged points, and aerial photo centers. See Figure 200.01. Planimetric Features - Natural and manmade features, spot elevations, topographic features and relevant political subdivision lines shall be plotted on the maps as shown in Figure 200.02 and Figure 200.03.

Table 200.01 Map Scales and Contour Intervals for Highway Development Purpose Scales Interval (m) Route Location Studies: Mountainous 1:5000 Max. 5 Rolling to Flat 1:5000 2 Preliminary Design (DCR): Rural 1:1250 Urban 1:1250

2 2

Rural Design:

1:1250

0.5

Urban Design:

1:500

0.5

Detailed Site Design:

1:100 1:250

0.5 0.5

201.05

PROJECT LIMITS

The Abu Dhabi Municipality will determine the limits of the project. Typically, the limits include the roadway/bridge, medians, sidewalk, parkways, and roadside improvements that enhance the appearance, maintainability and safety characteristics of the project. The project limits may also be determined by phased implementation considerations.

Part 1 200-2


Figure 200.01 Standard Mapping Symbols - Boundaries and Monuments Part 1 200-3


Figure 200.02 Standard Mapping Symbols - Natural Planimetric Features Part 1 200-4


Figure 200.03 Standard Mapping Symbols - Manmade Planimetric Symbols

Part 1 200-5


PROJECT IDENTIFICATION AND NUMBERING

The Abu Dhabi Municipality Road Section will assign the Title and Number for each individual roadway and bridge project. The Consultant will include this information on all drawings, reports, correspondence, calculations and other design documentation associated with the subject project. 201.07

INTERDEPARTMENTAL COORDINATION

Throughout the development of the project, coordination with Municipality Sections as well as other government departments is essential. The Consultant is expected to identify the requirements of the involved government departments, and insure that the project design addresses these requirements. Table 200.02 lists the agency or authority responsible for transportation related functions.

This will contribute significantly to public acceptance and the ultimate success of a project. The following sections describe the various environmental factors that comprise each of the two categories. It is the Consultant’s responsibility to assess each factor and develop a functional and compatible design. 202.02 SOCIOECONOMIC/COMMUNITY RESOURCE DATA The Consultant shall consider each of the following factors as part of the development of project design. The goal is to develop a functional design that accommodates or maintains the integrity of each socioeconomic and community resource with minimal disruption. To assist with the planning involved with the development of the design, the Consultant should map all resources that are capable of being placed onto a map. 202.02.01

Table 200.02 Municipal Agencies Agency/Authority

Function Road/Bridge Construction Planning Utilities Parking Right-of-Way Plantation

202

202.01

ADM-Road Section ADM-Town Planning Dept. ADM-Town Planning Dept. ADM-Road Section ADM-Town Planning Dept. ADM-Agriculture Section

ENVIRONMENTAL FACTORS INFLUENCING DESIGN INTRODUCTION

There are a number of important environmental factors that influence the design of all roadway and bridge projects. These factors are both natural and man-made and have been divided into two major categories; Socioeconomic/ Community Resource Data and Natural/ Environmental Resource Data. The identification of these resources enables the project to be developed to avoid and/or minimize impact to these resources to the greatest extent practicable.

Land Use

The project plans must accommodate existing and future land use to the extent possible. The Consultant is required to provide adequate parking and access to adjacent land uses, commensurate with the type of land use and the roadway classification (see Tables 100.01, 100.02 and 100.03, Part 1, Section 100, General Information). The roadway volumes used to determine the “level of service” (existing and 20year projection) must include the trip generation associated with the adjacent land uses. In the urban areas, the Town Planning Master Plan is the primary document used to identify the types and locations of designated land uses. In rural areas, where the land usage is less defined, the Consultant must conduct a field survey of the existing land uses adjacent to the project. The aforementioned information, combined with the field survey data, will then be used to identify potential improvements to be designed as part of the roadway project. In rural areas, formal information regarding land use may not be available. In these cases, the current land use is typically agricultural and will remain as agricultural unless there is information stating otherwise.

Part 1 200-6

ROADWAY DESIGN MANUAL – Roads and Bridges 202.02.02

Growth Projections

The Abu Dhabi Municipality’s roadways are designed to serve the traffic volume anticipated during the next 20 years. Presently, historical records of past growth trends do not exist. Therefore, it is important that a reasonable growth projection is used to “size” the project. The growth can be categorized as an increase, decrease or no change. It is anticipated that an increase will be the most probable scenario in the foreseeable future. The rate of growth can be expected to increase linearly each year or exponentially (i.e., an order of growth magnitude each year). The growth projection can dramatically affect project “sizing”. Therefore, the Consultant is expected to develop a realistic growth projection which takes into consideration variables such as: • • •

increases in vehicle ownership land use population growth rate, i.e. exponential

linear

or

In the rural areas, information regarding growth is less defined. In these cases, it is necessary that the Consultant make growth projections. These projections should take into account any data concerning growth, including changes in land use adjacent to the roadway. As a starting point, it can be assumed that the use of land is primarily agricultural, with an average growth of 1% to 2% per year for a period of 20 years. The resulting growth projection, along with supporting data and the rationale used to substantiate the project, shall be approved by the Town Planning Section. Public Services

The Consultant is responsible for identifying all public services which may be affected by the roadway/bridge project. In addition, the Consultant is also responsible to compile all relevant design requirements from the affected public services and incorporate these parameters into the project design. It is the Consultant’s responsibility to assure the Abu Dhabi Municipality that the design and construction phasing meets the approval of the affected public service. Table 200.03 identifies the various Public Services and the responsible agency/authority for each.

In urban areas, growth projections are dependent upon the rate at which the Town Planning Master Plan is implemented, as well as the proposed types of land use. The Consultant is expected to confer with the Town Planning Department to ascertain the rate at which the Town Planning Master Plan is to be implemented.

202.02.03

The development of all road and bridge projects typically affects many public services. This can result from encroachment of the improvement project beyond the existing roadway, sidewalk, and bridge. As such, pre-design coordination with public services is required to incorporate design approaches and construction phasing that minimize the project impact.

Table 200.03 Public Services Agency/Authority

Service Road/Bridge Construction Agriculture/Parks Police Fire Security Schools Sanitation Parking Recreational

Navigable Waters Mail Service Public Transportation

202.02.04

ADM-Road Section ADM-Agriculture Police Directorate/ Traffic Police Dept. Civil Defense Dept. Defense Dept./CID Town Planning/ Ministry of Education ADM - Health Section ADM - Road Section Town Planning/ Agriculture Coast Guard Postal Directorate ADM - Public Transport Section

Schools

Schools are an important national resource. The design shall accommodate and preserve sufficient access to all facilities that are affected by project design. Therefore, the Consultant is expected to

Part 1 200-7

ROADWAY DESIGN MANUAL – Roads and Bridges adapt the project’s design to accommodate each school’s needs.

establishment and approval of all Service Reservations.

For each school, there are a number of factors that must be considered in the project design. These include: • school bus traffic • crosswalks • school yard fencing • parking • landscaping • noise attenuation (i.e., insulated windows, soundwalls) • other safety improvement • relocation of affected structures, as necessary • affects on potential school expansion

Table 200.04 lists the Responsible Agencies/Authorities for Utilities. A survey of existing utilities is required. The purpose of the utilities survey is to determine which utilities can: • remain in place based on field surveys, asbuilt plans and other available information: • be protected and/or relocated; and, • affect the horizontal and vertical alignment of the roadway.

In the case of new school site development, the Town Planning Master Plan and Town Planning staff shall be consulted to identify these sites within and/or adjacent to the project limits. As with all other adjacent property improvements, the Consultant is required to provide plans which can be used to construct the necessary improvements either in conjunction with the roadway/bridge project or as a separate project. This is intended so that construction can be undertaken on the school sites during scheduled school closures. 202.02.05

Mosques

Mosques are extremely important to the Islamic faith and cannot be relocated or impacted in any way. The Consultant shall identify all Mosques within close proximity to a proposed project. The project design shall avoid impact to Mosques and shall accommodate and preserve sufficient access to these sites. 202.02.06

Utilities

Major road and bridge projects typically include improvements to all affected utility services. This also includes preparing plans and specifications for these improvements. Pre-design activities require coordination with many agencies/departments. Final design approval of the utility improvements by the utility agencies is also required. The Utilities Section of the Town Planning Department is responsible for

In the case of future or relocated utilities, it may be necessary to preserve adjacent land for utility installation and relocation. The associated costs for utility work shall be identified as part of the design reflected in the project cost estimate for the Design Concept Report. Refer to Part 1, Section 321, Cost Estimate. Table 200.04 Responsible Agency/Authority for Utilities Service Agency/ Authority Water ADM-WED Water (Water and Electricity Dept.) Sewer ADM-Sanitary Drainage Network Section Telephone ETISILAT Electricity ADM-WED Electrical (Water and Electricity Department.) Lighting ADM-WED (Water and Electricity Department) 202.02.07

Security

Nearly every project is affected by some level of security issue. All embassies, government installations, palaces, schools, banks and VIP homes are protected by guards with guardhouses, and associated channeling devices. As a result, many of these facilities interfere with road and bridge projects. The Consultant is required to minimize the relocation of affected facilities as part of the road and bridge project. As with all other adjacent property improvements, the Consultant is required to provide plans which can be used to construct the necessary improvements either in conjunction

Part 1 200-8

ROADWAY DESIGN MANUAL – Roads and Bridges with the roadway/bridge project or as a separate project. This is intended so that construction can be undertaken outside of the project right-of-way at the convenience of the affected property owner. Since each case will vary, the limits of improvement, access, facility relocation, parking, etc. requires review by the affected party and the Abu Dhabi Municipality. The Consultant is also responsible to assure the Department that the proposed improvements located outside of the project right-of-way are agreeable to the affected property owner. 202.02.08

Economics

The Consultant shall assess the economic conditions that exist within the project study area, including income and employment characteristics, tax base and property values. The Consultant shall develop a design that seeks to minimize adverse impacts on these and other economic indicators. This will be done through direct coordination with representatives of the Municipality. 202.02.10

Roadway and bridge projects typically can affect parking. For example, removal of on-street parking to accommodate road widening may result in the need for off-site parking. Each roadway and bridge project requires the preparation of a parking study. The intent of this analysis is to establish existing and ultimate parking requirements.

Local Transportation/Circulation

• • •

• • • •

calculation and survey to establish existing parking demand future growth of parking demand, as a function of land development intensity, vehicle ownership/occupancy trends, etc. opportunity for mixed parking utilization

Both peak and off-peak parking demands should be included in the analysis. Table 200.05 identifies the minimum parking generation rates for Central Business Districts (CBD’s). These rates are to be used in the parking analysis. However, the parking analysis should state the rationale used for proposing rates other than the stated minimum rates. In no case, shall lower parking generation rates be utilized, unless approved by the Abu Dhabi Municipality. In rural areas and for areas outside the CBD, an appropriate parking demand shall be established on the basis of existing development needs, as well as review of the demand for other similar facilities.

In order to insure that the project fully incorporates local transportation/circulation needs, the Consultant shall address the following: •

Parking Requirements

The components of the study include, but are not limited to:

Commercial Activities

The effects of commercial activities on the road and bridge design shall be taken into account. For example, existing access shall be maintained as well as accommodating special features of the non-project site. As a result, coordination with the Town Planning Department, adjacent landowners and governmental departments is required to lessen the impact of the road/bridge improvement project on commercial activities. 202.02.09

202.02.11

Need for Public Transit Stops or Turnouts Staging areas for Regional Transportation Hubs Police Enforcement Pads Pedestrian Walkways and Islands Special Landscape Areas

Part 1 200-9


Use Residential Commercial

202.02.12

Table 200.05 Existing and Future Parking Generation Rates (CBD) Period Rate Vehicle Occupancy Factors Existing 1 space/1000 SF .80 Future 1 space/1000 SF .85 Existing 1 space/500 SF .85 Future 1 space/500 SF .90 Recreation

202.03

A variety of recreation and leisure activities are available to residents of Abu Dhabi. These can include ball fields, beach access, clubs, golf courses, movie theaters and entertainment complexes. As part of the pre-design activities, the Consultant is required to identify the potential effects on adjacent recreational facilities. The Consultant is required to minimize the relocation of affected facilities as part of the road and bridge project. As with all other adjacent property improvements, the Consultant is required to provide plans which can be used to construct the necessary improvements either in conjunction with the roadway/bridge project or as a separate project. 202.02.13

Historical Site Identification and Preservation

The government recognizes the importance of all historical sites and structures that relate to Abu Dhabi’s cultural development. The goal of the government is to identify these sites as they are discovered, and, where appropriate, preserve the sites. During the pre-design process, information regarding historical sites shall be compiled from available sources as well as conducting an initial site survey. The Consultant shall also meet with representatives of the Municipality to determine the significance of the site and present recommendations as to appropriate preservation procedures.

Vehicle Ownership Factors .67 .80 1.00 1.00

NATURAL/ENVIRONMENTAL RESOURCE DATA

Natural/Environmental resources within a project study area shall be assessed and considered during development of the project design. The goal is to develop a functional design that avoids or minimizes impact to the natural environment to the greatest extent practicable. To facilitate the planning process involved in the development of the design, the Consultant should map all resources capable of being placed on a map. 202.03.01

Landscape Preservation

Preservation of existing landscaping, agricultural areas and trees adjacent to proposed roadway projects is extremely important. Pre-design activities include a survey of existing vegetation as part of the design survey stage. The results of this survey are to be discussed with the Abu Dhabi Municipality and the Agriculture Section. Road/bridge improvements including utility locations shall be designed to minimize removal of vegetation. The landscaping survey includes the identification of the number, size, type, condition, and location of all trees, shrubs, succulents, flowers, and grasses. The presence of any vegetation that is specifically protected by decree, or that is considered rare, threatened, or endangered, shall also be identified during the survey. The survey information should then be presented on a scaled plot plan. The scale of each sheet should be adequate to clearly convey the information contained on it. Each sheet should contain a legend, which lists the botanical name of the plant, and its common name. For trees, the size of the tree shall also be listed.

Part 1 200-10

ROADWAY DESIGN MANUAL – Roads and Bridges All urban area projects include landscaping in the medians and other designated areas within the project limits. The landscaping design is normally undertaken by the Agriculture Section. However, the Consultant’s design, shall ensure the following are provided as part of the project, if so required: • • • •

Irrigation Service Sidewalks Walls Fences

The Agriculture Section will assume responsibility for plantings and other special features. Maintenance and operation of the irrigation systems are the responsibility of the Agricultural Section. Topography

Topographic data is important to the development of the Design Concept. Roadway profiles, horizontal alignment, and drainage, are directly affected by topography, which, in turn, affect the project cost. As discussed in Section 201.04, Mapping, the Consultant is expected to review existing maps. In addition, new surveys shall be required to establish the topography for the project. 202.03.03

Water

The Consultant shall identify and determine the importance of all freshwater and saltwater features within the study area. Aquifers and wells, especially those that supply drinking water, shall also be identified within project limits. In developing the design, the Consultant shall avoid impacts to water resources to the greatest extent possible. If avoidance is not an option, the Consultant shall develop a design that minimizes impact to water resources.

Wildlife

The Consultant shall describe any existing wildlife habitat within the project study area. The Consultant is responsible for identifying the types of wildlife species, if any, that are likely to utilize the habitat. The Consultant’s design shall avoid, where possible, those habitat areas that support rare, threatened or endangered wildlife species. 202.03.05

Water for irrigation is reclaimed water from the sewage treatment plant, therefore all large distribution lines require design input from, as well as approval by, the Sanitary Drainage Network Section.

202.03.02

202.03.04

Air Quality

The Consultant shall assess a project’s affect on existing air quality to determine whether or not it will result in significant deterioration due to increased air emissions. 202.03.06

Noise

The Consultant shall assess a proposed project’s affect on ambient noise levels to determine whether or not it will result in a significant deterioration from the existing condition. Noise sensitive receptors, such as Mosques, schools and residential dwellings, shall be identified within the project limits. The Consultant shall strive to develop a design that will have the least increase in noise levels to these receptors. 202.03.07

Visual/Aesthetic

The Consultant shall assess the existing visual and aesthetic appearance of the project study area. In developing the design, the Consultant should consider the effect that the project will have on the visual and aesthetic environment upon build-out. Views from the project of the surrounding environment as well as views of the project from adjacent vantage points shall be considered. The objective of the design is to develop a project that compliments rather than contrasts the existing visual and aesthetic character of the area. 202.03.08

Hazardous Materials

The Consultant shall conduct a survey to identify the actual presence of or likelihood of hazardous material sites within the project study area. Ideally, the project design should be developed to avoid impacting such hazardous sites. This will reduce the health and safety risk and overall

Part 1 200-11

ROADWAY DESIGN MANUAL – Roads and Bridges project cost. If a hazardous materials site cannot be avoided, the Consultant shall take appropriate steps to remediate the hazardous site prior to construction in order to reduce the potential health/safety risk.

• • • •

Geotechnical Traffic Data Collection Survey Control/Field Surveys Drainage Surveys

203.02 202.04

ENVIRONMENTAL CHECKLIST

All of the environmental factors described in Sections 202.02 and 202.03 are included in the Environmental Checklist located at the end of this section. Where appropriate to this project, the Consultant shall use the Environmental Checklist as an initial tool to identify those environmental factors that may influence the design of alternatives The checklist is designed as a question and answer exercise that will aid in the comparison of project alternatives. A response of “No” to a specific question means the environmental factor in question is not applicable to the project. A response of “Yes” or “Maybe” indicates to the Consultant that the environmental resource exists and may be affected by the proposed project. In this case, the resource should be assessed further during the development of alternative designs to determine the exact nature and extent of impact that will be incurred on that resource. The objective is to design a project alternative that has the least amount of adverse impact to the environmental factors on the checklist. An alternative design that yields all “No” answers on the Environmental Checklist is considered to be the ideal design. However, this ideal situation is seldom achieved as there is always some level of impact to the listed environmental considerations.

203 203.01

TECHNICAL INVESTIGATIONS INTRODUCTION

All roadway and bridge projects require technical investigations, to establish the basic building blocks of the design. These technical investigations are initiated in the data collection phase and continue through the development of the Design Concept Report. This subsection identifies the initial activities associated with these investigations. The basic technical investigations include:

GEOTECHNICAL ENGINEERING

The objective of highway geotechnical work should be to seek, interpret, and evaluate subsurface and surface data in order to predict the behavior of the soils and materials along, and adjacent to, the alignment. The resulting information is to be presented in a technical report to be used in the project design. Data collection includes research of existing geotechnical reports which were prepared for other projects in the geographic area as well as field reviews and preliminary testing. For review of existing geotechnical reports, the Abu Dhabi Municipality Road Section as well as other Municipality and Government agencies should be contacted. The existing data will be used to define the number of additional soil borings and the testing requirements for the boring program as described in Part 1, Section 300, Design Concept Report and Part 2, Section 600, Geotechnical Engineering. The Consultant shall obtain approval from the Road Section, Traffic Police and any other concerned agencies prior to commencing geotechnical investigation. 203.03 203.03.01

TRAFFIC COUNTS Introduction

Traffic counts are basic to all phases of highway development and operation. An important component of traffic counts is existing and future traffic volumes. Traffic volumes are needed for highway planning, project cost-benefit comparisons, priority determinations, analyzing, monitoring and controlling traffic movement on the highways, traffic accident surveillance, research purposes, highway maintenance, public information, highway legislation and for many other purposes. However, it should be noted that the traffic data collection and projection techniques described herein are specifically intended for providing traffic volume data required for roadway and bridge design. It is the

Part 1 200-12

ROADWAY DESIGN MANUAL – Roads and Bridges goal of the Abu Dhabi Municipality to establish a permanent automated traffic data collection system for the Municipality. However, until this system is fully developed and implemented, the specific procedures outlined in this section shall be followed in the collection of traffic data for roadway and bridge projects.

next 20 years will increase exponentially. Formula B shall be used when the Engineer judges that the traffic volume will increase linearly.

The procedures which follow establish the minimum requirements; however, this does not preclude the Engineer from using more sophisticated procedures if available.

Where GF = 1 + Annual % Traffic Growth 100

203.03.02

Traffic Projections

The Abu Dhabi Municipality’s roadways are designed to serve the traffic volume anticipated during the next 20 years. Therefore, the existing Average Daily Traffic (ADT) must be projected over a 20-year time frame. For the 20-year travel forecast, variables such as an increase in auto ownership and vehicle registration, population, employment, and residential/ commercial/ industrial land uses which strongly influence the future traffic volume shall be taken into consideration. Presently, a long historical record of past growth trends does not exist. The Abu Dhabi Municipality will use the transportation modeling software for the City of Abu Dhabi. This model shall be the primary source for projected traffic volumes over different time frames. The projected traffic volumes of this transportation modeling software will be based on changes in socioeconomic data for the concerned time period. In case the transportation modeling software is unavailable, then the following formulas shall be used to determine the ADT for a 20-year time frame ADT (20). The Engineer is required to the collect data to determine the current ADT. In addition, the Engineer must provide his rationale for the estimated traffic growth anticipated for the next 20 years by considering all previously acquired data regarding all activity growth in the proximity of the highway improvement.

Formula A: ADT (20) = ADT Present × Growth Factor (GF) 20

Formula B: ADT (20) = ADT present + Annual % Traffic Growth × ADT Present × 20 100 Examples: The following is an example of the use of the two formulas when the annual percent of traffic growth is anticipated to be 10 percent and the ADT at present is 4,000. Formula A: ADT (20) = 4,000 × 1 + 10 100 = (4,000) × (6.73) = 26,920

20

Formula B: ADT (20) = 4,000 + 10 × 4,000 × 20 100 = 4,000 + 8,000 = 12,000 The following is an example of the use of the two formulas when the annual percent of traffic growth is anticipated to be 15 percent over the first 5-year period and 10 percent over the last 15-year period. The ADT present equals 4,000. Formula A: ADT (20) = 4,000 ×

The following formulas may be applied under assumptions of increasing, decreasing, or equal percentages of traffic growth over the 20-year projection. Formula A shall be used when the Engineer judges that the traffic volume over the Part 1 200-13

1 + 15 100

5

+ 1 + 10 100

= 4,000 [(1.15) 5 + (1.10)15] = 4,000 [(2.01) + (4.18)] = 24,760

15

ROADWAY DESIGN MANUAL – Roads and Bridges Formula B: ADT(20) = 4,000+ 15×4,000 ×5 + 10×4000 ×15 100 100 = 4,000 +3,000 + 6,000 = 13,000 203.03.03 Procedures for Traffic Volumes Table 200.06 specifies the minimum procedures that shall be met when traffic studies are conducted to identify the present ADT. Collection of traffic volumes for three functional classes of highways (Primary, Secondary, and Local) and five types of improvements (upgrading existing Primary or Secondary Roads; new Primary or Secondary Road on new alignment/location; upgrading existing intersection/interchange on Primary or Secondary Roads; new intersection/interchange on existing Primary or Secondary Roads; and new Local Streets are considered. 203.04

203.04.01

SURVEY CONTROL/FIELD SURVEYS Introduction

Each project requires initial field surveys to establish baseline topographic information for project scoping and design. Setting horizontal and vertical control is of great importance in mapping. Relative position in the horizontal plane is maintained by horizontal control. Horizontal control consists of a series of points accurately fixed in position by distance and direction in the horizontal plane. For most topographic surveying, traverses furnish satisfactory control. For strip maps, the open traverse is used. The open traverse can be tied to fixed points at each end. For area maps, the closed traverse is used. The closed traverse can be closed to form a net which is accurate to the degree required. Relative position in the vertical plane can be maintained by a series of benchmarks in the map area. These benchmarks are referred to a known datum, usually mean sea level.

203.04.02

Horizontal Control

The current inventory of horizontal control points established in the vicinity of the project will need to be investigated. The Abu Dhabi Municipality and Town Planning Department should be consulted on the order of accuracy and status of existing primary and secondary control points. The need for setting new horizontal control points will be ascertained from the existing data. A discussion of surveying methods and procedures used to establish new horizontal control points is beyond the scope of this manual and will be covered in a companion Technical Manual on the subject of surveying and mapping. 203.04.03

Vertical Control

There are several vertical datum currently being used for construction in Abu Dhabi. Table 200.07 summarizes the most common vertical datum and the relationship between them. In addition, some Sewerage Projects Committee projects use their own datum, in which + 100.00 meters equals 0.00 meters, New Abu Dhabi Datum. All design work will be referred to the New Abu Dhabi Datum. 203.04.04

Coordinate System

A Coordinate System has been established by Abu Dhabi Municipality Town Planning Department. This Coordinate System shall be used for all surveys. 203.04.05

Field Surveys

Field Surveys will be required on nearly every project to supplement the aerial topography, record underground utility or drainage features, reflect new existing features, provide crosssections and existing pavement elevations at the limits of improvement, obtain building floor elevations and other related information needed for preliminary and final design. Once the horizontal alignment, including applicable alternative alignments, has been established, the roadway centerline will be staked

Part 1 200-14

ROADWAY DESIGN MANUAL – Roads and Bridges in the field to enable close examination of the roadway location by Department representatives and Consultants staff. The staking interval and definition of the project geometrics required will be determined on a project specific basis in consultation with the Municipality Representative. A detailed survey of the existing greenery impacted by the project will be required. The survey will record the location, size and limits of all trees shrubs and flower beds within the limits of improvement. Photographs should be taken to supplement the data. This information will be recorded on drawings and used to investigate alignment adjustments or alternatives that will minimize the removal of greenery. 203.05

In absence of drainage master plans or other pertinent studies to establish area hydrology, the Consultant is responsible to develop/collect hydrologic data. This data is to include: • • •

Note that sources for miscellaneous data are scattered. The Consultant must rely upon the collective experience of design in other similar areas to compile this information.

DRAINAGE SURVEYS

The Consultant is responsible for a comprehensive survey of drainage facilities and conditions and data collection during the predesign activities. The data collection consists of three activities: • • •

field review of existing drainage facilities and identification of flood plains within the project’s “zone of influence” field testing including particle size analysis, scour, etc. review of existing drainage master plans (urban areas), hydrologic studies/data collection (urban and rural areas), and other pertinent studies

The review of the existing drainage facilities should include: • • • • • • •

rainfall measurement (volume and time) at a suitable collection site, such as the airport measurement of area run-off miscellaneous basic data such as soil type, land use, aerial photographs, infiltration, evaporation, solar radiation and oceanography

pump stations outfalls reinforced concrete box structures channels ditches large diameter pipes pumps, etc.

Part 1 200-15


Table 200.06 Procedures for Traffic Studies EXISTING ROADS Primary or Secondary Roads

Intersections

Local Streets

24-hour counts for 7 continuous days for each of four yearly periods: • March, April, May • June, July, August • September, October, November • December, January, February 24-hour manual traffic counts for trucks classified by axle for any three days from the following four days: • Sunday • Monday • Tuesday • Wednesday Afternoon (or morning) and evening intersection peak hour counts summarized in 15-minute increments by direction (left turn, right turn and through movements). Counts taken on Sunday or Wednesday, Monday and Tuesday. Hourly summary of same includes separate totals for: Passenger vehicles, vans, pick-up trucks Buses Trucks by axle count 12-hour manual counts taken from 6 a.m. to 6 p.m. on Sunday, (or Wednesday), Monday and Tuesday. Total hourly volumes shall be recorded. Convert to 24-hour ADT by multiplying the 12-hour volume by 2. This will provide a conservative estimate of the 24-hour ADT. If more accurate volumes are required a 24-hour count should be made.

NEW ROAD Primary and Secondary Roads Local Streets

Determine/analyze the design ADT for new road using area demographics and travel patterns, determine the redistribution of existing traffic volumes and traffic volumes generated by new development that will use the new road(s). Conduct Roadside Interview “Origin Destination Surveys” to estimate the directional distribution of traffic. 12-hour manual counts taken from 6 a.m. to 6 p.m. on Sunday or Wednesday, Monday and Tuesday. Total hourly volumes shall be recorded. Convert to 24-hour ADT by multiplying the 12-hour volume by 2. This will provide a conservative estimate of the 24-hour ADT. If more accurate volumes are required a 24-hour count should be made.

FOR ALL TRAFFIC COUNTS 1. 2. 3. 4.

Counts shall not be taken on special holidays or during events which occur once per year. Counters shall be placed at points of obvious traffic volume changes Manual counts shall be taken at the same place(s) as machine counts. Manual counts shall be used to verify machine counts. Manual and machine counts shall be performed for each direction.

Part 1 200-16


Table 200.07 Summary of Datums Used In Abu Dhabi Reference Level

Admiralty Chart

Admiralty Chart

Abu Dhabi Datums

Abu Dhabi Datums

Datums

Datums

Old

New

Existing

Corrected

Sauti Datums

Meters

Feet

Meters

Feet

Meters

Feet

Meters

Feet

Meters

Feet

3.20

10.50

3.50

11.48

2.15

7.05

2.20

7.22

1.90

6.23

1.89

6.20

2.19

7.18

0.84

2.76

0.89

2.92

0.59

1.94

Mean Higher High Water

1.56

5.12

1.86

6.10

0.51

1.67

0.56

1.84

0.26

0.85

Sauti Datums

1.30

4.27

1.60

5.25

0.25

0.82

0.30

0.98

0.00

0.00

Mean Lower High Water

1.19

3.90

1.49

4.89

0.14

0.46

0.19

0.62

-0.11

-0.36

Mean Sea Level

0.95

3.12

1.25

4.10

-0.10

-0.33

-0.05

-0.16

-0.35

-1.15

Abu Dhabi Old Datums

1.05

3.44

1.35

4.43

0.00

0.00

0.05

0.16

-0.25

-0.82

Abu Dhabi New Datums

1.00

3.28

1.30

4.26

-0.05

-0.16

0.00

0.00

-0.30

-0.98

Mean Higher Low Water

0.80

2.62

1.10

3.61

-0.25

-0.82

-0.20

-0.66

-0.50

-1.64

Mean Lower Low Water

0.25

0.82

0.55

1.80

-0.80

-2.62

-0.75

-2.46

-1.05

-3.44

Admiralty Chart Datums Existing

0.00

0.00

0.30

0.98

-1.05

-3.44

-1.00

-3.28

-1.30

-4.27

Mean Lower Low Water at

-0.18

-0.59

0.12

0.39

-1.23

-4.04

-1.18

-3.87

-1.48

-4.86

-0.30

-0.98

0.00

0.00

-1.35

-4.43

-1.30

-4.27

-1.60

-5.25

Bench Mark on Plinth of ADPC Building Mean Higher High Water at Springs near Solstices

Spring Near Solstices Admiralty Chart Datums Corrected

Part 1 200-17


ENVIRONMENTAL CHECKLIST Project:

Date:

Page 1 of 4

1 Water:

Yes Will the proposal result in:

Changes in currents, or the course of direction of water movements, in either marine or fresh waters? Changes in absorption rates, drainage patterns, or the rate and amount of surface water runoff? Alterations to the course or flow of flood waters? Change in the amount of surface water in any water body? Discharge into surface waters, or any alteration of surface water quality, including but not limited to temperature, dissolved oxygen or turbidity? Alteration of the direction or rate of flow of ground waters? Change in the quantity of ground waters, either through direct additions or withdrawals, or through interception of an aquifer by cuts or excavations? Deterioration in ground water quality, either through direct injection, or through the seepage of leachate, phosphates, detergents, waterborne viruses or bacteria, or other substances into the ground waters? Reduction in the amount of water otherwise available for public water supplies? 2 Landform: Will the proposal result in: Unstable earth conditions or changes in geologic substructures? Disruptions, displacement, compaction or overcovering of the soil? Change in topography or ground surface relief features? The destruction, covering or modification of any unique geologic or physical features? Any increase in wind or water erosion of soils, either on or off the site? Changes in deposition or erosion of beach sands, or changes in siltation, deposition or erosion that may modify the bed of the ocean, bay, or inlet? Changes in deposition or erosion or changes in siltation, deposition or erosion that may modify the channel of a wadi or stream, or the bed of a lake? Placing fill below the ordinary high water mark of wadis and streams? Cut or fill placement through swamps, marshes, bogs, and other similar areas that are frequently inundated or saturated by ground water? Part 1 200-18

No

Maybe


Page 2 of 4

Yes

3 Vegetation:

Will the proposal result in:

Change in the diversity of species, or numbers of any species of flora (including trees, shrubs, grasses, crops, microflora, and aquatic plants)? Reduction of the numbers of any unique, rare, or endangered species of flora? Introduction of new species of flora into an area, or a barrier to the normal replenishment of existing species? 4 Wildlife:


Changes in the diversity of species, or numbers of any species of fauna (birds, land animals including reptiles, fish and shellfish, benthic organisms, insects, or microfauna)? Reduction of the numbers of any unique, rare, or endangered species of fauna? Introduction of new species of fauna into an area, or result in a barrier to the migration or movement of fauna? Deterioration of existing fish or wildlife habitat? 5 Agricultural Lands:


Reduction in the quality or quantity of usable farm land? Reduction in the quality or quantity of usable grazing land? 6 Natural Resources:


Increase in the rate of use of any natural resources? Depletion of any nonrenewable natural resource? 7

Economics:

Will the proposal affect local employment, taxes, property values, etc.? 8 Public Services: Will the proposal have an effect upon, or result in a need for new or altered services in any of the following areas? Mosques? Cemeteries? Fire protection? Police protection? Schools? Parks or other recreational facilities? Maintenance of public facilities, including roads? Health Services? Other Services?

Part 1 200-19

No

Maybe


Page 3 of 4

9

Yes

Antiquities/Historical: Will the proposal result in an alteration of a significant archaeological or historical site, structure, object, or building?

10 Air Quality:


Increased air emissions or deterioration of ambient air quality? The creation of objectionable odors? 11 Noise:

Will the proposal increase existing noise levels?

12 Light & Glare:

Will the proposal produce new light or glare?

13 Land Use:Will the proposal result in the alteration of the present or planned land use of an area? 14 Hazardous Conditions: Does the proposal involve a risk of an explosion or the release of hazardous substances (including, but not limited to, oil, pesticides, chemicals or radiation) in the event of an accident or hazardous condition? 15 Population:

Will the proposal:

Alter the location, distribution, density, or growth of an area? Affect racial or ethnic groups including minority, elderly, or low income? Split neighborhoods, or separate residences from commercial facilities? 16 Housing: Will the proposal: Affect existing housing (including, but not limited to, rural or urban residences and business or commercial buildings)? Create a demand for additional housing? 17 Transportation/Circulation:


Generation of additional vehicular movement? Generation of additional movement of bicyclists or pedestrians? Impact on existing parking facilities, or demand for new parking? Impact upon existing transportation systems? Alterations to present patterns of circulation or migration of people and domestic animals? Alterations to waterborne, rail, or air traffic? Increase in traffic hazards to motor vehicles, bicyclists, or pedestrians?

Part 1 200-20

No

Maybe


Page 4 of 4

Yes

18 Energy: Will the proposal result in: Use of substantial amounts of fuel or energy? Require the development of new sources of energy? 19 Utilities:

Will the proposal result in a need for new systems, or alterations to the following utilities:

Power or natural gas? Communications systems? Water? Sewer or septic tanks? Storm water drainage? Solid waste collection and disposal? 20 Human Health:

21 Aesthetics:

Will the proposal result in the creation of any health hazard or potential health hazard? Will the proposal result in:

The obstruction of any scenic vista or view open to the public? The creation of aesthetically offensive site open to the public view? 22 Recreation:

Will the proposal impact upon the quality or quantity of existing recreational opportunities?

23 Severance:

Will the proposal disrupt the cohesive nature of the community it resides in?

Will public services be severed from a particular physiographic segment of the community or a particular population? Will emergency service routes be disrupted by the proposal? Will a particular segment of the community be without service or suffer from longer response times due to rerouting of emergency assistance?

Part 1 200-21

No

Maybe


SECTION 300 DESIGN CONCEPT REPORT 301

CONTENTS

The Abu Dhabi Municipality Road Section requires the preparation and approval of a Design Concept Report (DCR) prior to commencing final project design. The report is to be prepared under the direction of an experienced engineer designated by the Municipality. Part 1, Section 200, Design Concept Development, includes a discussion of the background information and data collection activities necessary to develop the design concept. Part 1, Section 300, Design Concept Report, contains a discussion of the specific requirements and content of a DCR. The role of a DCR is to summarize the needs, alternatives, costs, and overall impacts of the proposed roadway or bridge project. The scope of the project is defined and the design criteria identified. The DCR is the project scoping document and the basis for selecting the project design. The basic roadway configurations shown in the DCR will be carried forward to the final design phase.

The preliminary engineering activities associated with the DCR involve preparation of numerous technical studies and reports, many of which are initiated in the data collection phase as described in Part 1, Section 200, Design Concept Development. These are prepared as stand alone documents and are included as an Appendices to the DCR. The DCR will summarize the results of these individual reports under the respective topic included in the DCR Table of Contents (See text box). Furthermore, the discussion under each topic will address interdisciplinary relationships necessary to coordinate all technical aspects of the design concept. The sections that follow provide guidance for the development of the technical studies and requirements for presentation of the material in the DCR. 301.01

The DCR will prepare and packaged as follows: • • •

DCR Table of Contents • • • • • • • • • • • • • • • • • • • • • •

Executive Summary Introduction Traffic Analysis Description of Alternatives Design Data Typical Sections Geometrics Interchange/Intersection Configurations Parking Study Hydrology and Hydraulics Subsurface Investigations Bridge Type Selection Utility Impact Analysis Socioeconomic Analysis Agriculture Impact Public Feedback Signing and Pavement Markings Lighting Construction Staging Cost Estimate Conclusion/Recommendations Drawings, Plans, Profiles, Typical Sections and Architectural Features

FORMAT

DCR (Volume I) - Written portion of the report bound separately in A4 size. DCR (Volume II) - Drawings that accompany the report bound separately in A3 size. DCR (Appendices) Technical Memorandums, Studies and Reports bound in A4 size. For smaller projects the documents should be bound together. Larger projects may require separate packaging of the reports, titled as Appendix A, Appendix B, etc.

Each document will include the following information on the cover: • • • • • •

Municipality of Abu Dhabi, Road Section Design Concept Report Volume No. or Appendix No. Project Name and Route No. Project Number Vicinity Map Schematic with Project Termini noted Consultant Identification

• • See Figure 300.01 to be used as the standard cover sheet for the DCR.

Part 1 300-1


Location / Design Concept Study Project Location

Final Report Project No.

15 May 1997

Prepared by Preparer’s Logo

Client Logo

De Leuw Cather & Co. th

3875 N. 44 Street, Suite 250 Phoenix, AZ 85018 Figure 300.01 Standard Design Concept Report Cover Sheet

Part 1 300-2

Prepared for

Abu Dhabi Municipality

ROADWAY DESIGN MANUAL – Roads and Bridges 302

EXECUTIVE SUMMARY

The Executive Summary is a short (2-4 pages) recapitulation of the DCR document. The Summary should address the following key topics: • • • • • •

Purpose and Need of the Project Alternatives Evaluated Recommended Design Concept Major or Controversial Issues Estimated Cost Conclusion

Traffic signal recommendations will be included in the report. For each signal location, the following information should be provided:

It is not necessary to address every aspect or technical consideration that is discussed in the main body of the report. The summary should focus on items presented in the report that are of critical interest to the Municipality such as an accurate concise description of the recommended design concept and the estimated cost. It should be clearly stated how the recommended design responds to the purpose and need of the project. Both the major benefits (i.e. improve traffic circulation, improve intersection safety) and the adverse impacts (i.e. displacement of coastal vegetation) should be summarized.

303

INTRODUCTION

The introduction is to prepare the reader for the subject matter that will follow in the body of the report. It should only be a few paragraphs in length and should provide a brief description of the project as well as the reason for preparing the Design Concept Report. The project description should be very general and should identify the project’s location, the agency/municipality in charge of its implementation, and the source of funding that will be used for its design and construction. A statement can also be included that identifies how the project fits into the overall transportation infrastructure of the area.

304

lanes, auxiliary lanes, turning lane requirements including storage lengths, signal warrants, level of service and capacity. Schematic diagrams of the roadway segments and intersections should be used to display the data. This information will be presented in the DCR along with a summary of the project traffic data including current and forecasted ADT values, peak hour and peak hour directional splits and percent of trucks.

TRAFFIC ANALYSIS

The collection of traffic data and the traffic projection procedures are discussed in Part 1, Section 203.03, Traffic Counts. The data will be used to analyze and shape the various alternatives and geometrics. This is an iterative process that results in identification of the number of through

• • • • • •

Phasing Diagram Controller Equipment Detection requirements CCTV Interconnection Power Source

On all projects where the primary justification, or an important justification, of the project is to improve safety, the DCR should include accident history data and an analysis of the causes of the accidents as well as a collision diagram. Estimates should be made of the accident reductions expected if the improvement proposal (or alternatives) is built. The monetary value of the accident savings should be calculated over the design period of the project (normally 20 years where geometric improvements are proposed). A summary of the traffic analysis shall be included in the body of the DCR. The complete report is also included as a separate Appendix.

305

DESCRIPTION OF ALTERNATIVES

In consultation with the Municipality, the engineer shall develop alternatives to be evaluated that respond to the project purpose and need to varying degrees. The alternatives identified may include separate horizontal alignments, profile variations, typical section concepts etc., that can be evaluated in a matrix form to qualitatively and quantitatively review the alternatives to identify major differences. The engineering, social, economic and natural environmental impacts for each alternative under consideration must be addressed.

Part 1 300-3

ROADWAY DESIGN MANUAL – Roads and Bridges The horizontal alternative alignments will be displayed on aerial photographs for evaluation of associated impacts. The sheets will show the proposed centerline, stationing, proposed structures, edge of pavement lines and affected properties, at a scale that is appropriate to the project length and character. A cost estimate will be prepared for each alternative and include: • • •

Construction costs Utility relocation works costs Land acquisition costs

At this point, meetings will be held with various Municipality and Government Departments that have a vested interest in the project. The engineer will present the alternatives, review the evaluation criteria and matrix form and discuss merits and adversities of the different alternatives. Comments and direction received at the meeting(s) will be factored into the alternatives evaluation matrix. Finally, the analysis will conclude with a discussion of the evaluation criteria for each matrix parameter, input/direction received concerning the project and a summary discussion of the advantages and disadvantages of each alternative studied. This will be followed by the engineer’s recommended alternative with supporting justification for the selection.

306

DESIGN DATA

This section will document the design criteria associated with the recommended design concept and specifically identify any exceptions from the minimum criteria established for the roadway classification. It is very important that sufficient detail is included in the DCR so that future revisions to basic design features and project scope are held to a minimum. The following basic design criteria established in Part 2, Roadway Design, shall be included: •

the functional classification of the road per Part 1, Section 100, General Information.

•

•

• • • • • •

the minimum design speed(s), min. horizontal/vertical curve radii, sight min. distance (passing and stopping), max. superelevation and other design requirements associated with the classification of the road; the actual design speed(s), horizontal/vertical curve radii, sight distance (passing and stopping), superelevation, etc. used for the project; lane width, shoulder width, and bridge width; on the project cross slope; grade; horizontal and vertical alignment (actual); horizontal and vertical clearance; and, bridge structural capacity.

The design exceptions identified shall be prepared in a “Fact Sheet” format as described in Part 2, Section 100, General Design Criteria.

307

TYPICAL SECTIONS

The typical roadway cross sections and the dimensions of the lanes, shoulders, median(s) for both the mainline and all ramps are to be identified. The number of typical sections will depend on the number of significantly different roadway/pavement structure conditions. At a minimum, at least one section should be provided which depicts all facilities within the limits of the right-of-way (i.e., ramps, frontage roads, drainage channels, etc.). The type of roadway section, i.e., cut or fill, number of lanes, shoulders, pavement structural section, cross slopes, and any retaining walls are also to be included. Drawings that illustrate this information are to be included in the Appendix to the DCR.

308

GEOMETRICS

The alignment, profile, and number of traffic lanes, including through lanes, auxiliary lanes, turning lanes and ramp lanes are to be plotted on an appropriately scaled plan. A scale of 1:500 should be used for urban projects and 1:2500 for rural projects. The alignment should be displayed on an aerial base and the corresponding roadway profile shown below in a split sheet format.

Part 1 300-4

ROADWAY DESIGN MANUAL – Roads and Bridges The text in this section should include a narrative description of the geometrics, constraints, controlling factors, drainage considerations and reference to the design exceptions. The plans are to be attached as an appendix to the DCR.

The results of the study shall be summarized in the body of the DCR, with the entire study included in the Appendix.

309

• • • •

INTERCHANGE/ INTERSECTION CONFIGURATION

The various types of traffic interchanges are described in Part 2, Section 500, Interchanges. The discussion in this section should identify the site and project considerations which led to the selection of the interchange and intersection type.

The summary of the results shall include:

• • • •

The site considerations include: • • • • • •

• the constraints imposed by the existing and nearby transportation facilities proximity of adjacent interchanges the standards and arrangement of the local street system including traffic control devices right of way controls local planning community impact, and cost topography.

The project considerations include: • • • • •

the speed, volume, and composition of traffic to be served the number of intersecting legs crossing and turning conflicts safety considerations cost

The interchange/intersection alternatives should be evaluated as a part of the alternatives analysis described in Part 1, Section 305, Description of Alternative, when viable options are identified for the particular project. This is especially true for freeway and expressway projects where the Interchange/Intersection type has a significant impact on the project character, capacity and cost.

310

•

the existing parking demand the anticipated parking demand the resulting parking shortfall (or excess) the alternatives as to how the project can provide adequate parking cost comparison of parking alternatives economic impact of inadequate parking if required by the roadway classification, the need for off-street parking facilities the costs and right-of-way requirements associated with each of the above alternatives the recommended alternative to meet the anticipated parking demand, the conceptual design of the recommended alternative (see Part 2, Section 211, Parking).

311

HYDROLOGY AND HYDRAULICS

The Design Concept Report shall include a separate section (study) for drainage design concepts, which shall also include, when required, separate reports for flood plain encroachment and major waterway crossing studies. The drainage design concepts section shall address the following items: •

Planning consideration for the overall watershed considering the project and other existing and future development

•

Assessment of existing and future conditions affecting drainage areas, flow patterns, and flood levels

•

Estimate of future development and its effect on flows and flood levels

•

Drainage map showing topographic features, watershed boundary, slope contours, drainage areas, existing drainage systems, proposed cross-drain locations (including peak flow volume, design high water elevation and culvert size) and proposed conveyance

PARKING STUDY

In accordance with Part 1, Section 202.09, Parking Requirements, a parking study shall be prepared and included as part of the DCR. Part 1 300-5

ROADWAY DESIGN MANUAL – Roads and Bridges systems (pipes and channels including flow direction, sizes and peak flow volume) •

Hydrology calculations for drainage area intercepted by the project to include peak runoff volume flow rates from each drainage area

•

Proposed concepts for disposal of storm water.

•

Design criteria, procedures, methodology, and assumptions for analysis and design.

•

Proposed concepts for handling and disposing of storm water during construction.

•

Recommended size and location of cross drainage structures and channels, including design high water elevation that might affect the road profile grades or the roadway location.

•

Proposed concepts for on-site roadway drainage collection, detention, and outfall locations.

•

Separate Flood Plain Study Report where the roadway encroaches on flood plains either longitudinally or transversely.

•

Bridge Location and Hydraulics Report for bridge or large box culvert waterway crossings.

311.01

PURPOSE

The purpose of the drainage design concept study is to document the methodology and results of the hydrologic analysis and the rationale used in developing the roadway drainage system. It shall define the type, size, and location of cross drainage structures and channels, and determine flood level elevations. The drainage design concept study shall determine the initial type, size and location of the onsite roadway drainage system and determine outfall location(s). It shall also address any floodplain encroachments and the overall watershed planning.

311.02

PLANNING & PREPARATION OF THE DRAINAGE DESIGN CONCEPTS

The Municipality often is and should be perceived as a developer of transportation facilities that have the potential to stimulate secondary activity along the transportation corridor just as a major residential development can stimulate commercial activity. Accordingly, there is a requirement to address overall stormwater management needs in conjunction with existing and future developments planned for the foreseeable future. Because the transportation corridor often traverses several watersheds, the development of an adequate stormwater management plan can be severely fragmented and significant problems created if there is a lack of coordinated planning among concerned parties. To be truly effective, a stormwater management plan should consider the total scope of development (i.e. transportation, residential, commercial, industrial and agricultural). Department coordination with responsible Agencies and other Departments is essential to ensure that proposed facilities match existing ones, and that they are consistent with the longterm needs of the area. Significant savings can often be realised by planning overall combined stormwater management facilities, even though the roadway development is only a small part of the total system. In addition, the Municipality can provide important information to other Agencies and private developers wishing to develop a comprehensive stormwater management plan without assuming responsibility for the planning and decision making process for the entire watershed. Accordingly, prior to design, a level of planning and coordination shall be undertaken by the designers that will properly locate facilities and adequately address the overall drainage needs of the overall watershed(s) in regards to existing and future (foreseeable planning) development. This section provides general guidelines and major considerations for evaluating these factors during the planning process.

Part 1 300-6


aesthetically objectionable, and disrupt flow and navigation.

Problem Categories

Planning for drainage and stormwater management facilities should include a consideration of the potential problems associated with stormwater quality and quantity. Several categories of data should be obtained and evaluated including: • • • • • • • •

Runoff quality provisions Runoff quantity determination Flood plain delineation Inventory of problem and future developments Development of alternative plan concepts Consideration of multipurpose opportunities and constraints Hydrologic and hydraulic analysis of alternative concepts Benefits analysis and evaluation

These are further defined as follows: A. Quality: Several broad categories of degradation have been developed to delineate or describe levels of stormwater impacts: •

•

•

•

Aesthetic deterioration: Undesirable general appearance features (dirty, turbid, or cloudy) and actual physical features (odors, floating debris, oil films, scum, or slime) are present. Dissolved oxygen depletion: When the oxygen demand of bacteria is stimulated by the organics, the subsequent reduction in oxygen levels can disturb the balance between lower forms and the food chain. Unoxidized nitrogen compounds (ammonia) can also cause problems. This is of concern when discharging into reservoirs, small, limited flush, tidewater areas, and freshwater streams. Pathogen concentrations: High concentrations of several pathogens can reduce the acceptable users of the receiving waters. A concern where discharge may be accessed for domestic use and discharge near public use areas (bathing beach). Suspended solids: The physical build-up of solids can cover productive bottoms, be

•

Nutrients: Accelerated eutrophication that stimulates growth of aquatic vegetation can cause a water body to become aesthetically objectionable, deplete dissolved oxygen, and decrease recreational value by creating odor and overgrowth. Advanced eutrophication can lead to sediment build-up, which reduces storage capabilities.

•

Toxicity: The two types of toxics generally found in stormwater (metals and pesticides/persistent organics) may build up in sensitive areas over the long term. At high levels, they can have serious shock effects on aquatic life. Low levels can become significant by accumulation up the food chain.

Quantification of the levels of contaminants that are being washed off a roadway is complicated by the variable effects of and the periods between storm events. The contributory factors are rainfall intensity, street surface characteristics, and particle size. The varying interaction of these factors makes it difficult to precisely estimate the impact that discharge will have on water quality. However, where it is suspected that periodic runoff may have a serious quality effect upon the receiving area, further investigation, analysis and methods for solving the problem should be presented for review and approval. The quality control management procedure particularly applicable to this region would consist of diverting the first 8 to 10 millimeters of runoff into retention (often combined with detention for peak quantity control) basins where the more concentrated contaminates and sediments can be contained. The volume of stormwater is then allowed to dissipate slowly by seepage and evaporation, effectively trapping the contaminates in the basin for periodic cleanout and disposal in a sanitary land-fill as needed. An exception is erosion and sediment control, which is often a significant component of stormwater quality. In general, erosion and sediment transport should be limited by

Part 1 300-7

ROADWAY DESIGN MANUAL – Roads and Bridges developing and implementing an erosion and sediment control plan which addresses both temporary and permanent control practices. B. Quantity: Determinations of stormwater quantity are primarily useful for evaluating and mitigating the impact of a project. Without detention, land development increases peak runoff rates and volumes from storm events, which can lead to higher flood elevations. Appropriate hydrologic and hydraulic calculations presented in various chapters of this manual should be made to determine the required conveyance through the Municipality’s project limits, and to aid in mitigating impacts to downstream structures and development. Procedures contained in Part 2, Section 700, Roadway Drainage Design, should be used to evaluate the ability of a facility to accomplish the following controls for a particular area: •

Provide positive drainage and runoff collection to the minimum criteria for safe passage of traffic on the project roads and parkings.

•

Reduce runoff rates when applicable by increasing infiltration, and by storing precipitation and runoff where it falls and releasing it slowly.

•

Protect areas subject to flood damages by keeping runoff confined to drainage facilities such as pipes or channels and by building appropriate flood control facilities.

•

Maintain offsite flows, through the project area.

•

Limit flood plain enroachment to acceptable upstream/downstream flooding impacts.

The following questions should be considered when selecting the plan for disposal of stormwater runoff: 1. Are existing drainage systems large enough to handle runoff? 2. Are runoff estimates consistent with adopted drainage plans and Municipality criteria?

3. Will the project require retention or detention storage areas to mitigate the impacts of increased runoff, or can the increase be handled by other project features? 4. Is there sufficient area to construct a retention or detention storage within the project limits? Are alternative sites available for storage of stormwater? 5. What are the groundwater and soil conditions? Is there a high groundwater table, or are there impermeable soil layers? C. Flood Plain Encroachment: The primary drainage consideration for facility location in highway planning is the evaluation of the impact of flood plain encroachment for a steam or wadi crossing or where the road embankment longitudinally encroaches into the flood plain area. The following factors for locating a stream crossing that involves encroachment within a flood plain area: • Waterway characteristics (stable unstable) • Geometry • Hydrology • Hydraulics • Alignment • Flood plain flow • Needs of the area • Economic and environmental concerns

or

A detailed evaluation of these factors is part of the bridge location and hydraulics study. When a suitable crossing location has been selected, specific crossing components can then be determined. When necessary, these include the geometry and length of the approaches to the crossing, the probable type and approximate location of the abutments, the probable number and approximate location of the piers, the estimated depth to the footing supporting the piers (to protect against local scour), the location of the longitudinal encroachment in the flood plain, the amount of allowable longitudinal encroachment into the main channel, and the required river training works, to ensure that river flows approach the crossing or the encroachment in a

Part 1 300-8

ROADWAY DESIGN MANUAL – Roads and Bridges complementary way. Exact information on these components is usually not developed until the final design stage. Where the roadway embankment encroaches significantly in a longitudinal direction into the flood plain, a separate floodplain encroachment study must be made to evaluate the increased flood depths and velocities that may impact, upstream and down stream properties. Further details defining flood plain encroachment are provided in Section 311.02.02. D. Other Departments Coordination: Coordination between concerned agencies during the project planning phase will help produce a design that is more satisfactory to all. Substantial cost savings and other benefits frequently can be realized for both the roadway and other development projects through coordinated planning between the various Government Departments and private developers. 311.02.02

Flood Plain Encroachment and Risk Evaluation

When a highway project will encroach on a flood plain, careful consideration must be given to the potential risks from the encroachment. Any proposed project that encroaches on a flood plain either transversely or longitudinally, and is predicted to result in a significant adverse impact on natural flood plain values, a significant increase in flood risk, or a significant change in the potential for interruption of main access roadways, emergency service or major services, must be evaluated with a complete hydraulic analysis and a risk analysis, to be included in a separate flood-plain study or a bridge location and hydraulics study for transverse crossings. These separate reports must document considerations of alternatives which do not include such encroachments. Significant encroachments will not be approved unless there is no practical alternative. The flood plain study (and/or bridge location and hydraulics study) shall include the following: A. Hydraulic Analysis: The hydraulic analysis must provide the water surface profile elevations

before and after the proposed project in both the upstream and downstream directions for a distance to where it can be shown that no further impact over pre-project conditions is influenced by the project for: (i) the design event storm, (ii) for the 100 year storm, and (iii) the maximum probable storm (usually the 500 year event). Besides the peak water surface profile, the analysis shall include the flow volumes, velocity profiles (velocity at various points in the crosssection), and hydraulic structural alternatives that were evaluated to mitigate significant encroachment. The frequency with which the highway or watershed divide is likely to be overtopped should be stated. If the overtopping flood is a 500-year flood or greater, it should be stated. The location of the overtopping should be indicated. B. Economic Analysis: An economic analysis should include a comparison of design alternatives, using expected total costs (construction costs plus risk and damage costs) to determine the alternative with the Least Total Expected Cost (LTEC). The comparison will include probable flood-related costs during the service life of the facility for: highway operation, maintenance, and repair; highway-aggravated flood damage to other property; and additional or interrupted highway travel. Other costs include crop damage, structure damage and public inconvenience. C. Study of Flooding Encroachments: The flood plain study should include an inspection of the flood plain to determine the increase in the number of flood receptors and the increase in the damage to present flood receptors that will result from the expected increase in flood heights. Consultation with local citizens and other Departments should be initiated where necessary to adequately assess encroachments. D. Risk Assessment: All designs with flood plain encroachments should include an evaluation of the inherent flood-related risks to the highway facility and to the surrounding property. In the traditional design process, the level of risk is seldom quantified, but is instead implied through the application of predetermined design standards. For example, the design frequency, backwater

Part 1 300-9

ROADWAY DESIGN MANUAL – Roads and Bridges limitations, and limiting velocity are parameters for which design standards can be set. Two other approaches, however, are available that quantify risk on projects that involve highway facilities designed to encroach within the limits of a flood plain. These are risk assessment and economic analysis. Risk assessment is a subjective analysis of the risks engendered by various design alternatives, without detailed quantification of flood risks and losses. It may consist of developing the construction costs for each alternative and subjectively comparing the risks associated with each alternative. Economic analysis (sometimes called risk analysis) encompasses a complete evaluation of all quantifiable flood losses and the costs associated with them for each structure alternative. This can include damage to structures, embankments, surrounding property, traffic-related losses and scour or stream channel change. The level of expense and effort required for an economic analysis is considerably higher than for a risk assessment, and selection of the process to be used should be based on the size of the project and the potential risk involved. A risk assessment is usually more appropriate for small structures or for structures whose size is highly influenced by non-hydraulic constraints. Policy dictates that hydraulic facilities be designed so that highway facilities will perform without significant damage or hazard to people or property during the appropriate standard design frequency flood. Risks associated with floods of magnitudes greater than the standard design frequency flood should be evaluated in accordance with the risk evaluation levels presented in this section. If warranted, a design based on a lower or higher frequency flood may be used. The minimum design frequency for bridges on main highways, however, is 50 years. A typical example would be a major cross drain box culvert for a primary highway. The standard design frequency would be a 50-year frequency flood. A design based on this frequency should be produced in the "traditional" manner, including development of feasible alternatives. The alternatives would be compared for cost and for risks associated with the 50-year frequency flood. The lowest total cost structure that met the design

constraints would be the preferred design. This design should then be investigated for the 100year flood. 311.02.03

Data Collection

Identification of drainage data needs should be a part of the early planning phase of a project, when appropriate procedures for performing hydrologic and hydraulic calculations are selected. Several categories of data may be relevant to a particular drainage project, including published data such as precipitation, soils, land use, topography, streamflow and flood history. Published mapping is usually inadequate, so field investigations and surveys are necessary to determine drainage areas, identify pertinent features, obtain high water information, survey lateral ditch alignments and survey bridge and culvert crossings. In addition, hydrology calculations for a watershed or larger drainage area will usually require some sort of topographic mapping. The preferred mapping is using aerial photography showing contour elevations using digital techniques is preferred. Manual ground surveys are usually adequate for smaller areas. The requirements in more detail are as follows: A. Data Collection Procedure: Drainage data should be collected before calculations are initiated, under the following general guidelines: 1. Identify data needs, sources, and uses. Much of this information will have to be provided in the concept report and kept in the supporting files. 2. Collect published data, based on sources identified in Step 1. 3. Compile and document the results of Step 2, and compare data needs and uses with published data availability. Identify any additional field data needs. 4. Collect field data based on needs identified in Steps 1 and 3. 5. Compile and document the results of Step 4. B. Published Data: At present, there is limited published data with regards to soils, land use,

Part 1 300-10

ROADWAY DESIGN MANUAL – Roads and Bridges streamflow, flow histories, etc; however, a thorough search for soils investigation records and existing utility/drainage systems should be made from as-builts of other projects in the vicinity. Old newspaper records may also be a source of timing and pictures of past flooding events. C. Drainage Areas: If there is sufficient topographic information for a project site from readily available sources (aerial mapping), a field determination of drainage area may not be necessary, but spot-checking selected control elevations is always advised. For those project sites for which detailed information is not available, field survey work or aerial photo mapping should be performed. In all cases, a site visit by the designer is mandatory to confirm drainage area conditions. Drainage areas shall be outlined on the drainage map (preferably on a contoured photo base map). Drainage area boundaries should connect with the job centerline, typically at high points in grade or at other locations where there is a definite division in the direction of storm runoff flow. After the overall areas are plotted, the drainage area should be sub-divided to show how the various sections contribute to the structures in the proposed drainage or storm drain system. All drainage area boundaries should be followed from project centerline around the area being covered and closed again to the roadway centerline. Ridges that do not establish an area draining to the project should not be shown unless pertinent to determination of runoff concentration points or flow path segments. Exceptions to the rule for closing all drainage area boundaries to centerline are to be indicated clearly on the map by notation. These notations should show location and elevation of breakover or diversion to or from the drainage area. Typically, a drainage area should close to each existing culvert along the project, for each probable cross drain location to each inlet for piped system, and protected overland flow entrances to channels. As an exception, where two or more structures operate conjunctively to drain a single area, flow distribution information should be noted.

For urban type construction surveys, appropriate city maps or specially prepared maps should be marked to show the boundaries of total areas contributing to the project. Streets or other drainage facilities in these areas should be marked with flow arrows. In many instances, elevations may have to be determined to accurately delineate direction of flow in gutters or side of road channels. All areas contributing to existing storm drains which drain to or across the project should be shown. In very flat terrain, it is often necessary to develop profiles for cross streets and parallel streets to make a definite determination of drainage areas. Specially flown aerial photography should be obtained for most construction projects. Elevation contours and ridge lines usually can be indicated on the photographs utilizing digitized cartography combined with ground based control surveys. When photographs are used, the field survey party should verify questionable points and supplement the information with structure sizes, elevations, and elevations as required. Drainage areas can also be determined by stereo interpretation of stereo paired photographs with spot field survey work as appropriate (usually sufficient for smaller areas). D. Drainage Maps: For roadway projects, the drainage maps should be prepared on preformatted sheets that use a cross section grid printed across the lower portion for plotting the project profile. The profile is plotted to some convenient scale according to need. For projects involving interchanges, rest areas, urban streets and the like, a supplemental drainage map that shows only the plan portion on a sheet without a profile grid is required. The supplemental map is provided to show the small areas needed to calculate pipe sizes for the tabulation of drainage structures within these special areas. The following data should be provided on the plan portion of the map: 1.

Part 1 300-11

Physical land features affecting drainage, such as elevation contours, land use, vegetation cover, streams, wadis, reservoirs and tidal areas, together with past high water

ROADWAY DESIGN MANUAL – Roads and Bridges and date of occurrence, if available, and present water elevations with the dates of the readings, as appropriate. 2.

3.

Existing drainage structures, showing type, size, flow line, flow direction, and any other pertinent data. Drainage divides and information, where applicable, to indicate the overland flow of water. Drainage areas on maps of urban and rural sections should be shown to the accuracy necessary, depending on the system involved. A guide to the appropriate accuracy for a non-critical system is provided. Critical systems usually require a drainage area determination within 2 to 3 percent.

Size Drainage Area (Hectares) 0.0 - 0.2 0.2 - 2 2-4 4-8 8 - 20 20 - 40 40 - 80 >80

Accuracy Mainly Impervious (Hectares) 0.02 0.04 0.08 0.2 0.4 0.8 2 4

Mainly Pervious (Hectares) 0.04 0.08 0.2 0.4 0.8 2 4 10

Inserts are used to show areas of such magnitude that the boundaries cannot be plotted at the regular scale. Proposed drainage structures are plotted by symbol only in the plan portion and noted by structure number. 4.

5.

6.

Aerial photography is desirable because it will document the development and often the drainage pattern which existed at the time of design. Design, base, and overtopping (or maximum probable flood) discharge and stage values are required on all expressway and mainroad projects for all cross structures that would back floodwater outside the project limits, regardless of structure size.

In the report, the various cross-drain culverts should be summarized by station, size, invert elevation and minimum culvert backfill values for pH, resistivity, sulphates, and chlorides for the various alternate culvert materials.

The profile portion of the map should include the following data: 1.

Plot of the existing ground, done in a light solid line to the same horizontal scale as was used for the plan portion.

2.

Drainage map sheets with the profile blocks deep enough to sufficiently show the necessary profiles and cross-drain profiles.

3.

Plot of the proposed profile grade line.

4.

Plots of all proposed special ditches, except median, when horizontal and vertical scales permit.

5.

Plots of proposed cross drains, except median drains. Skew and pipe slope are not shown.

6.

For urban projects, plot only the storm drain and mainline structures. Laterals are not plotted. Flow line elevations are posted along the main.

E. Existing Features Survey: In areas draining to a project site, all streams, wadis, ditches, reservoirs, drainage structures, and other possible conflicting utilities should be shown. Flow lines, controlling grade elevations, and high water stages should be documented for existing structures. The concept report should note record the estimated reliability of flow and high water observations. 1. Survey Notes: The drainage survey notes should show all pipe lines, culverts, and bridges in place on the existing roadway. Pipe length, size, type, and conditions should be given. The design for alternate culvert materials requires accurate information on the condition and length of service for existing culverts. Data on corrugated pipe should include material (steel or aluminium), coatings, size, and type (annular or

Part 1 300-12

ROADWAY DESIGN MANUAL – Roads and Bridges spiral) and size of corrugation. Flow line elevations of pipes should be shown at both inlet and outlet. For box culverts to be extended, an accurate sketch should be made showing the size and length of the culvert, thickness of all walls, wings, and slabs, and the angle of the barrel with the survey centreline. Elevations should be given on the top of the bottom slab, top and bottom of top slab, parapet walls, wings, etc., on each end of the culvert. The type, length and width of roadway, location of bents, number of piles per bent and type of footings should be shown for bridges in place. Profiles should be shown as centerline of roadway, from the edge of pavement left and right of centerline of survey, and under the bridge on centerline of survey. The profiles should accurately define the top and bottom of channel banks and the channel bottom. 2. High Water Information: Reliable high water information is necessary to evaluate flood elevations and establish roadway grades. High water elevations should be shown upstream of the proposed project, upstream of significant existing structures, and at some point along or at the end of outfall ditch surveys. The location at which a high water elevation is taken should be clearly recorded in the field notes, along with the date and time if available. At many locations, it is not possible to obtain documents information on high water. In such cases, elevation may be estimated by observation of natural growth, evasion marks or by other means. The survey crew should provide complete information on the methods used. The crew chief should attempt to obtain information from local residents or maintenance personnel. The soils investigation usually supplies water table information within the project limits; however, the survey crew should note information pertaining to standing water, areas of heavy seepage, or springs within the basin area. 3. Lateral Ditch Surveys: Most highway section projects should routinely include lateral ditch surveys at the locations of existing ditches, streams, wadis, swales, etc. The surveys should provide a clear picture of existing conditions at

any location where water comes to and/or leaves a proposed project. They should clearly show the path and approximate elevations of flow for existing ditches and natural streams. Inflow data should be provided for a distance sufficient to indicate the degree of channelization and the direction of flow, usually a distance of 30 to 100 meters. Data on the outfall portion should extend far enough to determine the direction and degree of channelization and the rate of fall in water surface, and to reach a point of positive and safe disposal. If ditch or channel work appears necessary, collection of topographic data should continue downstream to a point at which damage to adjacent property appears to be insignificant. If the length of an outfall raises serious doubts about its usefulness, the field party should terminate the survey at 150 meters and note the approximate distance to a suitable disposal point. This note should give the distance, the water elevation at the approximate end, and a brief description of the topography (i.e., tidal bay, reservoir, wadi, etc.) into which the outfall will drain if extended. The designers can then determine if a further detailed outfall survey is required. The field survey for a lateral ditch should always include property boundaries or plot walls/fences, which are often the determining factors in the ultimate location of outfalls. With property boundaries marked, the design engineer is in a much better position to determine the extent of cross-sectioning needed to cover possible alterations in alignment, and the design engineer is aware of the limitations in changes he may consider. 4. Bridge and Large Culvert Surveys: Locations of larger culverts and bridges often must be detailed. The meander of both banks of a stream for a sufficient distance upstream and downstream to determine the approximate extent of any probable channel relocation should be obtained. This ordinarily can be shown within 150 meters upstream and downstream from the project. Any major overflow channels also should be indicated within approximately the same limits or within the limits that these channels leave and

Part 1 300-13

ROADWAY DESIGN MANUAL – Roads and Bridges return to the main channel. Meandering channels close to and approximately parallel to the project centerline should be located carefully and crosssectioned. Across flood plains where the proposed project follows an existing fill, cross-sections should extend far enough to provide a record of natural ground profiles right and left of the project. Any washouts or significant swales, side wadiis, sloughs or ditch outlets should be noted clearly in the topography. Recommendations for significant realignment or improvement of an existing channel often will come as part of the structure design, making it necessary to survey a designated location. For this reason, specific channel location surveys should not be made during the initial location survey unless the need for and logical location of such changes are apparent. Required data on existing roadway and railroad structures upstream and downstream should be identified by the drainage engineer so it can be included in the survey. For fills and structures in reasonable proximity to the project, a profile of the existing roadway showing structure openings should be established relative to the project data. For structures farther removed, it is often adequate to include only a profile and high water information. The information should include observations on scour, washouts, or other pertinent hydraulic factors. Where scour is significant, cross-sections should be taken to determine the depth and extent. Appropriate flood elevation data should be obtained for bridges. If reliable data is not available, that fact should be noted by the field party. The extreme high water, its location, and the approximate date of its occurrence should be recorded, if available. Other elevation high water that can be dated should also be recorded when practical. If possible, a "normal" high water elevation, or one which can be expected to recur about every 2 to 3 years, should be determined. A normal elevation that would be expected to prevail through seasons of average rainfall should be recorded.

Field surveys at existing bridges should include three profiles: the first on the survey centerline, the second approximately 10 meters right of the survey centerline, and the third approximately 10 meters left of the survey centerline. The purpose of the second and third profiles is to provide data at the edge of the bridge. The centerline profile should show the roadway grades and the ground line under the bridge. Cross-sections should be taken across the bridge area to furnish elevations for plotting the face of the slopes and for accurate plotting of low water channels. All profiles should include points indicating the top of the low water banks (the edges of the low water channel), water level at the date of the survey, and the profile of the stream bed along the survey lines. Where new lanes for the roadway are to be located at bridges from a survey along the old roadway using cross-sections for approximate elevations, it is necessary that the three profiles be run along each side of the new roadway, furnishing complete channel limits and elevations on each profile. These surveys should include corrected stationing referenced to the road survey, showing station and elevation equalities if necessary. At expressways, where a single profile is run along the centerline of the median for the roadway survey, the three profiles and crosssections should be performed for each lane at all bridges. 5. Documentation: Documentation involves the compilation and presentation of all pertinent watershed data collected for the project. It should include (but is not limited to) basic items such as drainage area and other maps, field survey information, published data references, photographs, and narratives from witnesses of historic floods. This data should be maintained in the permanent records. The orderly compilation and presentation of watershed data will expedite the design, review, and evaluation phases of a drainage project 311.03

STORM WATER HYDROLOGY

To convert precipitation to stormwater runoff, hydrologic calculations are generally used to quantify the abstractions (precipitation losses) which occur as part of the hydrologic cycle. Virtually all drainage and flood plain calculations only consider infiltration, interception, and

Part 1 300-14

ROADWAY DESIGN MANUAL – Roads and Bridges surface storage losses, since short time scales will usually render losses from evaporation and transpiration insignificant. A possible exception to this usage is for land-locked watersheds. Since the governing relationships of hydrology are complex and, unlike problems in engineering mechanics, are not easily solved through direct use of the fundamental laws of physics, a wide variety of hydrologic procedures have been developed. Procedures for making time of concentration and rainfall excess calculations, procedures for estimating peak runoff rates at gaged and ungaged sites, procedures for developing design storm hyetographs, and flood hydrograph and hydrologic channel routing procedures are contained in the drainage volume of the design manual. Drainage studies often follow a similar sequence of calculations for all procedures, because precipitation must be routed through watersheds, channels, and reservoirs. In most cases, stormwater runoff will be estimated using the following general procedure:

7.

Perform downstream channel and reservoir routings, as appropriate.

8.

Record the necessary calculation process and the results on the appropriate drainage maps, and in the drainage section of the Design Concept Report, as appropriate.

311.04

The consideration of open channel hydraulics is an integral part of roadway projects in which artificial channels and improvements to natural channels are a primary concern. Procedures for performing uniform flow calculations that aid in the selection or evaluation of appropriate channel linings, depths, and grades are included in the drainage volume of the design manual. For most artificial channels, the most desirable lining is natural, emerging vegetation, with grass used to provide initial and long-term erosion resistance. If natural vegetation, usually grass, is unfeasible, concrete lining is used. Also, flexible linings comprised of rock riprap asphalt or articulating concrete grids can be used for preventing erosion. Allowable velocities and permissible depths of flow are provided in the drainage volume of the design manual, along with various adaptations of Manning's Equation suitable for evaluating channel capacity.

1.

Divide the watershed into appropriate subareas to correspond with homogeneous land use conditions and the placement of drainage facilities such as inlets, reservoirs, and open channels.

2.

Collect and analyze watershed data.

3.

Establish design storm conditions appropriate for the procedure selected.

4.

Calculate the peak runoff rate or determine the time distribution of rainfall excess. No further calculations are generally required if only the peak runoff rate is desired.

1.

5.

Develop a unit hydrograph for the watershed, if a runoff hydrograph is desired and the procedure selected uses a unit hydrograph.

3. 4.

6.

Develop the direct runoff hydrograph, using the unit hydrograph and rainfall excess determined above, as appropriate.

5.

as

OPEN CHANNEL HYDRAULICS

Open channels can be generally classified as those which occur naturally and those which are manmade or improved natural channels. The later, called artificial channels, include the following types in use on most roadway project:

2.

6.

Part 1 300-15

Right-of-way ditches which usually acts as an overland flow interceptor ditch collecting water before it reaches the roadway. Roadside or roadway ditch and (sometime called the “borrow ditch”) Median ditches on divided highway. Outfall ditches for connecting and carrying flows from ditch types 1, 2 and 3, a short distance to a natural outlet or to another, larger conveyance channel. Lateral ditches are a larger size channel, usually used for continuing upstream flows past the project area. Canals are large size conveyance channels.

ROADWAY DESIGN MANUAL – Roads and Bridges Each of these channel types are artificial systems designed to provide specific drainage capacities. The right-of-way ditch functions as a type of relief ditch, handling drainage needs other than those for the roadway and thus freeing roadside ditches from carrying anything except roadway runoff. Right-of-way ditches can also act as interceptor ditches to provide a method for intercepting offsite flows or subsurface groundwater flows above cut slopes, thereby controlling slope erosion. In general, roadside or median ditches are relatively shallow trapezoidal channels or swales (which are shallow triangular channels). Both types are designed to handle local surface runoff from roadway surfaces, or to lower water table elevations by intercepting groundwater. In some cases, they may also handle other than project drainage. Outfall ditches or canals are designed in most cases as receptors of runoff from numerous secondary drainage facilities, such as side ditches or storm drains. The use of a roadside ditch as an outfall ditch is not recommended, since its probable depth and size could create a potential hazard. 311.05

BLHR and the BHRS shall be prepared for the projects listed below:

2. 3.

Bridges and large culverts (culverts larger than 1800 mm dia pipes or 1200 mm x 1200m box culverts) on new alignments Bridge and large culvert replacements on existing alignments For other bridge and large culvert projects involving actions within the Base Flood Plain (work within the 100 yr. Flood elevation) e.g., bridge widening and large culvert extensions.

Bridge Location and Hydraulics Report

A. Documentation: Documentation shall be provided in detail commensurate with the complexity of the project. Documentation shall be sufficient enough so that an independent engineer with expertise in bridge hydraulics, but not involved with the design, can fully interpret, follow and understand the logic, methods, computations, analysis and considerations used to develop the final design. Documentation for bridge and large culvert designs shall include as a minimum the following: 1. Hydrologic analysis including sources of data and methodology. 2. Alternative analysis or evaluation of structure sizes (length and vertical height/clearance). This evaluation shall be done consistent with Department criteria for bridge hydraulic design and shall include consideration of: a. cost b. design standards c. structure hydraulic performance, including backwater, velocity and scour d. Impacts of the structure on adjacent property e. environmental impacts

BRIDGE HYDRAULICS

Bridge hydraulic designs shall be documented in the Bridge Location and Hydraulics Report (BLHR). Design information shall be summarised on the Bridge Hydraulics Recommendations Sheet (BHRS). The format for the BHRS is provided in Section 3.11.

1.

311.05.01

3. The alternative analysis shall include the reasons for selecting the recommended structure and a clear explanation as to why it is the most economical structure for the site in question. As a minimum, the following structure sizes shall be evaluated: a. The minimum structure size required to meet hydraulic standards for vertical and horizontal clearance, scour and backwater. b. Existing structure size if applicable. c. The recommended structure size if different from (a) or (b). 4. Design recommendations for recommendations shall include:

Part 1 300-16

bridges

ROADWAY DESIGN MANUAL – Roads and Bridges a. Bridge length, and justification for the length, including locations (stations) of abutments b. Channel excavation requirements c. Minimum vertical clearance d. Minimum horizontal clearance e. Abutment type and orientation f. Pier orientation g. Scour depths for the design flood, 100year flood and maximum probable flood (usually the 500-year flood). h. Scour protection requirements for abutments, piers and channel i. Deck drainage

the subsections identified below. Rather than a formal item by item approach, a narrative description of the site and the hydraulics recommendations is suggested. Preliminary Information A. General Site Location 1. Highway Description a. Type (expressway, main, secondary, rural, urban, etc.) b. Lanes (two, four, divided, limited across, etc.) c. Importance (main access between towns and borders, military route, alternate routes available, etc.)

5. Documentation of large culvert hydraulic designs shall include hydraulic calculations and recommendations for the following: a. Culvert Size, and justification for the size, barrel length and location b. Peak water surface profiles and crosssection velocity profiles for the design flood, the 100 yr flood and the maximum probable flood for a distance 150 meters upstream, through the culvert to a distance 150 metres downstream. c. Upstream and downstream invert elevations. d. Endwall type for entrance and outlet, including the need for an improved inlet. e. Skew f. Inlet end and outlet end scour protection requirements 6. Final project plans shall show the peak stages, peak discharges, peak velocities, and peak scour predictions for the design flood, the 100 year flood and the maximum probable flood that can be expected to flow through the structure.

2. Topography of site and basin 3. Location: small scale map with site located B. Potential Site Problems 1. Land Use Department)

(obtain

from

responsible

a. Encroachment on the flood plain b. Recreational use c. Domestic water supply d. Security area 2. Channel Stability a. b. c. d. e.

Bank stability Bends and meanders Potential for natural change of channel Aggradation or degradation of bottom Scour history

3. Potential Water Stages

B. Report Outline: An outline of items that should typically be considered in the preparation of a BLHR is given below. Non-applicable items should be so indicated rather than omitted without comment. Additional information may be appropriate at unusual sites. The BLHLR should be divided into two basic sections: Preliminary Information and Design Data. These sections are then broken down into Part 1 300-17

a. Flood history (dates; stages; source of information; extent of flooding; approximate frequency; damage to structure, embankment or highway) b. Potential backwater from other streams or rivers c. Reservoirs of flood control projects (Department and status) d. Tidally affected (mean high and low water)

ROADWAY DESIGN MANUAL – Roads and Bridges e. Other controls, if any f. Normal high and mean high water stages 4. Clearances (horizontal and vertical) a. Drift at flood stage (not necessarily at peak backwater stage) b. Navigation at mean high water or normal high water stage

7. Determination of design discharge and development of discharge-frequency curve 8. Determination of design flood stage and development of stage-storage-frequency curve D. Hydraulic Analysis 1. Bridges a. Determination of permissible upstream water surface b. With bridge length set to minimum criteria or environmental controls, determination of backwater c. Adjustment of (b) if required to satisfy (a) d. Check of conveyance for 100-year flood and maximumbable flood; adjustment of bridge length if required e. Evaluation of scour potential f. Evaluation of need for channel changes g. Evaluation of need for bank protection including limits of protection, type, materials, and specifications h. Evaluation of need for spur dikes and other training devices i. Evaluation of effects of construction and temporary activities j. Evaluation of effect on downstream structures and properties

Final Design Data A. Inventory of Existing Crossing(s)

1. Location in relation to crossing(s) 2. Determination of drainage area (when significantly different) 3. Physical data on structure(s) (size, type, spans, foundation type, low member, available waterway area) 4. Flood history 5. Evaluation of hydraulic adequacy of structure(s) (Note: This data should be obtained not only for the site under consideration, but upstream and downstream crossings as well) B. Selection of Design Flood 1. Importance to highway system 2. Importance to life and property 3. Conveyance of design, 100-year and maximum probable flood (under or over/under the highway)

2. Large Culverts (any cross-drain culvert larger than 1800 mm dia pipe, or 1200mm x 1200 mm box culverts)

C. Hydrologic Analysis 1. Site review (extremely important) 2. Interview with persons providing flood history data 3. Review of available flood records (Department, newspapers) 4. Review of available stream gages in vicinity 5. Definition of drainage area above site 6. Evaluation of potential watershed basin changes (20-year minimum) a. Urbanization b. Channelization c. Water management practices

Part 1 300-18

a. Determination of allowable headwater (AHW) and design storm tailwater elevations b. Selection of trial culvert size c. Evaluation of culvert for abrasion, corrosion, debris, scour, suitability for improved entrance, etc. d. Design of inlet and outlet scour protection, if necessary e. Check of conveyance of 100-year flood and max. probable flood f. Evaluation of effect on stream stability. g. Evaluation of effect on fish and wildlife, if applicable h. Evaluation of effect of channel change i. Evaluation of effect on downstream properties and structures

ROADWAY DESIGN MANUAL – Roads and Bridges E. Additional Survey Data of Proposed Site 1. Data sufficient to prepare a contour map (intervals at 30 cm or 60 cm depending on scale); required distance upstream and downstream will vary with site 2. In lieu of (1), a minimum of three cross sections will suffice for some cases (upstream, at, and downstream of site) 3. Vegetation, estimated bed load, bottom soil material and soil properties, and other general site parameters F. Departmental Coordination 1. Contact Departments involved and identify what other projects may be affected by the culvert/bridge 2. Investigate possibility or necessity for a cooperative project It is also suggested that a checklist of required items for each site be prepared and given to the survey crew to ensure complete data will be obtained with a minimum of supplemental or unnecessary effort. 311.05.02

Bridge Hydraulics Recommendations Sheet (BHRS)

The BLHR is a full size drawing, to be included with the BLHR. It is divided into several information blocks, which must be as completely filled out as is appropriate for the design and location. The BHRS must always include the Project Number and the Bridge Number as per the drainage map in the title box. The information requested for existing bridge or large culverts near the site includes foundations, overall length, span length, type of construction, area of opening at high water, roadway width, and the low member elevation. The area of opening at high water generally refers to the flow area available through the existing structure below the water surface determined for a design storm frequency.

design flood, the base (or 100-year) flood, and either the overtopping or maximum probable flood, whichever occurs first. The overtopping flood is the one in which flow crosses the highway, or spills into another watershed or through a relief structure. The max. probable flood is normally a 500-year event. Flood data includes stage elevation, discharge, average velocity (on larger crossings a velocity profile across key cross-section is usually needed) and exceedance probability. Water surface elevations are classified as normal high water for non-tidal areas and as mean low and mean high water for tide-influenced areas. Normal high water is defined as the 2-year event; mean low water and mean high water data can be obtained from the admiralty charts. Hydraulic recommendations should include the beginning and ending bridge stations, data on the channel section (including any excavation), navigation and drift clearances, scour prediction, slope protection, and deck drainage. Space should be provided for a small scale location map outlining the drainage area. A plan view of the existing and proposed bridge area must also be included. The scale should adequately depict the area adjacent to the structure, including existing and proposed contours. Drainage areas for very flat sites warrant careful delineation since only one or two contours may occur. For a bridge, a profile of the channel section should be shown; for a large culvert, the culvert centreline should be profiled. The profile should show channel work and bridge end treatment. If necessary for clarity, bridge ends should be drawn at a larger scale. The assumed configuration, deck drainage, and scour recommendations need to be approved by the Municipality before plans are completed. This review provides an opportunity to evaluate the impact of substantial changes on the hydraulic design conditions.

The BHRS hydraulic design data section should include water surface elevations and several categories of flood data for various events, including the maximum event of record, the Part 1 300-19


STORMWATER MANAGEMENT USING RETENTION/DETENTION DESIGN

In general, retention refers to stormwater storage without access to a positive outlet, while detention facilities offer temporary storage accompanied by controlled release of the stored water. Wet detention typically has a pool of water below the outlet elevation; dry detention is typically placed with the basin bottom above the seasonal high water table. Retention and detention can be used separately or together in storage basins as site conditions and management objectives require. Historically, "detention" basins are used only when such use reduced the outfall size (by reducing the peak discharge) enough to justify the cost. An additional benefit is that they can also be effective in improving stormwater quality. The drainage volume of the design manual provides general design criteria for retention/detention basins as well as procedures for performing preliminary sizing and final reservoir routing calculations. The Storage Indication Method is presented as an acceptable method for detention calculations. Exfiltration calculations may be required for certain retention systems for estimations of percolated discharge rates. Land-locked drainage areas will require retention storage areas designed to meet special considerations. The collection of field and published data for the planning and location of retention/detention facilities should be coordinated so that it can be accomplished concurrently with other aspects of a particular project. A general discussion of data collection procedures is presented in Section 311.02.03. A key element to proper planning of retention/detention facilities is the selection of potential sites that will provide control of both flooding and stormwater quality. Other important considerations include: • •

Runoff quality requirements Stormwater management master plan

• • • • • • • • • • •

Conveyance of drainage to the site Availability of land Suitability of site for water storage Availability of suitable outlet point Adjacent land use Roadway control elevations Soil infiltration capability Water table fluctuations Outfall high water elevations Type of facilities proposed Safety and maintenance requirements

Planning for retention/detention facilities should be co-ordinated with the evaluation of borrow requirements for the project. To the maximum extent possible, excavation from construction of the retention/detention basins should be used as fill material. If borrow material is required for basin embankments, it should be obtained within the project limits, if possible. The objective of drainage design is to provide the necessary roadway drainage facilities which allows the public to use the roadway during times of significant runoff and in a manner that minimizes the potential for adverse effects on adjacent property and existing patterns. The effect of the roadway on the existing drainage pattern, the potential flood hazards, as well as the effect of floods on the roadway are to be assessed in the design process. The engineer shall perform a drainage study in accordance with current design methodology, requirements and criteria in the drainage volume of the design manual. The criteria should identify such items as the hydrology method to be used, the design storm frequency to be accommodated, the allowable spread of water on the pavement to be tolerated at the specified storm frequency and any other pertinent hydraulic criteria which is a design control for the project. Applicability of existing Master Drainage Plans will be discussed. The purpose of the drainage study is to identify potential drainage problems for the proposed improvement, to recommend solutions, and to establish initial pipe and channel sizings and alignments consistent with the improvement concept. The major drainage features shall be

Part 1 300-20

ROADWAY DESIGN MANUAL – Roads and Bridges displayed on the roadway geometric plans in both plan and profile. Basic hydrologic conditions should be fully quantified and discussed. Analysis of preconstruction hydrologic conditions should be performed in order to evaluate hydraulics (capacity, velocity, flood over-topping elevations etc.) of any existing structures and the impacts of alternatives considered. The engineer shall research and evaluate potential future development (20 year planning horizon) within the watershed which may have an impact on future drainage flows and ultimately the performance of existing or proposed hydraulic structures. The engineer shall carefully document and photograph all existing drainage problems, carefully evaluate recommended solutions and assure existing conditions are not impacted by roadway improvements. The engineer shall document drainage problems, design approaches, solutions, and initial hydraulic structures requirements in a separate Initial Drainage Study which will be included in the Appendix. A summary will be presented in the DCR.

312

The Geotechnical Report will assemble the results of the subsurface exploration program, analyze, and make geotechnical engineering recommendations using the field boring and lab test data. This will be presented in an engineering report, prepared by the engineer for the project and included in the Appendix. The results will be summarized in the DCR. The Report information: • • • • • •

• • • •

SUBSURFACE INVESTIGATIONS

is

to

contain

the

following

Summary of previous geotechnical investigations description of the program undertaken to identify geotechnical and subsurface elements which affect project design results of surface visual observations groundwater data a summary of the information obtained from and the location diagram of the soil borings the general description of the subsurface geologic strata obtained from the soil borings, including any areas of unacceptable soil conditions particle size analysis and potential for scour results of any material testing analysis and recommendations for embankment construction including settlement and surcharging an analysis and preliminary recommendations for pavement structural section and foundations.

Once the project location, horizontal and vertical alignment and structure requirements have been generally defined, the engineer will formulate subsurface exploration and testing program. The objective of the exploration program, is to provide, specific subsurface information along successive design sections or reaches of the project. The data will allow some basic judgments to be made, i.e., the most suitable type(s) of foundations for structures and recommended pavement designs to be developed during the design phase.

313

BRIDGE TYPE SELECTION

In the case of either the structure borings or roadway borings, the geotechnical program will serve to reveal the type, severity and extent of geotechnical design problems.

When performing the concept studies following shall be considered as a minimum:

Selection of the most suitable type of structure involves investigating alternate superstructure and foundation types including variation of span length, structure depth and number of girders to determine the best bridge type and arrangement for a particular site. This is an iterative phase where assumptions must be made and later verified or modified during the process. Detailed design should not be performed unless it is necessary to confirm the adequacy of a concept.

• • •

Part 1 300-21

Cost Constructability Maintenance

the

ROADWAY DESIGN MANUAL – Roads and Bridges •

•

Aesthetics

The existing waterway opening, vertical and horizontal clearances. The need for adding approach slabs. The adequacy of existing bridge rail.

Sketches should be made of the various alternatives investigated and included in the report.

• •

Both the vertical and horizontal clearances should be checked to ensure that adequate clearances are provided. Inadequate vertical clearance will necessitate a change in either profile grade or superstructure depth while inadequate horizontal clearance may necessitate a change in span length.

When the above items have been investigated, preliminary design can proceed by studying alternatives. Possible alternatives include: widening to one side, widening symmetrically on both sides or replacing the bridge with a new structure. Approximate costs based on preliminary quantities and unit costs associated with each solution will be required.

The geotechnical aspects of the site should be considered since the foundation type and associated cost may influence the type of bridge selected. An initial (stage one) subsurface exploration and testing program will be performed in parallel as described in Part 1, Section 312, Subsurface Investigations, and will be used to determine foundation type and costs. Traffic requirements must be investigated including any detours or phasing requirements. These requirements will be addressed in the discussion detailed in Part 1, Section 320, Construction Staging. 313.01

BRIDGES OVER WATERWAYS

For waterway crossings, coordination with the project drainage requirements will be necessary. The designer should obtain the Initial Drainage Report and thoroughly review the contents before starting the analysis of alternatives. For navigable crossings, the channel width, vertical clearance, pier protection and navigational aids should be investigated and discussed. 313.02

WIDENINGS/REHABILITATION

On projects involving widenings, in addition to the requirements for new bridges, the following items should be investigated: • • • • •

The existing structure should be checked for structural adequacy. The condition of the existing deck joints. The condition of the existing bearings. The condition of existing diaphragms on steel girder bridges. The existing foundations.

313.03

BRIDGE SELECTION REPORT

The preparation of the Bridge Selection Report is the final activity in the preliminary design phase. This activity involves incorporating the contents of the Initial Drainage Study, and the Geotechnical Report to produce a final Bridge Selection Report and develop the preliminary plans for the selected alternative. The preliminary plans consist of the General Plan and General Notes and Quantities Sheets. The preliminary plans are not considered complete until the drainage report and geotechnical foundation recommendation is received and incorporated in the plans. After fully considering the above factors to determine the proper structure type, the engineer will discuss the architectural features with the appropriate Municipality Departments. For large or controversial projects, approval by the Executive Council or higher authority will be required. These may be individual or joint discussions as dictated by the size, location, complexity, and sociological, economical, ecological and environmental demands of the project. Through these discussions a structure with architectural features that are compatible with structural, safety and site requirements can be developed. The completed Bridge Selection Report shall include a general plan of the bridge. This reduced plan reflects the bridge geometrics, architectural theme, the bridge substructure and the type of foundations. A complete discussion of the cost

Part 1 300-22

ROADWAY DESIGN MANUAL – Roads and Bridges and feasibility of alternative designs must be included. This is especially important for unusual and major structures. The Bridge Selection Report will be included as an Appendix to the DCR. The results of bridge type selection process will be summarized in the DCR. The factors that led to the selection of the preferred alternative will be thoroughly discussed. The proposed structures should be described and address: • • • • • •

Foundation Type Substructure Superstructure Architectural Features Vertical and Horizontal Clearance Other Key Factors

UTILITY IMPACT ANALYSIS

Utility impacts are a key project issue, especially within existing transportation corridors. Data collection and coordination with the various agencies/departments is discussed in Part 1, Section 200, Design Concept Development. The second phase of work includes analysis of the existing and proposed utilities with respect to each alternative in order to permit estimation of costs and evaluation within the alternatives matrix. Utility corridors including proposed Service Reservations should be identified and indicated on the typical sections and roadway plans included in the DCR. For urban projects, the location of service reservations will affect the roadway geometrics including parking areas, green areas and the proposed pavement surfacing. The DCR will include a through discussion of the utility impacts and a tabulation of the existing utility inventory as follows: • • • •

Item Number Owner Description Station

Location Status Remarks

The DCR will summarize the impacts for each major utility (water, sewer, telephone, irrigation, electrical). The responsibility for design and construction of the facilities will be addressed. Schematic plans showing the major existing and proposed utilities should be prepared and included in the drawings section. Recommendations will be given for general utility relocation schemes and for resolution of specific utility conflicts. Associated utility costs will be included in the preliminary cost estimate. For larger projects a separate Utility Report should be prepared and included as an Appendix to the DCR.

The General Plan shall be included in the Drawings (A3 size) that will accompany the DCR.

314

• • •

315

SOCIOECONOMIC ANALYSIS

An analysis and discussion of the socioeconomicdata per the requirements described in Part 1, Section 202, Environmental Factors Influencing Design, shall be included in the DCR. Each of the topics covered in Part 1, Section 202, Environmental Factors Influencing Design shall be included or, if not relevant, it should be so stated including the reason why it is not relevant. For any of the topics which are not relevant, prior approval from the Municipality is required to exclude the issue from the DCR. The required information as to the reasons why the topics are not relevant shall be summarized in a concise Technical Memorandum accompanied by supporting documentation as necessary. The Municipality shall make a determination as to the relevance of the topic based on this information. The Technical Memorandum and supporting documentation is to be included as a separate appendix in the DCR.

316

AGRICULTURE IMPACT

Agricultural resources are important to man’s survival and therefore must be preserved to the greatest extent possible. The Consultant shall identify the potential impact that the proposed project alternatives may have on these resources within the study area. Primarily, this involves

Part 1 300-23

ROADWAY DESIGN MANUAL – Roads and Bridges determining whether or not the project will directly impact (i.e. irreversibly commit ) land that is presently used for agricultural purposes. In the description of impact, the Consultant shall identify whether the land is actively farmed or fallow as well as the types if crops that would be affected. Impacts will be quantified in hectares. Indirect impacts will also be identified and described. These may include, but are not limited to, the potential description of the existing irrigation system or pollution of nearby agricultural lands from untreated stormwater runoff. Impacts associated with each project alternative will be compared and the alternative with least agricultural impact shall be identified if such an alternative exists.

317

PUBLIC FEEDBACK

Public involvement is an important aspect in the overall success of a project. At the onset of the project, the consultant shall develop a Public Involvement Plan that will establish the approach to be used to coordinate project planning and details with the public. In addition to keeping the public informed of the project, the plan will also provide the public with the opportunity to comment at various stages of project development. By soliciting and actively considering public input, the Consultant is more likely to produce a design that is economically feasible and acceptable to the public. This section of the DCR should briefly describe the elements of the Public Information Plan, including the location and scheduling of public information meetings, workshops, consensus building sessions or any other forums aimed at soliciting public input. A summary of the primary issues raised by the public should be presented along with a discussion of how these issues have been addressed during the development of the project, and whether or not consensus has been reached. A file should be maintained as backup for each public meeting that contains a list of participants and the issues raised.

318

SIGNING AND PAVEMENT MARKINGS

Signing Concept plans will be developed to show the major guide signs required for the proposed facility in accordance with the MUTCD and criteria included in Part 2, Section 900, Traffic Engineering. It may be necessary to include signing outside of the project limits. New signs or modifications required to existing signs shall be clearly identified. The signing requirements shall be displayed on a reduced scale version of the project geometrics sufficient to show the required detail. Proposed guide signs should be illustrated graphically with leaders pointing to the sign location. Signing requirements associated with the construction staging/detour scheme should also be discussed. The signing and lighting concept plans will be included in the drawings section of the DCR.

319

LIGHTING CONCEPTS

This section should begin with a discussion of the design criteria that governs the location of lighting, the type of lighting relevant to the roadway classification or route and the method of illumination analysis. Applicability or conformance to existing Master Lighting Plans must be considered. Alternative types of lighting such as high mast at major interchanges should also be addressed. The typical spacing between light sources, and the compatibility with adjacent or intersecting lighting system will be shown and illustrated on schematic plans.

320

CONSTRUCTION STAGING

Maintenance of traffic during construction can have a significant affect on the surrounding traffic system, in terms of public convenience, design, cost and the duration of construction. The DCR shall include a discussion as to how construction of the project will be staged including:

Part 1 300-24

ROADWAY DESIGN MANUAL – Roads and Bridges • • • •

• • • • •

Number of Stages Erection of Falsework Anticipated Detours Duration of each Stage

The final design plans will generally be prepared in conformance with staging described in the DCR.

321

COST ESTIMATE

The DCR preliminary cost estimate must be as realistic and accurate as possible. The degree of effort and detail for each project is expected to vary depending upon the complexity and sensitivity of the project-related issues. The preliminary cost estimate should be prepared using the “Preliminary Project Cost Estimate” form (Figure 300.02) to summarize the individual bills. This is intended to standardize the format and type of items that need to be considered in the project consistent with the General Specifications. Similar forms must be developed for each bill section to back-up the summary, including the estimated quantities and unit prices. It is important that all known items of work be identified and estimated. In some instances, not all of the items can be identified at this stage and an appropriate contingency factor should be applied to reflect possible increases such as modification of the project limits or adding decorative features.

322

324

• • • • • • • •

CONCLUSIONS/ RECOMMENDATIONS

APPENDIX

This section will be used for appending Technical Memorandums and the complete detailed studies or reports including: • •

DRAWINGS

The drawings prepared to illustrate and define the design concept should be presented in A3 format as Volume II of the written report which is bound separately in A4 format. The drawings should include the following:

This section will include conclusions, recommendations, and their associated costs. The name and title of the Project Engineer responsible for the preparation of the DCR as well as the Abu Dhabi Municipality’s Engineer who served as the Municipality Representative shall also be indicated.

323

Initial Drainage Study Geotechnical Report Bridge Selection Report Utilities Report Traffic Analysis Report

Fact Sheet-Design Exceptions Parking Study Part 1 300-25

Typical Sections Alternatives Bridge General Plans Roadway Plan/Profile Signing and Lighting Concept Plans Architectural Renderings Construction Staging Schematics Other project specific plans as required

ROADWAY DESIGN MANUAL – Roads and Bridges MUNICIPALITY OF ABU DHABI PROJECT NAME AND ROUTE NO.___________________ PROJECT NUMBER_________________

PRELIMINARY PROJECT COST ESTIMATE SUMMARY OF BILLS OF QUANTITIES

BILL NO.

BILL DESCRIPTION

AMOUNT IN FIGURES DH

I

GENERAL

II

EARTHWORKS

III

SUBBASE AND BASE COURSES

IV

ASPHALT WORKS

V

CONCRETE WORKS

VI

SURFACE DRAINAGE SYSTEM

VII

WATER WORKS

VIII

PRESTRESSED CONCRETE WORKS

IX

TRAFFIC MARKINGS AND SIGNS

X

SITE LABORATORY

XI

CONCRETE PILE FOUNDATIONS

XII

METAL WORKS

XIII

POST-TENSIONED CONCRETE WORKS

XIV

EXPANSION AND FIXED JOINTS

XV

IRRIGATION WORKS

XVI

LIGHTING AND ELECTRICAL DISTRIBUTION WORKS

XVII

TRAFFIC CONTROL SYSTEM

XVIII

DAILY WORKS SCHEDULE

XIX

TELEPHONE WORKS

XX

SEWERAGE WORKS

XXI

STREET FURNITURE

XXII

PARKING STRUCTURE

XXV

LANDSCAPING TOTAL ESTIMATED COST Figure 300.02 Cost Estimate Worksheet

Part 1 300-26

Fs

ROADWAY DESIGN MANUAL – Roads and Bridges rails, bridge columns, retaining walls, sound walls, cut slopes, and median barriers.

PART 2 ROADWAY DESIGN SECTION 100 GENERAL DESIGN CRITERIA 101

DESIGN SPEED

The cost to correct such restrictions may not be justified. Technically, this will result in a reduction in the effective design speed at the location in question. Such technical reductions should be discussed and carefully considered before accepted.

Design speed establishes specific minimum roadway design elements. These design elements include vertical and horizontal alignment, and sight distance. Design speed relates indirectly to other elements such as pavement and shoulder width, and horizontal clearance.

Design speed may be lowered, especially in densely developed urban areas. The design speed for special projects will be established by the Road Section. Maximum design speeds, as related to roadway classifications, are shown in Table 100.01.

Design speed is influenced by terrain, economic considerations, environmental factors, type and volume of traffic, roadway functional classification, and adjacent land use (rural or urban).

Table 100.01

Drivers expect consistent design speeds for adjacent roadways or roadways with similar characteristics. A driver in a mountainous area would expect to travel more slowly than a driver crossing the open desert. Further, the driver crossing the open desert expects the travel speed to be similar for a divided road or a two-lane roadway. Normally, the design speed difference between adjacent segments should not exceed 10 kph. A roadway carrying a large traffic volume may justify a higher design speed than a less important facility in similar topography, particularly where the savings in vehicle operation and other costs are sufficient to offset the increased cost of right of way and construction.. However, a lower design speed should not be assumed for a secondary road where the topography is such that drivers are likely to travel at high speeds. Subject to the above considerations, as high a design speed as practical should be used. The design speed for any section of roadway should be a constant value. However, during design, situations may arise in which engineering, economic, environmental, or other considerations make it impractical to provide the minimum elements established by the design speed. Examples include partial or brief horizontal sight distance restrictions, like those imposed by bridge

Roadway Classification RURAL Freeway

Design Speed Terrain Desirable Type (kph)

Min. (kph)

Flat 140 120 Rolling 120 100 Mountainous 100 80 Expressway Flat 140 120 Rolling 120 100 Mountainous 100 80 Major Collector Flat 100 80 Mountainous 80 60 Minor Collector Flat 90 80 Rolling 80 60 Mountainous 60 40 Local Access Flat 90 80 Rolling 80 60 Mountainous 60 40 URBAN Freeway 120 100 Expressway 120 100 Arterial (Main Rd) Outlying 100 80 Low Interruption 90 60 High Interruption 60 40 Frontage Road 60 50 Sector Road 50 40 DIRECTIONAL RAMPS 80 60 The maximum design speed varies by area on Abu Dhabi Island therefore, refer to Figure 100.01 for the posted speeds on the Island. Posted speeds are considered to be approximately 85% of design speed.

Part 2 100-1


Figure 100.01 Posted Speeds On Abu Dhabi Island Part 2 100-2


Within a project, one design designation should be used except when:

DESIGN VEHICLES

For primary roadway projects, the design vehicle will be a WB-12 intermediate semi trailer combination. For secondary and local roads, the design vehicle will be a single unit bus. The design vehicles are as defined in a “A Policy on Geometric Design of Highways and Streets”, AASHTO, 1994. Refer to Section 405 for additional information on design vehicles.

103

(a) The design hourly traffic warrants a change in the number of lanes, or (b) A decided change in topography dictates a change in design speed. The design designation should appear on the typical cross section for all new roadway construction projects.

DESIGN TRAFFIC 104

103.01

ROADWAY CAPACITY

DESIGN PERIOD 104.01

Geometric design of new facilities should be based on estimated traffic 20 years after completion of construction unless otherwise directed by the Road Section. Safety, resurfacing, restoration, rehabilitation, and operational improvement projects should be designed using current traffic volumes with consideration for future growth. 103.02

Design capacity is the maximum volume of traffic for which a projected roadway can provide a selected level of service. Design capacity varies with a number of factors, including: (a) (b) (c) (d)

RELATION TO DESIGN

The design designation is a simple, concise expression of the basic factors controlling the design of a given roadway. Following is an example of this expression: ADT (2000) = 9800 D = 60% ADT (2020) = 20,000 T = 12% DHV = 3000 V = 110 kph,

(e) (f) (g) (h) (i)

(j)

where: ADT (2000) = The average daily traffic, in number of vehicles, for the construction year. ADT (2020) = The average daily traffic for the future year used as a target in design. DHV = The two-way design hourly volume, vehicles. D = The percentage of the DHV in the direction of heavier flow. T = The character of the traffic. This is expressed by the truck increment (T) as a percent of the DHV (excluding recreational vehicles). V = Design speed in kph.

DESIGN CAPACITIES

(k)

Level of service selected. Width and number of lanes. Weaving sections. Presence or absence of, and width of, shoulders. Grades. Horizontal alignment. Operating speed. Lateral clearance. Side friction generated by parking, drive ways, intersections, and interchanges. Volumes of trucks, buses, recreational vehicles, bicycles and pedestrians. Percentage of trucks, buses, and recreational vehicles. Spacing and timing of traffic signals.

Design capacity is based on the factors above, design year traffic and operation at a specified level of service (LOS). Broadly defined, in terms of traffic flow, LOS A is associated with free flow traffic; LOS B indicates reasonable free flow; LOS C is stable operation; LOS D is lower range of stable flow; LOS E is unstable flow; and LOS F indicates forced flow. Design levels of service for various conditions are shown in Table 100.02. The highest feasible LOS should be selected and used for design, except

Part 2 100-3

ROADWAY DESIGN MANUAL – Roads and Bridges where unreasonable costs or environmental constraints would dictate a lower LOS. Level terrain is defined as a roadway on which trucks can maintain speeds that approach or are equal to those of passenger cars. Rolling terrain is defined as a roadway on which trucks substantially reduce their speed below passenger cars on some sections. Mountainous terrain is defined as a roadway where trucks operate at crawls speeds for long distances or frequent intervals. Table 100.02 Relation of Conditions to Design Levels of Service Conditions RURAL Freeway

Expressway

Design Levels of Service Flat Rolling Mountainous Flat Rolling Mountainous

B B C B B C

Flat Rolling Mountainous

B B C

Flat Rolling Mountainous Flat Rolling Mountainous

C C D D D D

Major Collector

URBAN Freeway Expressway Arterial (Main Rd) Frontage Road Sector Road DIRECTIONAL RAMPS

Level of Service Urban Rural

C-E C-D

Traffic Volume (Average Vehicles) Per Lane Per Hour 1400-2000 1000-1200

The following sections deal with the general capacity calculations for various roadways. Since these calculation methods are lengthy and beyond the scope of this document, the reader is referred to the Highway Capacity Manual (HCM), 1994. 104.01.01 Multi-lane Rural Roadway The general equation for service volume of all multi-lane roadways is given by: SV = 2000 N (v/c) T W where: SV = Service volume (one direction) for a given level of service N = Number of lanes in each direction v/c = Service volume to capacity ratio T = Adjustment factor for trucks on grades W = Adjustment for width and lateral clearance (See HCM Section 100.04.02)

Minor Collector

Local Access

For an approximation of the number of lanes required on a multi-lane freeway or expressway, use the following design year peak hour traffic volumes at the specified level of service:

104.01.02 Two Lane Roadways Service volumes and capacities for two lane roadways are always both directions without regard to the distribution of volume by direction.

C C C-D D D B-C

As an alternative to level of service D, consideration should be given to pairs of one-way roads or alternative bypass routes to improve the LOS.

The general equation is given by: SV = 2000 (v/c) T W where: SV = Service volume in vehicles per hour (total both directions) v/c = Service volume to capacity ratio T = Adjustment factor for trucks on grades W = Adjustment for width and lateral clearance (See HCM Section 100.04.02)

Part 2 100-4


Expressways

Expressways are analyzed using a series of nomographs covering a range of average roadway speeds. The charts are based on 3.65 m lanes, full width shoulders, and adequate clearances. (See HCM Section 100.04.02) 104.01.04

Expressway Ramps and Weaving Sections

Capacities of urban expressways are influenced by entrance and exit volumes, weave distance, and the geometric layout. All of these factors should be considered in the capacity analysis. (See HCM Section 100.04.02) 104.01.05

Intersection Capacity

Intersections capacity generally governs the capacity of the associated roadway. Signal timing, intersection spacing, turning movement all play a critical role in determining the overall capacity. (See HCM Section 100.04.02)

105 105.01

CONTROL OF ACCESS GENERAL

Control of access is achieved by limiting the number and location of roadway access points so that the through traffic capacity or safety of the facility will not be significantly impaired. There are three degrees of access control: Full Access Control - Gives preference to through traffic by providing access only through selected frontage/sector roads and by prohibiting at-grade crossings or direct access from abutting property. Partial Access Control - Still gives preference to through traffic but permits some at-grade crossings and some private driveway connections. Approach Road and Driveway Regulations Without access control, abutting properties are permitted access to the roadway, but the number, location and geometrics are regulated.

Table 100.03 Control of Access by Road Type

Roadway Type

Degree of Access Control

Freeway Expressway Major Collector Main Road Minor Arterial Sector Road Local Road

Full Access Control Full or Partial Access Control Partial Access Control Approach Road and Driveway Regulations

All Roadways will have some degree of access control. The appropriate degree of access control by roadway type is given in Table 100.03. More detailed guidelines for establishing the control of access lines by roadway classification are presented in the following section. 105.02

105.02.01

ACCESS CONTROL DESIGN CRITERIA Primary Roadways

The number of access openings on expressways with access control should be held to a minimum. Parcels which have access to another frontage or sector road as well as expressway frontage are not allowed expressway access. In some instances, parcels fronting only on the expressway may be given access to another sector road by constructing suitable connections if such access can be reasonably provided. With the exception of extensive expressway frontages, access openings are limited to one opening per parcel. Wherever possible, one opening should serve two or more parcels. In the case of a large expressway frontage under one ownership, the feasibility of limiting access to one opening may be prohibitive, or the property may be divided by a natural physical barrier such as a wadi or ridge, making it necessary to provide an additional opening. However, in the latter case, it may be preferable to connect the physically separated portions with a low-cost structure or road rather than permit two openings. Access rights shall be acquired along interchange ramps to their junction with the nearest public road, and shall extend to the end of the ramp taper

Part 2 100-5

ROADWAY DESIGN MANUAL – Roads and Bridges (or at least 50 m beyond the end of the curb return or ramp radius). In remote areas, infrequent access should be accommodated by providing locked gates. This will only be considered for areas that are remote, infrequently used, and have no other access means. Direct access will not be provided if it creates an unsafe condition. Turning movements will be limited to right turns only. Written approval must be granted by the Abu Dhabi Road Section.

105.02.02

Secondary Roadways, ADT > 2500

In general, the number of access openings shall be held to a minimum for any facility. Additional access may be necessary to satisfy a range of design issues/access requirements. The following is a list of issues to consider when providing access points. (1) Emergency vehicles shall have a right to direct roadway access. (2) Private direct roadway access shall be permitted only when the property in question has no other reasonable access to the local road system. (3) If feasible, parcels fronting only on the roadway shall be given access to another public road by constructing suitable connections. (4) Roadway access openings are limited to one per parcel. Exceptions may be considered if they do not affect roadway safety or operation and they are necessary for safe and efficient property use. (5) In certain cases, a natural physical barrier such as a wadi or ridge may divide the parcel. In this case additional access openings may be warranted. However, it may be preferable to connect the physically separated portions of the parcel with a low cost structure or road rather than permit multiple access openings. (6) Wherever possible, one access opening should serve two parcels. (7) When the number of required access openings on one side of a divided roadway exceeds three in 400 m, a frontage/sector road shall be

provided. See Section 105.03, Use of Frontage Roads, for further discussions. (8) Access openings on divided roadways shall not be permitted within 100 m of a median opening unless the access opening is directly opposite the median opening. (9) Access approaches shall be limited to right turns only unless (1) the approach has no signalization potential and allowing left turns would significantly reduce congestion and safety problems at a nearby intersection; or (2) there are no intersections, existing or planned, that allow a U-turn; and (3) left turns can be safety designed without signalization. (10)Access approaches with signalization potential and that require left turn movements must (1) meet the signalization requirements as specified in Part 2, Section 902, Signalization, and (2) shall not interfere with the location, planning, or operation of the general road system and nearby property access. 105.02.03

Secondary Roadways, ADT < 2500

The primary function of these roadways is to provide reasonable and safe access to abutting property. Access needs generally take priority over through traffic as long as roadway safety is not compromised. Control of access is not obtained, but the location, number, and geometry’s of access points must meet the following criteria: (a) The number of access approaches to a parcel shall be controlled by safety and design considerations and shall be separated by at least the stopping sight distance. (b) For safety reasons, frontage roads or parallel service roads are not permitted along twolane roadways because this results in the appearance of a divided roadway. (c) Left turns if safety and design standards are met. (d) In rural areas, approach roads shall be provided as necessary for local access or emergency/rest stops. The maximum spacing

Part 2 100-6

ROADWAY DESIGN MANUAL – Roads and Bridges between approach roads shall be 5 km for these purposes.

(2)

New Alignment. Sector roads generally are not provided on new expressway alignments since the abutting property owners never had legal right of access to the new facility. They may be provided, however, on the basis of considerations mentioned above.

(3)

Existing Alignment. Where an expressway is developed parallel to an existing roadway or local road, all or part of the existing roadway is often retained as a frontage or sector road. Frontage roads must be constructed to serve landlocked remainders or the remainders must be purchased outright if other means of access cannot be provided. The decision whether to provide access or purchase should be based on considerations of cost, right of way impacts, road system continuity and similar factors discussed above.

(e) In urban areas with signalized intersections, the minimum spacing between access points shall be that which is necessary for the safe operation and proper design of intersections as specified in Section 400. 105.03 (1)

USE OF FRONTAGE ROADS

General Policy (a)

(b)

(c)

Frontage roads are provided: • To control access to the urban expressway and main road through lanes, thus increasing safety. • To provide access to sectors. • Maintain continuity of the local road systems. • Provide for non-motorized traffic that might otherwise desire to use the expressway. Typically a frontage road is justified if their construction costs are less than the costs of providing other direct access. Right of way considerations are often the determining factor. Thus, a frontage road would be justified if the investment in construction and extra right of way is less than either the severance damages or the costs of acquiring the affected property. Frontage roads may be required to connect parts of a severed property or to serve a landlocked parcel resulting from right of way acquisition. Direct access to the through lanes is allowable on expressways. However, when the number of access openings on one side of the expressway exceeds three in 500 m, a frontage road should be provided.

105.04

PROTECTION OF ACCESS RIGHTS

Access Control lines/limits shall be shown on the project right-of-way plans. Where possible, the right-of-way line and control of access line should be coincident. For proper control of access, fencing or other approved barriers shall be installed on all controlled access roadways, located on the control or access line where appropriate. 106

DESIGN STANDARD EXCEPTIONS

A design standard exception is a design feature which does not meet the design standards presented in the Roadway Design Manual. Occasionally these design exceptions are justified but it is important that each design exception be documented and approved in writing prior to plan acceptance. The request for approval of design exceptions shall be in the form of a Design Exception Request. This request sheet shall be presented to the Municipality for written approval. The request sheet shall include the following topics:

Part 2 100-7

ROADWAY DESIGN MANUAL – Roads and Bridges • • • • • •

Proposed Project Existing Roadway Proposed Design Exception Additional Cost To Comply Standards Incremental Improvements Supportive Data

Roadway Design Manual Part and Section number(s). B. Describe the proposed design exception or the existing design exception which is proposed to be maintained. If proposed, state whether the design exception is an improvement over the existing condition. Describe proposed improvements that would qualify as safety enhancements over the existing condition, such as: median barrier, guardrail upgrade, flattening slopes, correcting superelevation, eliminating roadside obstructions, etc.

With

A detailed description of the items required in the Design Exception Request sheet is included on the following pages. DESIGN EXCEPTION REQUEST SHEET 1.

PROPOSED PROJECT

C. Provide a thorough brief justification for the design exception. Reasons for granting design exceptions include a combination of excessive cost, right of way impacts and/or environmental impacts. Supportive factors have included low accident frequency, local opposition, and consistency with adjacent roadway segments.

A. Project Description: Briefly describe the project. Note the type of project and/or major elements of work to be done, such as safety or operational improvement, roadway widening, rehabilitation, reconstruction, etc. Provide the geographic project limits and length. B. Proposed Project Total Cost: Include a estimate of the proposed project cost segregated by major elements, including: roadway, structures, right of way, utility relocation, environmental mitigation, etc., as needed. 2.

If relevant, provide a similar brief description of adjacent existing roadway segments, noting existing nonstandard features.

ADDITIONAL COST TO COMPLY WITH STANDARDS Provide a realistic estimate of the additional cost required to meet the design standard for which the proposed exception is requested.

EXISTING ROADWAY A. Existing Roadway Description: Describe the existing roadway features relevant to the proposed design exception. This may include such things as the widths of lanes, shoulders, median, clear zones, roadbed, and structures; horizontal and vertical alignment and clearances; design speed, sight distance, grades, cross slope, superelevation, etc.

3.

4.

5.

INCREMENTAL IMPROVEMENTS Discuss other practical alternatives that are intermediate in scope and cost between the proposed project (requiring this design exception) and the full, standard solution. Provide enough information on costs versus benefits, right of way and environmental impacts, etc., to explain why none of the incremental alternatives are recommended. These alternatives should normally be investigated prior to requesting an exception.

6.

PROPOSED DESIGN EXCEPTION A. State the specific design standard(s) which are not being met and refer to their Part 2 100-8

SUPPORTIVE DATA A. Traffic Data: Provide both ADT’s and DHV (design hourly volumes). Use design year traffic.

ROADWAY DESIGN MANUAL – Roads and Bridges B. Accident Analysis: Safety is of primary importance when considering design exception approval. If relevant, include an accident data analysis to identify prevalent accident types and causes, plus an evaluation of the effect of the requested design exception on accident types and frequencies. C. Attachments:

107 107.01

1.

Provide a location or vicinity map for the project.

2.

Provide plan sheets, cross sections, profiles and/or special details to clearly illustrate the proposed design exception.

3.

Attach pertinent letters, resolutions, meeting minutes, studies, etc., which further develop or clarify the proposed design exception.

GENERAL

Measures such as the following, which are generally of low capital intensity, can considerably enhance a route’s safety and capacity for bicycle traffic:

• • •

107.02

Paved shoulders. Wide outside traffic lane (4.2 m minimum) if no shoulder. Bicycle-safe drainage grates. Adjusting manhole covers to the grade. Maintaining a smooth, clean riding surface.

SPECIAL BICYCLE FACILITIES

At certain locations or in certain corridors, it is appropriate to supplement further the existing highway system by providing specifically designated bikeways (for either exclusive or nonexclusive bicycle use). Rural arterials often are the only direct connection between areas of population and locations to which the public wishes to travel, Schools, parks, and rural housing developments are usually located to be readily accessible by automobile. However, pedestrians and bicycle riders may also wish to travel to the same destination points. When such a situation exists, the designer should consider the effects on the safety and operation of the arterial. A special effort should be made to provide the greatest degree of safety within the economic constraints that must always be considered. 107.03

BICYCLE FACILITIES

The bicycle has become an important element for consideration in the highway design process. Fortunately, most of the mileage needed for bicycle travel is comprised of the street and highway system. While many highway agencies allow bicycles on partially access controlled facilities, most highway agencies do not allow bicycles on fully access controlled facilities.

• •

For further information and guidelines on bicycles, refer to the latest edition of AASHTO, Guide for Development of Bicycle Facilities.

BICYCLE CHARACTERISTICS

To provide for bicycle traffic, it is necessary to become familiar with bicycle dimensions, operating characteristics, and requirements. These factors determine acceptable turning radii, grades, and sight distance. In many instances design features of separate bike facilities are controlled by the adjoining roadway, so that even then consideration of bicycles is an essential element the design of the highway itself. 107.04

BICYCLES AT INTERSECTIONS

When on-street bicycle lanes and/or off-street bicycle paths enter an intersection, the design of the intersection should be modified accordingly. This may mean special sight distance considerations, wider roadways to accommodate on-street lanes, special lane markings to channelize and separate bicycles from right turning vehicles, provisions for left turn bicycle movements, or special traffic signal designs (such as conveniently located push buttons at actuated signals or even separate signal indication for bicyclists).

Part 2 100-9


SECTION 200 GEOMETRIC DESIGN STANDARDS 201 201.01

If providing passing sight distance is not economically feasible, stopping sight distance is the minimum sight distance provided on multilane and 2-lane roads. Stopping sight distance is the minimum provided for interchanges, at-grade intersections and private road connections.

SIGHT DISTANCE GENERAL

Sight distance is the continuous length of roadway ahead visible to the driver. There are three distinct types - passing, stopping, and decision. Passing sight distance is the minimum sight distance required by a driver to safely pass another vehicle. Stopping sight distance is the distance required by a driver, traveling at a given speed, to stop after seeing an object on the road. At certain locations decision sight distance is required to allow drivers extra time for making decisions. 201.02

PASSING SIGHT DISTANCE

Passing sight distance is the minimum sight distance required by a driver to safely pass another vehicle. The sight distance available for passing is the longest distance at which a driver whose eyes are 1070 mm above the pavement can see the top of a 1300 mm high object on the road. Passing must be accomplished without reducing the speed of an oncoming vehicle traveling at the design speed. Table 200.01 lists sight distance standards.

Table 200.01 shows the standards for sight distance related to design speed.

Design Speed

(kph) 30 40 50 60 70 80 90 100 110 120 130

Table 200.01 Sight Distance Standards Minimum Desired Minimum Stopping Stopping Passing Sight (1) Sight (1) Sight Distance Distance Distance (m) (m) (m) 30 45 60 75 95 115 135 160 180 205 235

30 45 65 85 115 140 170 205 250 290 330

220 285 345 410 485 545 605 670 730 795 855

Minimum values shall be avoided in design, higher values are desirable. (1) Increase by 20% on downgrades >3% & >2 km. Values shown are for wet pavements.

Passing sight distance is only considered on 2lane roads and should be provided at frequent intervals. In general, minimum passing sight distance should be provided for 60% of the route length in level terrain, 40-60% in rolling terrain and 20-60% in mountainous terrain. Economics should be weighed against providing passing sight distance or auxiliary passing lanes.

Chapter III of “A Policy on Geometric Design of Highways and Streets,” AASHTO, 1994, contains a thorough discussion of the derivation of stopping sight distance.

201.03

201.04

STOPPING SIGHT DISTANCE

Stopping sight distance is the distance required by a driver, traveling at a given speed, to stop after sighting an object on the road. Stopping sight distance is measured from the driver’s eyes, 1070 mm above the road, to an object 150 mm high on the road.

STOPPING SIGHT DISTANCE AT GRADE CRESTS

Figure 200.02 shows the relationship between vertical curve length, design speed, and algebraic difference in grades. Any one factor can be determined when the other two are known.

Part 2 200-1


Figure 200.01 Stopping Sight Distance on Crest Vertical Curves

Figure 200.02 Stopping Sight Distance on Sag Vertical Curves Part 2 200-2


STOPPING SIGHT DISTANCE AT GRADE SAGS

Stopping sight distance for grade sags is important at night when headlights need to illuminate the road ahead. Figure 200.02, provides the minimum sag vertical curve length which provides headlight sight for a given design speed. Lighting may be considered as an economic option to lengthening the sag curve. 201.06

STOPPING SIGHT DISTANCE ON HORIZONTAL CURVES

Figure 200.03 is used to determine the required clear distance (at a given design speed) from the inside lane centerline to a roadside obstruction. The driver’s eye is assumed 1070 mm above the inside lane centerline (inside with respect to curve) and the object is 150 mm high. With little or no vertical curvature, the sight line is assumed to intercept the obstruction at the midpoint of the sight line, 610 mm above the inside lane centerline. The clear distance (m) is measured from the inside lane center to the obstruction. 201.07

Table 200.02 Decision Sight Distance Design Speed kph 50 60 70 80 90 100 110 120

Decision Sight Distance for Avoidance Maneuver (m) A B C D E 75 95 125 155 185 225 265 305

160 205 250 300 360 415 455 505

145 175 200 230 275 315 335 375

160 205 240 275 320 365 390 415

200 235 275 315 360 405 435 470

A Stop on rural road. B Stop on urban road. C Speed/path/direction change on rural road. D Speed/path/direction change on suburban road. E Speed/path/direction change on urban road. From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets”

DECISION SIGHT DISTANCE

Decision sight distance is the distance required for a driver to detect an unexpected or difficult to perceive information source or hazard in a roadway environment that may be visually cluttered, select an appropriate speed and path, and initiate and complete the required maneuver safely and efficiently. Decision sight distance is used at major decision points such as lane drops, changes in cross section, off-ramp noses to interchanges, branch connections, roadside rests, vista points, and inspection stations. At these locations, sight distance greater than stopping sight distance is desirable to allow drivers time for making decisions The decision sight distances in Table 200.02 provide appropriate decision sight distance rounded for design. Decision sight distance is based on a 1070 mm eye height and a 150 mm object height.

202 202.01

SUPERELEVATION GENERAL

As a vehicle travels a curved section of road it is subjected to centrifugal force which tends to push it towards the outside of the curve. If the surface is flat, the vehicle is held in its curved path by side friction between the tires and pavement. Roadways are superelevated to further counter centrifugal force. Superelevation is the sloping of the roadway surface upward toward the outside of the curve. On a superelevated roadway, centrifugal force is resisted by the vehicle weight component parallel to the superelevated surface and the tire side friction. However, it is impractical to balance centrifugal force by superelevation alone, because for a given curve radius a certain superelevation rate is exactly correct at only one speed. At all other speeds side thrust will either be toward or away from the curve center. This thrust must be offset by side friction.

Part 2 200-3


Figure 200.03 Stopping Sight Distance on Horizontal Curves

If the vehicle is not skidding, all forces are in equilibrium and are governed by the following equation: Centrifugal Factor = e + f = 0.0079V2 = V2 R 127R Where: e = Superelevation rate in m per m = Maximum superelevation rate for emax a given condition f = Side friction factor R = Curve radius in m V = Velocity in kph This equation is used to design superelevated curves for comfortable operation. Standard superelevation rates are designed to keep the portion of centrifugal force countered by tire friction within allowable limits. 202.02

SUPERELEVATION STANDARDS

Maximum superelevation rates for various roadway classifications are shown on Table 200.03. Table 200.04 shows values for design

elements related curvature.

to

speed

and

horizontal

Table 200.03 Maximum Superelevation Rates Roadway Classification Freeways Expressways Ramps Main Roads and Collectors Sector Roads 202.03

emax 0.06 0.06 0.06 0.04 Normal Crown

CITY ROAD CONDITIONS

Lower superelevation rates may be necessary in urban areas where restricted speed zones or intersections are controlling factors. In addition, existing road grades, curbs, or drainage may prove difficult to alter. Such conditions may warrant, for example, a reduction in the superelevation rate, different rates for each half of the roadbed, or both. In warping road areas for drainage, adverse superelevation should be avoided.

Part 2 200-4


Table 200.04 Values for Design Elements Related to Speed and Horizontal Curvature From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets” Part 2 200-5


202.04

AXIS OF ROTATION

Aesthetics, grade distortion, superelevation transitions, drainage, and driver perception should be considered when selecting the axis of rotation. Undivided Roadways - The axis of rotation shall be at the roadway centerline. However, in special cases changing the axis of rotation to the inside travelled way edge can avoid drainage problems caused by superelevation, or, improve curve perception for curves preceded by long relatively level tangents. Expressway Connections and Ramps - The axis of rotation may be about either edge of travelled way or centerline if multinale. Appearance and drainage considerations shall be considered when selecting the axis of rotation. Divided Roadways - The axis of rotation shall be at the median edge of each travelled way. However, for bridges with decked medians the axis of rotation shall be at the centerline. 202.05

SUPERELEVATION TRANSITION

General - Superelevation transition should be designed in accordance with Figure 200.04. The length of superelevation transition should be based upon the combination of superelevation rate and width of rotation plane. Edge of travelled way and shoulder profiles should be plotted and irregularities and drainage problems should be eliminated. Superelevation Transitions - Roadways separated by barrier or median will be superelevated at independent rates. The transition length will be based on pavement width and superelevation change. The profile of the outside edge of through pavement cannot differ from the profile gradeline by more than the percentage shown on Table 200.04 and will be an unbroken line throughout the transition. The minimum transition length for a two lane roadway is shown on Table 200.04. For multiple lane roadways the minimum length shall increase proportionately.

An example of expressway superelevation development is shown on Figure 200.04. For roadways on the inside of the curve, the outside shoulder will begin rotating when the inside roadway pavement has reached a superelevation of -3.0 percent (normal shoulder slope). When superelevation becomes greater than -3.0 percent, the pavement and shoulder will rotate in unison. The location of a superelevation transition, with respect to the point of curvature, will be determined using the inside roadway transition. Approximately one-third of the transition length will be placed on the curve. The remaining transition length will be on the tangent. The transition location will be adjusted to begin/end at a 10 meter station. For roadways on the outside of the curve, the transition will begin/end at the adjust the curve determined by the inside roadway transition. An additional transition length is required to rotate the outside shoulder from -3.0 percent (normal shoulder slope) to -1.5 percent (normal pavement slope). This shoulder transition length must be added to the pavement transition length to get the total transition length. Restrictive Areas - In restrictive areas, where full superelevation cannot be achieved, the highest possible superelevation rate and transition length shall be used. But, in no case shall the cross slope rate of change exceed 4% per 20 m. Superelevation Transitions on Bridges Superelevation transitions on bridges should be avoided. 202.06

SUPERELEVATION OF COMPOUND CURVES

Compound curve superelevation shall be per Figure 200.05. Where feasible, the criteria in Section 202.05 shall apply.

Part 2 200-6


Figure 200.04 Freeway/Expressway Superelevation Transitions Part 2 200-7


Figure 200.05 Superelevation Transitions for Compound Curves Part 2 200-8


If a glare screen or median barrier is used, adjustments may be necessary to maintain the required sight distance on divided roadway curves.

HORIZONTAL ALIGNMENT GENERAL

Horizontal alignment consists of a series of circular curves and tangent sections. The horizontal alignment should provide safe continuous uniform operation for substantial roadway lengths. The major factors influencing horizontal alignment design are safety, profile, type of facility, design speed, cost, geotechnical constraints, topography, aesthetics, and functionality. All of these factors must be balanced to produce the safest, most economical alignment, which is in harmony with the natural contour of the land, and at the same time adequate for the design classification of the roadway. In design, safety is always a major factor. The horizontal alignment shall provide at least the minimum stopping sight distance for the chosen design speed at all points along the roadway. The following standards apply to horizontal curvature on both 2-lane and multilane roadways except as noted. 203.02

STANDARDS FOR HORIZONTAL CURVATURE

Minimum Curvature - Table 200.05 gives the minimum curve radius based on design speed. Table 200.05 Standards For Curve Radius Roadway Minimum Classification Curve Radius (m) RURAL Freeway 2000 Expressway 2000 Collector 600 Local Access 100 URBAN Freeway 600 Expressway 600 Arterial (Main Rd) 600 Frontage Road 600 Sector Road 100 LOOP RAMPS 45 This table assumes unlimited sight distance. Minimum radius should also be checked against Figure 200.03. Every effort should be made to exceed the minimum.

Alignment Consistency - Sudden reductions in alignment standards shall be avoided. Introduction of curves with lower design speeds shall be avoided at the end of long tangents, steep downgrades, or at other locations where high approach speeds may be anticipated. In no case shall the design speed between successive curves change more than 15 kph. On roadways in mountainous or rolling terrain where horizontal and vertical curves are superimposed at grade summit or sag, the design speed of the horizontal curve should be at least equal to that of the crest or sag, and not more than 15 kph less than the measured or estimated running (85th percentile) speed of vehicles on the approach roadway. Curve Length and Central Angle - For central angles less than 10 degrees, the minimum curve length should be 240 m to avoid a kinked appearance. For central angles smaller than 30 minutes, no curve is required. Above a 6000 m radius, parabolic curves may be used. In no case shall sight distance or other safety considerations be sacrificed to meet the above requirements. Lane curve lengths in excess of 800m on 2-lane roadways should be avoided in consideration of the safety aspects associated with driver attentiveness and oncoming headlight glare. On 2-lane roads a curve should not exceed a length of 800 m. Compound Curves - Compound curves shall be avoided, except where use of a simple curve results in excessive cost. If compound curves are used, the shorter radius should be at least two-thirds the longer radius when the shorter radius is 300 m or less. The total arc length of a compound curve should not be less than 150 m.

Part 2 200-9

ROADWAY DESIGN MANUAL – Roads and Bridges Reverse Curves - When horizontal curves reverse direction the connecting tangents shall be long enough to accommodate the standard superelevation runoffs given on Figure 200.04. In no case shall the cross slope rate of change exceed 4% per 20 m. Broken Back Curves - A broken back curve consists of two curves in the same direction joined by a short tangent section. Broken back curves are unsightly, undesirable and should be avoided. Alignment at Bridges - If possible, a bridge should be located entirely on a tangent or curve because superelevation transitions on bridges almost always result in unsightly bridge and bridge railing appearance. However, alignment and safety considerations shall govern. Intersections and Interchanges - If possible, intersections should be on tangent sections or flat horizontal curves with very little superelevation. Interchanges, such as a typical diamond interchange, include two closely spaced at-grade intersections that function inter-dependently. A tangent alignment should be maintained between intersections for signal visibility and lane assignment determinations required by the motorist.

204 204.01

VERTICAL ALIGNMENT GENERAL

Vertical alignment consists of a series of grades connected by parabolic vertical curves. It is used to establish elevations for all roadway features. It is controlled mainly by topography, roadway class, horizontal alignment, safety, sight distance, costs, cultural development, drainage, and aesthetics. Steep grades affect truck speeds and overall capacity. All portions of the vertical alignment shall meet minimum sight distance requirements.

204.02

VERTICAL ALIGNMENT POSITION WITH RESPECT TO CROSS SECTION

The grade line should generally coincide with the axis of rotation for superelevation. Its relation to the cross section should be as follows: Undivided Roadways - The grade line should coincide with the roadway centerline. Expressway Connections and Ramps - The grade line may be positioned at either edge of travelled way or centerline if multilane. Divided Roadways - The grade line may be positioned at either the median centerline or at the ultimate median edge of travelled way. The former case is appropriate for paved medians 9 m wide or less. The latter case is appropriate when: a) b) c) 204.03

The median edges of travelled way of the two roadways are at equal elevation. The roadways are at different elevations. The median width is ununiform. STANDARDS FOR GRADES

Maximum Grades - Table 200.06 lists the maximum grades for design for rural roadways based on design speed and urban roadways based on roadway type. Minimum Grades - The desirable minimum grades should be not less than 0.3 percent for curbed pavement sections and 0.2 percent in very flat terrain. Minimum grades can be maintained in very flat terrain by use of a rolling profile. In developed urban areas with extremely flat terrain, flatter minimum grades may be warranted in consideration of adjacent building elevations and offsite drainage problems associated with rolling profiles. The use of minimum grades flatter than those specified above will require case by case approval by the Road Section.

Part 2 200-10

ROADWAY DESIGN MANUAL – Roads and Bridges Table 200.06 Grade Standards Rural Design Speed (kph) 60 70 80 90 100 110 120 130 Urban Roadway Type

Level

Rolling

%

%

5 5 4 4 3 3 3 3

Freeway Expressway Ramps Arterial (Main Rd) Frontage Road Sector Roads 204.04

Mountainous %

6 6 5 5 4 4 4 4 Desirable Maximum %

8 7 7 6 6 5 5 4 Absolute Maximum %

3 3 4 2 2 2

4 4 6 3 3 3

Consideration should be given to adding lanes where the truck speed reduction is greater than 15 kph and there is a significant reduction in levelof-service when moving from the approach segment to the grade. On two lane roadways, a climbing lane should be considered when, in addition to the above criteria, the upgrade traffic flow is in excess of 200 vehicles per hour and the truck factor is in excess of ten percent. Decision sight distance should be provided at climbing lane drops on expressways. 204.06

STRUCTURE GRADE LINE

Structure Depth - The depth to span ratio for a structure is dependent on many factors. Use a structure depth to span ratio of 0.04 to 0.045 for preliminary design purposes.

VERTICAL CURVES

Parabolic vertical curves are used in roadway design per Figure 200.06. Figures 200.07 and 200.08 will be used to obtain vertical curves lengths. For design speeds greater than 65 kph, the minimum vertical curve length should be 120 m. For 50 kph design speed, it should be 60 m. Flat vertical curves may develop poor drainage in the level section. Adjusting the edge grade or shortening the vertical curve may be required. Design of these long vertical curves should be avoided because many drivers will not pass on curves over 1 km long, despite adequate sight distance. It may be more economical to construct passing lanes than to obtain passing sight distance by using a long vertical curve. 204.05

grade length must be considered because it has a major effect on operational speed, capacity, level of service, and contributes to heavy truck delays. Figure 200.09 shows the speed reduction in kph for an assumed typical heavy truck of 180 kg/kW as a function of grade length and upgrade percent. Generally, a truck speed reduction of up to 15 kph does not significantly impact roadway capacity.

LONG SUSTAINED GRADES

The maximum grade guideline is not sufficient to insure uniform roadway operation. The uphill

Falsework Allowance - To establish the grade of a structure constructed with a falsework opening, allowance must be made for the falsework depth. The minimum vertical falsework clearance over primary and secondary roadways shall be 4.8 m. The minimum vertical falsework clearance over local roadways shall be 4.5 m. Bridge Deck Drainage - Vertical alignment design requires special consideration of structure drainage. Zero gradients and sag vertical curves should be avoided on bridges. Parapets collect large amounts of debris and smaller bridge deck drains or scuppers have a higher potential for clogging. The minimum desirable longitudinal slope for bridge deck drainage is 0.2 percent. Where vertical curves on bridges cannot be avoided, the elevations should be checked to provide a minimum effective longitudinal grade of 0.5 percent, and not extend more than 15 m either side of the sag or crest point.

Part 2 200-11


Figure 200.06 Symmetric Parabolic Vertical Curves Part 2 200-12


Figure 200.07 Design Controls for Crest Vertical Curves, for Stopping Sight Distance- Upper Range. From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets” . Part 2 200-13


Figure 200.08 Design Controls for Sag Vertical Curves - Upper Range. From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets”. Part 2 200-14


Figure 200.09 Critical Lengths of Grade for Design, Assumed Typical Heavy Truck of 180 kg/kW, Entering Speed 90 kph. From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets”.

Part 2 200-15


SEPARATE PROFILE GRADE LINES •

Separate grade lines should be considered for all divided roadways. The use of separate grade lines provides the opportunity to optimize the vertical alignment, drainage features, and provide a safer more economical design.

• •

They are not normally considered appropriate where medians are less than 18 m wide. Exceptions to this may be minor differences between opposing grade lines in special situations. In addition, for either interim or ultimate expressways, any appreciable grade differential between roadbeds should be avoided in the vicinity of at-grade intersections. For traffic entering from the crossroad, confusion and wrong-way movements could result if the pavement of the far roadway is obscured because of excessive differential.

205

COORDINATION OF HORIZONTAL AND VERTICAL ALIGNMENTS

The coordination, of horizontal and vertical alignments is based on experience and engineering judgment. Successful coordination is essential for a safe well balanced design. The following are guidelines to be used, where possible. •

•

•

•

•

high approach speeds may result in erratic operation, especially at night. For moderate changes in horizontal alignment at grade summits, the horizontal curve should overlap the vertical curve. Avoid successive changes in profile which are not associated with horizontal curves. The succession of humps is unattractive. Horizontal and vertical curvature at intersections should be as flat as physical conditions permit. Avoid excessive curvature to obtain flat grades and tangent alignment or flat curves at the expense of steep or long grades. It is better to balance horizontal and vertical alignments. In general, alignments should be designed to take full advantage of scenic opportunities.

206 206.01

GENERAL

A pavement transition occurs when changing from one roadway cross section to another. If feasible, the transition should occur on a tangent section. And be entirely visible to the driver. Avoid locations with sight distance restrictions. Transitions should not occur within at-grade intersections. Decision sight distance shall be provided at all lane drops. 206.02

Vertical curves should be superimposed on horizontal curves. This reduces the number of sight restrictions, makes profile changes less apparent, and results in a pleasing appearance. However, when superimposed, the superelevation and profile grade combination may distort the outer pavement edges, confusing drivers at night. In such situations edge of pavement profiles should be plotted and smooth curves introduced to eliminate distortion. Avoid sharp horizontal curvature at or near the top of a crest vertical curve. This condition makes it difficult for the driver to perceive the curve, especially at night when headlights do not illuminate the curve. Avoid sharp horizontal curvature at or near the low point of a sag vertical curve. Foreshortening of the horizontal curve and

PAVEMENT TRANSITIONS

TRANSITIONS FOR MULTILANE ROADWAYS

Four Lanes to Two Lanes - A typical transition between 4 lanes and 2 lanes is shown in Figure 200.10. The alignment and the unspecified radius of curvature varies depending on median width and other site considerations. Lane Drop - The minimum taper length for a lane drop should be equal to 0.6WV, where W = Dropped Lane Width (m), and V = Design Speed (kph). The transition should be on the right so that traffic merges left. Lane Addition - The minimum taper rate to add a lane should be 25:1 but in no case shall the taper length be less than 50 m.

Part 2 200-16


Figure 200.10 Typical Two-Lane to Four Lane Transitions Part 2 200-17


208.02

BRIDGES AND GRADE SEPARATION STRUCTURES CLEAR WIDTH

The clear curb to curb width of all bridges or grade separation structures shall equal the sum of the full travelled way approach width, paved shoulders and barrier offset (if any). 207.02

CROSS SLOPE

The cross slope shall be the same as the approach pavement. The crown is normally centered on the bridge except for one-way roadways where a straight crosslope in one direction should be used. 207.03

SIDEWALKS

Sidewalks should be provided where justified by pedestrian traffic or if the approach roadway has sidewalk. The sidewalk width should match the approach sidewalk width and crosslope.

208 208.01

PEDESTRIAN FACILITIES SIDEWALKS

Sidewalk widths and locations vary but they shall have a minimum width of 2.0 m and be located to provide continuity in pedestrian movement. Pedestrian crosswalk ramps shall be located at all intersections and all other locations where main pedestrian traffic crosses curblines. Cross Slope - The minimum sidewalk cross slope should be 1.5% toward the roadway. Sidewalk Widths - The guidelines in Table 200.07 should be used to determine sidewalk width.

Pedestrian grade separations are not normally provided on roadways. However, if pedestrian use is extensive, an overcrossing or undercrossing may be considered. Justification for pedestrian grade separation structures comes from the detailed study of present and future community needs. Each situation should be studied separately and the study should include pedestrian generating sources, travel patterns, crossing volumes, roadway classification, location/circuitry of adjacent crossings, land uses, sociological and cultural factors, and the predominant type and age of users. Established pedestrian patterns should be maintained across expressway routes. Separate pedestrian structures should be provided if vehicular crossings are inadequate for pedestrians. If a circuitous route is involved, a pedestrian separation may be justified. Special consideration should be given to school crossings. The choice between an undercrossing or an overcrossing should be based on relative costs, groundwater influence, drainage, existing utilities, current and future land use, visibility, topography and the surrounding architecture. 208.03

Area/ vicinity Multi Family Units/Schools/ Office/Industrial Shopping/Recreation/Bus/Taxi

PEDESTRIAN UNDERPASSES

Undercrossings require special consideration, visibility issues and the potential for criminal incidents and vandalism. If an undercrossing is used, unobstructed visibility shall be provided through the structure and approaches. The desired vertical clearance is 3.0 m, but in no case shall the clearance be less than 2.0 m. The minimum width shall be 2.5 m.

209 Table 200.07 Sidewalk Width Guidelines

PEDESTRIAN GRADE SEPARATIONS

209.01

CURBS GENERAL

Width (m) Curbs will be provided along all edges of pavement in urban areas. Reasons for providing Curbs include:

2.0 4.0

The minimum sidewalk width shall be 2.0 m.

Part 2 200-18

ROADWAY DESIGN MANUAL – Roads and Bridges • • • • •

Required for proper drainage. Needed for channelization, delineation, control of access, or improving traffic flow and safety. To protect pedestrians and provide continuity at ramp connections with local roads. To replace existing curbs. To protect the expressway fence on frontage roads where required.

209.02

TYPES AND USES

Curb types and uses are shown in the current Standard Drawings and are discussed below. Precast Curb Type A, B, C - These curbs are used to deter vehicles from using areas outside the travelled way, control drainage, and regulate and control parking. Type A curbs are typically used on the outside of the travelled way, adjacent to sidewalks and parking lanes. Typical B and C curbs are used at the median edge adjacent to the green area. The above curb types are classified as barrier curbs and are not generally used on high-speed roadways as they present a safety hazard for errant vehicles. A continuous concrete barrier (safety shape) should be used where it is necessary to control drainage or access on highspeed roadways. Cast-In-Situ Concrete Curb Type D - This curb is flush with the pavement and used to separate the travelled way from interlocking vehicular pavement. Precast Concrete Curb Type E - This curb is used between interlocking pedestrian pavers and green or service reservation areas. Cast-In-Situ Concrete Curb Type F - This curb is flush with the pavement and used to separate interlocking pedestrian pavers from quarry tile. 209.03

Transitions - A transition from one curb type to another shall be done in 3.0 m. At curb termini, the curb should transition from normal curb height to zero in 5.0 m.

210

BUS STOPS AND TAXI STOPS

In urban areas, bus stops and taxi stops will be provided on all main roads. To prevent ponding in bus and taxi stops on flat grades use either a reverse cross slope toward the main road pavement with slotted trench drains or continue the slope of the roadway and install an inlet along the loading/unloading curb line. 210.01

BUS STOPS

Bus stops will be located at the far side of intersections and as necessary at midblock locations. Near side bus stops should be avoided. Normally, bus stops shall be constructed as shown on the current Standard Drawings. Under restrictive conditions these standards may be reduced to 15.0 m length, 10.0 m tapers and 3.25 m width. At all bus stops a 4.0 m wide sidewalk shall be provided along the loading/unloading area. This shall be connected to the nearest sidewalk with a 4.0 m wide perpendicular sidewalk. 210.02

TAXI STOPS

Taxi stops will be located at the far side of intersections, no closer than 30.0 m to the radius return or end of right turn taper. Taxi stops should be located as necessary within the block but no closer than 30.0 m to a sector road. Taxi stops shall be constructed as shown on the current Standard Drawings. At all taxi stops a 4.0 m wide sidewalk shall be provided along the loading/unloading area. This shall be connected to the nearest sidewalk with a 4.0 m wide perpendicular sidewalk.

CURB PARAMETERS

Placement - Curbs should be positioned to provide the same unobstructed roadway width that is normally provided. All curb dimensions are to the inside face of curb. Part 2 200-19


PARKING

To maximize the effective capacity of expressway and main road improvements, sufficient offsystem parking facilities should be provided to avoid the need for curb lane parking along primary expressways and main roads. 211.01

GENERAL

Parking facilities are of four general types: 1.

2.

3. 4.

Parking areas located parallel to, but physically separated from, main road moving traffic lanes, On-road parking spaces developed adjacent to the travelled lanes of sector roads, and Independent parking lots developed off sector roads. Parking Structures.

Each facility consists of an “aisle” area and a “standing area” (parking stalls). In the case of onroad parking, the moving lanes of the sector road also serve as the aisle. Figure 200.11 illustrates different forms of the basic types of parking facilities. 211.02

PARKING AREAS

Lots P1 and P2 on Figure 200.11 are typical “parking areas,” characterized by one entrance off the main road, then an aisle area with adjacent perpendicular and/or 45 degree parking, and finally an exit leading back onto the main road travel lanes. Desirably, the entrances and exits should be independent of any sector road or main road intersections (i.e., Lot P2). When physical conditions prevent this, a common entrance (or exit) may be an acceptable arrangement (i.e., Lot P1). The minimum safe distance from a main road intersection to a parking entrance or exit will be dependent on many factors, such as, volume and speed of the traffic, type of intersection, width and number of lanes in the main road, the volume of traffic using the parking area, and any sight distance restrictions.

Generally it is desirable to locate parking exits onto main roads about 50 meters prior to the start of the left turn storage lane, and parking entrances off of main roads about 60 meters prior to the intersection, and/or prior to the start of the free right turn taper. In the typical case, a “parking area” is physically separated from the main road lanes by a curb/sidewalk/curb combination which has been designated as a “wide curb”. See Lot P2 in Figure 200.11. The minimum distance between the faces of the two curbs is 1.0 m. The parking area edge nearest the buildings should be set parallel to the building line and at a sufficient offset distance to allow a sidewalk along the building line. The current Standard Drawings illustrate typical parking area and show stall dimensions and pavement markings for both perpendicular and 45-degree parking arrangements. Aisle widths and stall depths should be as per Table 200.08. Table 200.08 Parking Isles and Stall Depths Parking Aisle Width Angle (m) Absolute Desirable Min Min 90o 60o 45o

7.0 5.0 4.5

211.03

7.3 5.5 5.0

Stall Depth (m) Absolute Desirable Min Min 5.5 5.7 5.3

5.8 6.0 5.6

ON ROAD PARKING SPACES

Parking spaces along sector roads are developed by constructing added pavements immediately adjacent to the sector road moving lanes (usually two lanes with one lane for travel in each direction). Such parking spaces should be either parallel or perpendicular. The use of 45-degree parking should be limited to one-way sector roads. Figure 200.11 shows examples of on-road parking space developments along sector roads. Dimensions for perpendicular and 45-degree

Part 2 200-20

ROADWAY DESIGN MANUAL – Roads and Bridges parking stalls are similar to those given on the Standard Drawings. Parallel parking stalls should have a length of 7.0 m and a desirable minimum width of 2.5 m as shown on the Standard Drawings. Where sector roads are widened to provide parking stalls, the widened sector road arrangement should not be carried through sector road/sector road intersections. The fillets at such intersections (usually 5.0 m radii) should be positioned to line up with the edge of the travelled lanes. 211.04

The required analysis regarding parking will thus vary from project to project since parking demand is sensitive to site-specific factors, such as land use and proposed community developments. In the absence of site specific parking criteria, Table 200.09 should be used. Also refer to Part 1, Section 202.02.11 for further parking requirements. Table 200.09 Parking Requirements

PARKING LOTS

Figure 200.11 also shows samples of independent parking lots developed off sector roads. Such lots are of two general varieties: 1. Single entrance/exit (see lots P3, P4 and P5) and 2. Double entrance/exit (see Lots P6 and P7). Wherever practical, these layout rules should be followed: 1. Aisles and entrance/exit widths should be typically designed for two-way operation in conjunction with perpendicular parking. 2. A median (curb/sidewalk/curb combination) at least 1.0 m wide should be provided between adjacent parking bays served off different aisles (i.e., on Figure 200.11, a barrier is provided between Lots P6 and P7). 3. Forty-five degree parking should only be used in conjunction with one-way aisles/sector roads. 211.05

3. determine the need for added parking facilities and establish an approximate location for such parking.

PARKING DEMAND/SUPPLY ANALYSIS

During the early portion of the Concept Design Phase, the designer will: 1. determine the location of existing parking facilities, 2. identify any facilities to be displaced by road improvements that should thus be replaced, and

Type of Development Requirements Commercial/Office space Retail space Governmental space School plus Hospital plus

Parking 1 space / 50 m2 floor 1 space / 30-50 m2 floor 1 space / 50 m2 floor 1 space / 3 employees 1 space / 5 students 1 space / 2 employees 1 space / 4 beds

Low Density Residential Villas Medium Density Apartments m2*.85*.80) High Density Apartments m2*.85*.80)

2 spaces / dwelling unit 1

space

/

(100

1

space

/

(100

These requirements should be considered as minimums. It is possible that the number of spaces required by these guidelines cannot be provided due to space limitations. In that case, efforts should be directed toward providing the maximum amount of parking in a reasonable configuration.

Part 2 200-21


Figure 200.11 Typical Parking Facilities

Part 2 200-22


SECTION 300 GEOMETRIC CROSS SECTION 301

TRAVELLED WAY STANDARDS

most urban roads because curbs provide pavement structural support, and disabled vehicles can park in parking lanes, side streets, or driveways. 302.01

301.01

TRAVELLED WAY WIDTH

Travelled way width is one of the most important safety factors in design. A wide two-lane two-way pavements provides higher capacity, higher driver comfort levels, consistent operation and lower accident rates. Minimum travelled way widths of 7.30 m shall be provided on all design classes of roadways. Traffic lane widths shall be 3.65 m, and the number of lanes required shall be based on the projected traffic volume and roadway classifications. Loop ramp lanes shall be 5.0 m. See Section 302 for general shoulder widths and see Section 305 for specific roadway cross section widths. 301.02

TRAVELLED WAY CROSS SLOPES

Tangent cross slope is balanced between steep cross slopes, desirable for drainage and the fact that vehicles drift toward the lower pavement edge on steep cross slopes. Generally, cross slopes below 1.5 percent have little effect on vehicle steering. Cross slope values for the various roadway classifications are provided in the following sections. Unpaved travelled ways shall have a cross slope of 3.0 percent. See Section 305 for specific roadway cross slope rates. Pavement superelevation on curves shall be as determined in Section 202.

302

SHOULDER STANDARDS

Shoulders provide pavement structural support, improve sight distance, provide emergency stopping areas, and help provide required side clearance. However, shoulders are unnecessary on

SHOULDER WIDTH STANDARDS

Table 300.01 summarizes the minimum continuous usable width of paved shoulder for various roadway classifications. Table 300.01 Paved Shoulder Width Standards Roadway Inside Outside Class Shoulder Shoulder / verge / verge (m) (m) RURAL Freeway 3.0 4.0/2.0 Expressway 3.0 4.0/2.0 Collector 2.4 Local Access 2.0 URBAN Freeway 3.0 4.0/2.0 Expressway 3.0 4.0/2.0 Arterial (Main Rd) 4.0/2.0 Frontage Road 1.2 1.2 Sector Road 2-LANE RAMP 2.4/2.0 3.0/2.0 LOOP RAMP 2.0/1.0 3.0/1.0 The verge is the area outside the paved shoulder, usually rounded, at the top of embankment slopes. 302.02

SHOULDER CROSS SLOPES

In normal tangent sections, inside shoulder slope shall match the travel lanes and outside shoulders shall slope on a 3% grade away from the travelled way.

303

SIDE SLOPE STANDARDS

Properly designed side slopes insure roadway stability and provide a safe recovery area for errant vehicles. Where feasible, slopes should be flattened to be consistent with the roadway classification and topography. The tops and ends of all slopes

Part 2 300-1

ROADWAY DESIGN MANUAL – Roads and Bridges should be rounded 3.0 m where the material is other than solid rock.

Shoulders - Shoulder widths for various roadway classifications are summarized in Table 300.01.

303.01

305.01

SIDE SLOPE VALUES

Side slopes should be 1:6 or flatter depending on soil type. If slopes are steeper than 1:3, barrier may be required. Earth cut slopes should be at least 1:3 but in no case steeper than 1:2. 303.02

SLOPE CLEARANCE FROM RIGHT OF WAY

The minimum clearance from the right of way line to the catch point should be 3.0 m with 4.5 m desired. For cut slopes this is measured from the outer edge of the rounding or crown drainage system. Slopes over 15.0 m high may require additional clearance for maintenance.

304

MEDIAN STANDARDS

A median is the portion of a divided roadway between the opposing travelled pavements. Raised medians shall be used on urban roads to regulate left-turn movements. Paved medians, including those bordered by curbs, should be crowned at the center, sloping towards the sides at the slope of the adjacent pavement. Unpaved, landscaped medians between curbs shall be graded flat. Other unpaved medians should slope downward from the shoulders to form a shallow valley. Cross slopes should be 1:10 or flatter 1:20 being preferred. Slopes as steep as 1:6 are acceptable if necessary for drainage.

General - The typical section for rural expressways shall be comprised of two roadways with shoulders, divided by a median. Travelled Roadways - Each roadway will consist of a minimum of three 3.65 m through lanes. Ramps shall be 5.0 m for one lane and, where volumes demand, two 3.65 m lanes. Median - Median treatment may be either standard concrete barriers placed along the inside shoulder edge or an unpaved depressed median. Median width may vary to match existing median widths. The width of the depressed median measured between edges of travelled pavement shall be 20.0 m minimum. Cross Slope - Except superelevated sections, a uniform cross slope of 1.5 percent shall be applied across the inside shoulder and driving lanes. The outside shoulder will have a crossslope of 3.0 percent. The pavement will slope toward the outside of the section. On structures, the cross-slope shall be 1.5 percent uniformly across the inside shoulder, driving lanes, and outside shoulder. Profile Grade Line - The profile grade line shall be at the median edge of the travelled roadway. 305.02

See Section 305 for specific roadway median requirements.

305

CROSS SECTION ELEMENTS

See Figure 300.01 for typical cross sections of various roadway classifications. Pavement Structure - For the Standard Pavement Structures, see current Standard Drawings. Also, refer to Section 604 Structural Pavement Section Design.

RURAL FREEWAY/ EXPRESSWAY CROSS SECTION

URBAN FREEWAY/ EXPRESSWAY CROSS SECTION

General - The typical section for urban expressways shall be comprised of two roadways, with shoulders, divided by a median. Due to space limitations, the cross section may vary. The final configuration shall be determined during the concept phase of design.

Part 2 300-2


Figure 300.01 Typical Cross Sections Part 2 300-3

ROADWAY DESIGN MANUAL – Roads and Bridges Travelled Roadways - Each roadway will consist of a minimum of three 3.65 m wide through lanes. Ramps shall be one 5.0 m lane, and where volumes demand, two 3.65 m lanes. Median - A minimum 7.0 m wide median shall be used. However, a 10.0 m median width is desirable. The median may be either unpaved and depressed (if 20.0 m wide or more), or it may have concrete barriers. Cross Slope - Except in superelevated sections, a uniform cross slope of 1.5 percent shall be applied across the inside shoulder and driving lanes. The outside shoulder will have a cross slope of 3.0 percent. The pavement will slope toward the outside of the section. On structures, the cross slope shall be 1.5 percent uniformly across the inside shoulder, driving lanes, and outside shoulder. Profile Grade Line - The profile grade line shall be the median edge of the travelled roadway. 305.03

ARTERIAL (MAIN ROAD) CROSS SECTION

The standard cross section of roadways is comprised of two unidirectional pavements, median, sidewalks, service reservations and green areas. Pavement and Lane Widths - The pavement will consist of a minimum of three traffic lanes in each direction divided by a raised median. Wherever necessary, auxiliary lanes shall be provided for turning movements. Auxiliary lanes, whether allocated to through traffic or to turning movements, shall be 3.65 m wide. Free Right Turn Islands and Lanes - Exclusive right-turn lanes and islands shall be used wherever possible. No more than one exclusive right-turn lane shall be provided in any direction.

Parking, Loading/Unloading Lanes - Except for taxi stops and bus stops, no parking or loading/unloading spaces shall be provided on main roads without being separated from the traffic lanes by a wide curb. Median - A median with 22 cm high curbs shall be provided. The median width should be at least 5.0 m. Where an existing street with a median of less than 5.0 m is being upgraded, the median should be increased to 5.0 m if possible. Where an existing street with a median width of greater than 5.0 m is being upgraded, the existing median width should be maintained for planting. Median width shall be reduced to permit exclusive leftturn lanes at intersections where required. No provision shall be made for U-turns except at intersections. Curbs - Curbs shall be provided along all edges of pavement in urban areas. Curb types and uses are shown in the current Standard Drawings. Sidewalks - Sidewalk widths and locations will vary but the minimum width shall be 2.0 m and they shall be located to provide pedestrian movement continuity. In addition, whenever possible a 2.0 m wide sidewalk adjacent to the pavement and green areas should be provided primarily for aesthetic purposes. Pedestrian crosswalk ramps shall be used at all intersections and all other locations where the main pedestrian sidewalk crosses curb lines. Cross Slope - All pavement will have a broken cross-slope of 1.25 percent sloping away from the median across the two inside lanes and 2.0 percent for the outside lanes. A 1.5 percent crossslope shall be provided toward the pavement on sidewalks. Cross-slope will vary at intersections in accordance with current Standard Drawings. Profile Grade Line - The profile grade line shall be the median edge of pavement.

Left Turn Lanes - Unless otherwise approved by the Municipality Road Section under special conditions, no more than one left-turn lane shall be provided from the median.

Part 2 300-4


SECTOR ROAD CROSS SECTION

305.05

The cross section for sector roads will consist of an undivided two-directional roadway. Curbs shall be provided along both edges of pavement. Pavement and Lane Widths - Lane width shall be 3.65 m for two lanes in each direction and 4.0 to 5.0 m for one lane in each direction. Free Right Turn Islands and Lanes - No free right turn islands or lanes shall be used in the design of sector roads. Left Turn Lanes - Left turn lanes shall not be used in the design of sector roads. Parking Loading/Unloading Lanes - Generally, no loading or unloading lanes shall be provided on Sector Roads. It is up to the designer and Design Project Manager to determine the need and type of on-street sector road parking. If required, see Section 211, Parking. Median - Sector roads shall not have medians. Curbs - Curbs shall be provided along the outside edge of sector roads. Types and uses are shown in the current Standard Drawings.

Pavement and Lane Widths - The minimum paved cross section for urban frontage roads shall be two 3.65 m lanes with curbing. The minimum paved cross section for rural frontage roads shall be 3.65 m lanes with 1.2 m paved shoulders. Cross Slope - All pavement will have a 1.5 percent uniform cross slope either at a straight cross slope from one edge of pavement to the other or by utilizing a crowned roadway design. Outer Separation - Outer separation is the distance from the main road travelled way to the frontage road travelled way. In urban and mountainous areas, the outer separation should be 8.0 m minimum. In rural areas, other than mountainous terrain, the outer separation should 12.0 m minimum. Headlight Glare - Frontage road design shall account for potential headlight glare interfering with the vision of oncoming motorists. The preferred measures to prevent headlight glare interference on new construction are wider outer separations, revised alignment and raised or lowered profiles.

306 Sidewalks - Sidewalk widths and locations will vary but minimum width shall be 2.0 m. Whenever possible a 2.0 m wide sidewalk dividing the pavement and green areas should be provided. The sidewalk surface will slope toward the roadway at a uniform cross slope of 1.0 percent. Pedestrian crosswalk ramps shall be used at all intersections and all other locations where main pedestrian traffic crosses curb lines.

FRONTAGE ROAD CROSS SECTION

306.01

HORIZONTAL AND VERTICAL CLEARANCES HORIZONTAL CLEARANCES

Unshielded Horizontal Clearance - The minimum desired horizontal clearance between the travelled way edge and fixed objects shall be the clear zone width. Fixed objects within the clear zone shall be eliminated, moved, redesigned (breakaway design), or shielded (see barrier design below ) where practical.

Cross Slope - All pavement will have a 1.5 percent uniform cross slope either at a straight cross slope from one edge of pavement to the other or by utilizing a crowned roadway design. Sector roads shall not have superelevation.

Shielded Horizontal Clearance - If fixed objects cannot be eliminated, moved or redesigned then lesser clearance is allowable if barriers or guardrail is used to shield the object.

Profile Grade Line - The profile grade line for sector roads shall be the centerline or as determined by the Consultant.

The clearance to fixed objects such as bridge rails, concrete barriers, abutments, retaining walls or noise barriers on all roadway facilities, shall be equal to the standard roadway shoulder

Part 2 300-5

ROADWAY DESIGN MANUAL – Roads and Bridges width stated in Table 300.01, except that a minimum clearance of 1.2 m shall be provided where the standard shoulder width is less than 1.2 m. Approach rail connections to bridge rail may require special treatment to maintain standard shoulder width. Safety shaped barrier face shall be constructed integrally at the base of any retaining wall, pier, or abutment which faces traffic and is less than 4.6 m from the edge of travelled way. Curbed Roadway Sections - A minimum horizontal clearance of 1.0 m should be provided along intersection curb returns and near driveway edges to allow for design vehicle off tracking. Where sidewalks are located immediately adjacent to curbs, fixed objects should be located behind the sidewalk, providing an unobstructed pedestrian area.

306.03

Horizontal Clearances - The minimum expressway tunnel width should equal the full approach travelled way width plus paved shoulders. In one-way tunnels on conventional roadways the minimum side clearance from the edge of the travelled way (unless sight distance dicatates otherwise) shall be 1.5 m on the left and 2.0 m on the right. For two-way tunnels, this clearance shall be 2.0 m on each side. Vertical Clearances - The desirable vertical clearance shall be 6.0 m measured at any point over the travelled way. Lesser clearance may be approved by the Municipality Road Section.

307 306.02

TUNNEL CLEARANCES

CLEAR ZONE CONCEPT

VERTICAL CLEARANCES

General - Efforts should be made to avoid decreasing the existing vertical clearance whenever possible and consideration should be given to increasing vertical clearance on projects involving structural section removal and replacement. Structure Type

Vertical Clearance (m)

Pavement Surface to nearest underside of superstructure.

6.0

Sign Structures

5.5

Overhead Communication Lines

7.0

Power Lines

(Volts) 0 - 750 750 - 15,000 15,000 and greater

7.0 9.0 10.0

Pedestrian Overpass

6.0

Pedestrian Overpass with Overhead Guide Sign

6.0

Clear Zone - A clear zone is an unobstructed, flat or gently sloping area beyond the travelled way edge. It gives drivers the opportunity to regain control of errant vehicles. The clear zone is measured horizontally from the travelled way edge to the nearest point on an obstruction. Where feasible, fixed objects should not be located within the clear zone. In an area where the roadside is relatively clear, flat and straight, application of the clear zone concept is straightforward. However, factors such as roadside embankments, space restrictions and roadway curvature and superelevation complicate the application of the clear zone. Clear Zone Standard - The clear zone width required is based on geometry, traffic volumes, and operating speeds as shown on Figure 300.02. Curvature Correction Factors - Figure 300.03 shows correction factors used to adjust the clear zone distances, taking into account roadway curvatures. These modifications should be used only in locations with high accident rates and where increasing the clear zone distance is cost effective.

Part 2 300-6


Figure 300.02 Clear Zone Distance Curves Part 2 300-7


Figure 300.03 Horizontal Curve Adjustments Factors

307.01

307.01.01

APPLICATION OF CLEAR ZONE Roadside Terrain: Foreslope

When a roadway is on an embankment, the side slope is called a foreslope (negative slope) which can be recoverable, non-recoverable, or critical: Recoverable - A recoverable slope is one that an errant vehicle can drive across, slow down, stop, and return to the roadway. Recoverable slopes are 1:4 or flatter, relatively smooth, and clear of all fixed object hazards. The top of the slope shall be rounded so a vehicle’s wheels remain in contact with the roadway when encountering the embankment. The toe of slope shall also be rounded so the driver is able to negotiate and drive across if the vehicle reaches the base of the embankment. Non-recoverable - A non-recoverable slope is one which an errant vehicle can be driven across but may not be able to slow down or stop before

reaching the base. Embankments with slopes between 1:3 and 1:4 generally fall under this category. A smooth clear run-out area with a slope of 1:6 or flatter, in addition to the recommended clear zone distance is recommended at the base of the slope. The width of the runout area is determined according to the available width between the edge of traveled way and the breakpoint between the flatter (1:4 and flatter) and steeper (1:4 and 1:3) slope of the embankment. This available width is then subtracted from the clear zone distance obtained from Figure 300.02, based on the steeper slope of the embankment. The difference is the width of the clear runout area. See Figure 300.04 for example. Critical - A critical slope is one where a vehicle has a high probability of overturning, slopes steeper than 1:3 fall in this category. If the available clear zone is narrower than the recommended width or it is not practical to adjust the roadside geometry, installing a barrier system may be necessary.

Part 2 300-8

ROADWAY DESIGN MANUAL – Roads and Bridges 307.01.04 307.01.02

Roadside Terrain: Backslope

When a roadway is located in a cut section, the cut slope is called a backslope. A traversable backslope is 1:3 or flatter, relatively smooth, clear of fixed object hazards, and where a vehicle can be driven across without becoming stranded. This type of backslope can be included as part of the clear zone. However if the backslope is steeper than 1:3, rock cut or rough sided, the base of the backslope shall be outside the clear zone. If the recommended clear zone can not be practically accommodated, a barrier system may be required to protect motorists. 307.01.03

Roadside Terrain: Cross-slope

Cross-slopes can be located along medians, intersecting driveways and roadways. Cross slopes can be more hazardous to motorists than foreslopes or backslopes because of the possibility of colliding with opposing traffic. Cross-slopes of 1:10 or flatter, traversable, relatively smooth, and clear of fixed object hazards are recommended particularly in medians immediately adjacent to opposing traffic. In roadside sections where 1:10 can not be accommodated, such as urban areas, a maximum slope of 1:6 should be used.

Roadside Terrain: Ditch

The primary function of ditches is to prevent roadways from flooding by directing and carrying water away from the roadway. They are especially hazardous because of fixed hazards such as, exposed pipes, headwalls and culverts. The ditch cross section itself can also represent a serious hazard. Preferred ditch cross sections are traversable and free of hazards. See Figures 300.05 and 300.06. Cross sections that fall within the shaded area are considered traversable. Cross sections that fall outside the shaded regions are considered less desirable and should be used only under conditions of: • restricted ROW • rugged terrain • resurfacing, restoration or rehabilitation • low volume or low speed roads Conditions where a ditch has a cross section that falls outside the shaded region, and is located in a vulnerable location shall consider closed drainage systems or shielding with barrier systems.

Figure 300.04 Clear Runout Area

Part 2 300-9


Figure 300.05 Preferred Vee-Ditch Cross Sections

Figure 300.06 Preferred Trapezoidal ditch Cross Sections Part 2 300-10


•

BARRIERS BARRIER NEED

•

The roadside barrier’s primary function is to prevent errant vehicles from leaving the roadway. Barrier need is based on the premise that installing a barrier will reduce the number of accidents and/or reduce the magnitude of an accident at that location. The engineer must also evaluate the barrier installation itself to be less hazardous than the hazard. Efforts shall be made to eliminate hazards within the clear zone prior to considering any barrier installations. When determining barrier requirements, the following factors must be considered: • Risks involved with encroaching on a hazard versus colliding with a barrier. • Evaluating roadway design speed and traffic volumes to barrier need. • Evaluating costs of installing and maintaining a barrier system versus not installing a barrier system. • Costs of accidents involving barriers versus not involving a barriers. Figure 300.07 for example, compares the risks involved with encroaching on an embankment versus colliding with a barrier. Embankments that fall outside the shaded region do not warrant shielding. Figure 300.07 however does not not take into account other factors such as, object hazards on the embankments within the clear zone, installation and maintenance costs of a barrier system, and accident costs involving a barrier system. All these factors must be considered together when evaluating barrier needs. As previously stated, if hazards exist within the borders of the clear zone, efforts shall be made to eliminate the hazard first, prior to considering barrier installation. These considerations can include any of the following: • Regrading of roadside topography in the clear zone to a smooth and safe cross section. • Extend exposed pipes, culverts and install headwalls outside the clear zone.

•

Install drop inlets for roadside drainage systems rather than exposed pipes and culverts. Remove or relocate all manmade or natural fixed obstacles such as utility poles, signs, luminare supports, trees, and boulders. Install breakaway bases for signs and luminare supports if removal or relocation is not practical.

308.02

ROADSIDE BARRIER TYPES AND FEATURES

There are two types of roadside barriers commonly used. See Figure 300.08. • •

Blocked-Out W-Beam Barrier Roadside Concrete Barriers

Block-Out W-Beam Barrier - This barrier system is the mainly used as a guardrail system. It shall be installed in most locations that warrants a guardrail system, except for urban areas and locations that require a concrete barrier. This system has been tested to successfully redirect 800-2000 kg vehicles. It has also successfully redirected a 2100 kg van at impact conditions of 21° at 95 kph. Concrete Safety Shape Barrier - The concrete safety shape roadside barrier is a rigid system designed to redirect vehicles without any deflection. Because of its rigidity, vehicles would have a higher probability of overturning or vaulting over the barrier. Therefore, shape of the front face of the barrier is critical to its performance. The distance from the top of the roadway surface to the break between the upper and lower slopes shall not exceed 330 mm. Roadside barriers are also designed with varying heights to counteract overturning moments of trucks with high centers of gravity. The basic roadside barrier is designed at 810 mm high. At this height, the roadside barrier can successfully redirect 820-2000 kg vehicles, and occasionally redirect 18,000 kg buses at moderate impact. A roadside barrier designed at 1070 mm high, have successfully redirected a 36,300 kg tractor-trailer with impact conditions of 15° at 84 kph.

Part 2 300-11


Figure 300.07 Risk Warrants for Embankments

308.03

308.03.01

ROADSIDE BARRIER PLACEMENT

308.03.02

Lateral Placement

Placement of a barrier system shall be determined in a manner that increases motorist safety, decreases accidents and minimizes injuries. A barrier system shall shield the motorist from roadway hazards and not contribute to the hazard. It is therefore a standard rule that the barrier system shall be placed as far from the edge of travelled way as possible. This allows drivers room to regain control of their vehicle and possibly avoid an accident. It is important to note however; as the distance between the edge of travelled way and the barrier increases, the potential angle of impact of the vehicle also increases. Barriers at high angle of impacts are significant hazards themselves.

Barrier to Hazard Clearances

In cases when a roadside barrier is required to shield an isolated hazard, clearance must be provided between the barrier and the hazard. Upon impact, some barriers will deflect, making the clearance between the barrier and the hazard important. Furthermore, if a barrier is struck by a vehicle with a high center of gravity, the vehicle may roll or vault over the barrier. If sufficient distance is not provided, the vehicle may collide with the hazard. Sufficient distance must be provided between the barrier and the hazard being shielded.

Part 2 300-12


Effects of Roadside Terrain

The profile between the edge of traveled way and the barrier can have significant effects on the final placement of the barrier. The vehicle’s wheels should remain in contact with the ground and its suspension system neither compressed or suspended at the moment of impact with the barrier. This holds true for all barrier systems. Locations of roadside curbs and slopes require particular attention when determining barrier design and placement. Curbs - Guardrail/Curb combinations are highly discouraged in locations where high-speed and high angle impacts are likely to occur. Areas with no alternative but to use this combination shall use a curb less than 100 mm or, stiffen the guardrail to reduce deflection by bolting a wbeam to the back of the posts or by adding a rub rail. Slopes - As previously mentioned, guardrail performance is affected by the vehicle’s position at moment of impact. Crash tests show, roadside barriers perform most effectively when installed on slopes 1:10 or flatter. 308.03.04

Barrier Length Design

Runout Lengths (LR) and Hazard Lateral Distance (LH) - When designing the length of a barrier, the two primary factors that must be considered are: • •

LR - Runout Length LH - Hazard Lateral Distance

The runout length (LR) is the distance a vehicle needs to stop prior to colliding with a hazard once it has left the roadway. Its distance is measured from the point the vehicle is assumed to leave the roadway to the hazard ahead. Runout length requirements vary according to the roadway design speed. See Figure 300.04. The lateral distance (LH) is the distance between the edge of the travelled way to the far side of the hazard, if the hazard is a fixed object. If the hazard is an embankment, the lateral distance would be extended to the edge of the clear zone. If the hazard extends beyond the clear zone, the minimum lateral distance would be only to the edge of the clear zone. After determining the runout length and lateral distance, the length of the barrier depends on the barrier tangent length, barrier lateral offset, and flare rate.

Figure 300.08 Roadside Barrier Types and Features Part 2 300-13


Figure 300.09 Barrier Layout Diagram Part 2 300-14

ROADWAY DESIGN MANUAL – Roads and Bridges Barrier Tangent Length (LT) and Barrier Lateral Offset (L1) - The barrier tangent length (LT) is the portion immediately ahead from the hazard and parallel to the roadway. It is of variable length, selected by the designer, and shall be at least as long as the flared section of the barrier.

Median barriers are warranted in locations that have a history of cross-median accidents. On roadways that have wide medians, (greater than nine meters) median barriers generally are not warranted unless there is a history of crossmedian accidents or there are fixed object hazards within the median.

The barrier’s lateral offset (L1) is the distance between the edge of travelled way to the barrier. This offset is also selected by the designer and shall be as far away from the edge of travelled way as possible. This provides an unobstructed recovery area to allow an out of control vehicle to gain control without colliding with the barrier.

308.04.02

Flare Rate (b:a) - The flared portion of the barrier is not parallel to the roadway. Flared sections are used mainly to introduce the barrier toward the barrier line or a narrower segment of the roadway. The flared transition decreases the likelihood that the barrier is perceived as a hazard by motorists. Flared barrier sections have their disadvantages. The greater the flare rate, the greater the angle of impact from an approaching vehicle. This may increase the magnitude of injuries particularly with rigid barriers. Barrier flares can also increase the probability that an impacting vehicle will be redirected across the roadway and into incoming traffic. This is particularly dangerous if the roadway has two-way traffic not separated by a median or a median barrier. Therefore, flatter flare rates shall be used particularly in locations with two-way traffic or steep embankments.

Median Barrier Types and Features

There are three types of commonly used median barriers. See Figure 300.10. • • •

Concrete Safety Shape Median Barrier Single Face Concrete Barrier Metal-Beam Guardrail

The concrete safety shape barrier is the most commonly used median barrier, and shall be installed in most locations requiring a barrier. In areas where the adjoining sections of roadway have previously installed a Metal Beam Guardrail consideration may be given to continue using it for that segment. Single face Concrete Barriers are used mainly to shield hazards or for earth berm support. 308.05

MEDIAN BARRIER PLACEMENT

The two primary factors to consider when placing median barriers are: • •

Median Geometry Treatment of Fixed Object Hazards in the Median

See Figure 300.09 for barrier layout diagram. 308.05.01 308.04 308.04.01

Median Geometry

MEDIAN BARRIERS Median Barrier Warrants

A Median barrier’s primary function is to separate opposing traffic on a divided roadway and/or shield fixed object hazards within the median. Like all types of barriers, median barriers shall only be installed if it is less hazardous colliding with the barrier than not having a barrier installed at all. Barrier installation shall be considered only if the fixed object hazards can not be removed.

As previously mentioned, a median that is flat (1:10 or flatter), relatively smooth and clear of fixed obstacles is desirable. If a median barrier is warranted under these conditions, it shall be installed at the center of the median. If the median is a v-shaped foreslope embankment or a ditch and warrants a barrier, it shall be installed near the shoulder on both sides of the median.

Part 2 300-15

ROADWAY DESIGN MANUAL – Roads and Bridges If the full width of the median is a foreslope embankment steeper than 1:10, and warrants a barrier, the barrier shall be installed on the higher edge of the median. If the slope is 1:10 or flatter and requires a barrier, the barrier shall be installed at the center of the median. However, if the median is rough cut, obstructed with hazards, and non-traversable, barriers shall be installed, at the edge of both shoulders.

308.05.02

In some situations, the entire median does not require a barrier system. However, there may be hazards in the median that require shielding. Treatment of hazards can include but not limited to those illustrated in Figure 300.11. 308.06

If the median is a backslope that is rough cut, non-traversable or is inside the clear zone area, barriers shall be installed on both sides of the median to avoid vehicle snagging. If the backslope is traversable but sufficiently steep to redirect vehicles, a semi rigid barrier can be installed on the high point of the slope.

Treatment of Fixed Object Hazards

308.06.01

END TREATMENTS AND CRASH CUSHIONS End Treatments

All roadside and median barriers terminating within the clear zone and/or are located where they have a high probability of being hit head-on, shall terminate with a crashworthy terminal on the approach end of the barrier. Refer to the most recent edition of the AASHTO Roadside Design Guide.

Figure 300.10 Median Barrier Types and Features

Part 2 300-16


Figure 300.11 Treatment of Fixed Hazards Part 2 300-17


The minimum requirement for a crash cushion system shall have the following characteristics:

Crash Cushion

A Crash Cushion’s main function is to decrease the magnitude of an accident by absorbing some of the force from an impact. They are effective in gradually slowing down and stopping or safely redirecting errant vehicles in head-on and side impact collisions. Crash Cushions shall be used to shield hazardous conditions and fixed object hazards that can not be removed, relocated or designed to breakaway. These include ends of bridge barriers, rails and bridge piers in gore areas. Crash Cushions are also commonly used at ends of roadside and median barriers . Selection Guidelines The selection criteria for crash cushions differ in each individual case. Engineers must evaluate each hazard and select the most effective and appropriate crash cushion system for that case. Refer to the most recent edition of the AASHTO Roadside Design Guide.

•

The system shall be able to stop or redirect a colliding vehicle without any debris penetrating the passenger compartment of the vehicle.

•

The colliding vehicle shall remain in the upright position and not violently redirected to other traffic.

308.06.03

Placement Recommendations

Crash Cushion systems perform best on relatively flat surfaces. Therefore they shall be installed on hard level surfaces such as portland cement concrete or hot bituminous concrete pads. This allows the crash cushion system to compress uniformly throughout the impact. The path between the roadway and the crash cushions shall be relatively smooth and clear of obstructions. Ideally the vehicle’s suspension systems should not be collapsed or extended when it collides with the crash cushions.

Part 2 300-18


SECTION 400 AT-GRADE INTERSECTIONS 401

GENERAL

An intersection is the area where two or more roadways connect. It includes the roadway and roadside facilities available for traffic movement. Each roadway radiating from an intersection is called an intersection leg. Intersection design is very important to the overall roadway safety and level of service. Many accidents and safety problems occur at intersections. Intersection type and spacing control roadway capacity and travel time. Intersections handle a variety of conflicts among vehicles and pedestrians. Vehicles arriving, departing, merging, turning, and crossing traffic have to be accommodated within a relatively small area. These movements may be handled by various means, depending on the intersection type.

There are three categories of roadway intersections. This section deals with at-grade intersections. Grade separations (i.e., without ramps), and interchanges are discussed in Section 500.

402

DESIGN CONSIDERATIONS

Intersection design affects roadway efficiency, safety, capacity, operating cost and operating speed. Well designed intersections reduce the severity of user conflicts while accommodating their varied interests. Intersection design is a cooperative effort between roadway and traffic engineers, based on human factors, traffic considerations, physical elements and economic factors.

403

AT GRADE INTERSECTION TYPES

There are three basic types of at-grade intersections, the three-leg intersection, the fourleg intersection, and the multileg intersection. See Figure 400.01. Factors in determining the type of intersection include, the number of

Figure 400.01 Basic Intersection Types Part 2 400-1

ROADWAY DESIGN MANUAL – Roads and Bridges intersecting legs, topography, traffic patterns, and desired operation. Intersections within a basic type vary greatly however, the general application of at-grade intersection design is common to all. Traffic volume, design speed, and the roadway classification are the principal factors used to determine intersection type. Three-Leg Intersection - The three-leg intersection has three intersecting legs which form a “T” or a “Y”. Operationally three-leg and fourleg intersections are preferred and multidirectional "Y" intersections and intersections with more than four legs should be avoided.

• • • • • • • •

Give preference to major traffic movements. Reduce areas of conflict. Cross traffic at right angles (75-90o desirable - skew no more than 60o.) Separate points of conflict. Provide speed-change lanes and separate turning lanes where appropriate. Restrict undesirable movements. Provide adequate width to shadow turning traffic. Enhance signal control.

404.01

PREFERENCE TO MAJOR MOVEMENTS

Four Leg Intersections - Four-leg intersections may be right angled, oblique, or offset. The rightangled crossing is easily signed and signalized, provides good visibility, and is the safest to negotiate. The oblique crossing creates problems with visibility, pedestrian safety, and vehicleturning angles. The offset intersection has low capacity, is difficult to comprehend and negotiate, and is difficult to sign and signalize.

Whenever possible, preference should be given to the major traffic movements. This usually requires stopping, funneling, or eliminating minor movements. Controlling measures should conform to natural movement paths and be introduced gradually to promote smooth and efficient operation.

Multileg Intersections - These intersections have more than four legs and can have several configurations. Multileg intersections are confusing, have poor visibility, poor turning angles, and are difficult to sign, mark, and signalize. This type of intersection should be avoided if possible.

Large multilane undivided intersection areas are undesirable because drivers cannot predict the other vehicles movements. By separating traffic movements into definite travel paths channelization reduces these conflicts. Channelization also separates points of conflict within the intersection and clearly defines vehicle pathways.

Roundabout Intersections - Roundabout designs generally have three or four legs joining a circular roadway. All traffic turns right to merge with traffic in the roundabout. Traffic continues to turn right through the circle to eliminate through and left turn movements. Roundabout designs are characterized by light traffic volumes and slow speeds through the intersection. The roundabout intersection is a design that can be used in lieu of the traditional three or four leg intersections. For further descriptions and types see Part 2, Section 407, Roundabout Design.

404

CHANNELIZATION

Channelization is the separation of traffic into definite travel paths using pavement markings or raised islands. Channelization should be used to:

404.02

404.03

AREAS OF CONFLICT

INTERSECTION ANGLES

A 90o intersection provides the shortest crossing for intersecting traffic and provides the most favorable condition for drivers to judge the relative position and speed of approaching vehicles. The minimum desirable intersection angle is 75 degrees. Intersection angles less than 60 degrees should be realigned. 404.04

POINTS OF CONFLICT

Points of conflict occur when drivers paths cross. The highest number of conflicts occur at intersections. For example, a driver making a left turn on to a roadway must cross right-bound traffic and merge into the left-bound traffic

Part 2 400-2

ROADWAY DESIGN MANUAL – Roads and Bridges stream. That single maneuver causes conflict with both directions of travel. Where ever possible, points of conflict should be reduced so drivers are only exposed to one conflict or decision at a time. This can be done by using stop signs, traffic signals, grade separations, and channelization. Channelization separates and clearly defines points of conflict within the intersection. Channelization separates and clearly defines points of conflict within the intersection. Drivers should be exposed to only one conflict or confronted with one decision at a time. 404.05

SPEED-CHANGE LANES

Speed-change lanes improve intersection safety and efficiency. Entering traffic merges most efficiently with through traffic when the merging angle is less than 15o and speed differentials are at a minimum. Speed change lanes for diverging traffic should permit vehicles to decelerate after leaving the through lanes.

404.08

Traffic islands may be used to divert traffic streams in desired directions and prevent specific undesirable movements. 404.09

EFFECTIVE SIGNAL CONTROL

At intersections with complex turning movements, channelization is required for effective signal control. Channelization enables sorting and storing of approach traffic for orderly movement through the intersection during separate signal phases. Channelization is particularly effective when used with trafficactuated signal controls. 404.10

INSTALLATION OF TRAFFIC CONTROL DEVICES

Traffic islands enhance the effectiveness of, and provide space for, traffic control devices such as signals and signs. Dimensions and clearances for traffic control devices should be considered when sizing traffic islands. 404.11

404.06

PROHIBITED TURNS

GUIDELINES

TURNING MOVEMENTS •

Striping is preferable to curbed islands, especially adjacent to high-speed traffic where curbing can be an obstruction to outof-control vehicles.

•

Where curbing must be used, first consideration should be given to mountable curbs. Barrier curbs should only be used where pedestrian protection is a primary concern.

Properly sized traffic islands can provide refuge for vehicles and pedestrians. The shadowing effect of islands provides refuge for vehicles waiting to cross or enter an uncontrolled traffic stream.

•

Avoid complex intersections that present multiple movement options or decisions.

•

Accident records provide a valuable guide to the type of channelization needed.

Channelization can also provide a safer crossing of two or more traffic streams by permitting drivers to select adequate gaps in one traffic stream at a time. Channelization should also provide ample storage for vehicles to make the turning or crossing movements.

•

The Standard Drawings include details for a channelized free right turn and typical pavement markings at intersections.

A separate right turning lane removes turning movements from the intersection area, increasing safety and capacity. Also adding dedicated left turn lanes removes left turn traffic from the thru lanes which also increases safety and capacity. Abrupt changes in alignment or sight distance should be avoided. 404.07

REFUGE AREAS

Part 2 400-3


DESIGN VEHICLES OFF TRACKING

A vehicle traveling around a circular curve sweeps a wider path than the width of the vehicle. The difference between the swept width and the vehicle width is called off tracking. On large trucks and buses offtracking can be significant and must be considered in design. 405.02

DESIGN VEHICLES

Intersection geometric design depends on the dimensional and operational characteristics of the vehicles involved. The American Association of State Highway and Transportation Officials have adopted "design vehicles" representing the various classes of commonly used vehicles. For freeways and expressways, the design vehicle shall be a WB-12 medium tractor semi-trailer combination. For arterials, collectors and sector roads, the design vehicle will be a single unit bus. Design vehicles are as defined in “A Policy on Geometric Design of Highways and Streets”, AASHTO, 1994. Dimensions for various design vehicles are shown in Figure 400.02. 405.03

406.01

Unobstructed sight distance along all intersection approaches and across the included corners must be sufficient to permit operators of approaching vehicles to perceive each other, react and complete an appropriate accelerating, slowing or stopping maneuver. If all corners of the intersection cannot be cleared and maintained to provide unobstructed views in the approach sight triangle, the intersection shall have stop control imposed. Departure Sight Triangle - The departure sight triangle is bounded by the location of the stopped driver, the appropriate sight distance along the intersecting road, and the connecting sight line. See Figure 400.04. The driver must have sufficient sight distance along the intersecting legs to make a safe departure movement. All corners of the intersection shall be constructed to provide a clear line of sight throughout the departing sight triangle.

TURNING TEMPLATES

Turning templates are used to locate the turning paths of large vehicles. The template is used to determine corner radii, position island noses, establish clearances and the width of channeled separate turning lanes. Turning templates for the various design vehicles are shown in Figure 400.03. It should be noted that state-of-the-art turning template computer software exists which can be used in-lieu of Figure 400.03.

406

Approach Sight Triangle - The area bounded by the required sight distances along the intersection legs and the sight line connecting their ends is known as the "sight triangle". See Figure 400.04.

Intersection Controls - The following controls apply to at-grade intersections. • • • • •

INTERSECTION DESIGN STANDARDS

No Control - vehicles need sufficient sight distance to adjust their speed. Yield Control - Vehicles on minor roadway yield to vehicles on major roadway. Stop Control - Vehicles on minor roadway stop at major roadway. Signal Control - All legs are controlled by either stop signs or traffic signals. Left-turn Control - Stopped left-turning vehicles on minor roadway must yield to opposing vehicles on major roadway.

SIGHT DISTANCE

General - The Driver of a vehicle should have an unobstructed view of the entire intersection. Stopping sight distance shall be the minimum provided throughout all parts of intersections.

No Control - For a given speed, the approach sight triangle is determined from Figure 400.04 and Table 400.01. Departure sight triangles should be commensurate with those provided at stop controlled intersections.

Part 2 400-4

ROADWAY DESIGN MANUAL – Roads and Bridges Table 400.01 Sight Triangle Distances No Intersection Control Vehicle Speed (kph) Distance (m) 20 20 30 25 40 35 50 40 60 50 70 60 80 65 90 75 100 85 110 90 120 100 The sight triangle dimensions are determined using these distances per Figure 400.04 for No Control. These distances are based on level roadways.

Stop Control - Adequate sight distance must be provided so a driver traveling at the design speed can perceive and safely stop at the stop sign. Once stopped, the driver must have adequate sight distance on the major road to permit safe departure movements. The three basic departure movements are: • •

•

Yield Control - Approach sight triangles should be provided at all intersection corners. Minimum sight distances provided along the legs should be at least stopping sight distance. For departure sight triangles see “Stop Control”.

Part 2 400-5

To travel across the intersecting roadway, clearing oncoming traffic in both directions; To turn left onto the intersecting roadway, clearing oncoming traffic from the left and entering the traffic stream coming from the right; To turn right onto the intersecting roadway by entering the traffic stream coming from the left.


Figure 400.02 Design Vehicle Dimensions

Part 2 400-6

ROADWAY DESIGN MANUAL – Roads and Bridges This turning template shows the turning paths of the specified AASHTO design vehicle. The paths shown are for the left front overhang and the outside rear wheel. The left front wheel follows the circular curve, however, its path is not shown.

Figure 400.03 Minimum Turning Path for P Design Vehicles From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets

Part 2 400-7


FOR APPROACHING VEHICLE

FOR DEPARTING VEHICLE

Figure 400.04 Intersection Sight Triangles Part 2 400-8

ROADWAY DESIGN MANUAL – Roads and Bridges Stop Control with Crossing Maneuver Crossing maneuver sight distance is based on the time it takes for the stopped vehicle to clear the intersection and the distance travelled in that time by an oncoming vehicle on the cross road. The distance may be calculated from d = 0.28V(2.0+ta) where:

d = sight distance required along the major roadway from the intersection (m). V = design speed on the major roadway (kph) ta = time required to accelerate and traverse the distance to clear the major roadway travelled way (s)

The solid line curves in Figure 400.05 labeled “P”, “SU” and “WB-15” are the recommended vehicle time-distance relationships to compute ta. If significant grades are present, ta should be adjusted per Table 400.02. The distance that a crossing vehicle travels to clear a major roadway is: S = D+W+L where:

D = distance from near edge-oftravelled way to the front of a stopped vehicle (typically 3.0 m). W = travelled way width along path of crossing vehicle (m) L = overall length of vehicle (m)

Figure 400.05 Sight Distance at Intersections Acceleration from Stop. From AASHTO, 1004, “A Policy on Geometric Design of Highways and Streets”

Calculated sight distance shall be checked against stopping sight distance. The larger of the distances shall be used.

Part 2 400-9

ROADWAY DESIGN MANUAL – Roads and Bridges Turning Left Onto a Major Roadway Because it takes longer to turn and accelerate to operating speed than to go straight across an intersecting roadway, the critical sight distances are those required for turning movements. The driver must have sufficient sight distance to the left to cross the near lanes(s) without interfering with oncoming traffic. The driver must also have sufficient sight distance to the right to turn left and accelerate to a speed where oncoming traffic is not significantly impaired. The sight distance required to the left are calculated from: dL = 0.28V(2.0+ta) where:

dL = sight distance required to the left along the major roadway from the intersection (m). V = design speed on the major roadway (kph) ta = time required to accelerate and traverse the distance to clear the traffic in the lane approaching from the left.

The required sight distance to the right is based on the assumption that the mainline vehicle will slow to 85 percent of the design speed and maintain a 2.0 second gap from the turning vehicle. To calculate the necessary sight distance first determine from Figure 400.06 the distance P required for the turning vehicle to reach a speed of 85 percent of the mainline design speed. The sight distance required to the right is calculated from:

where:

dR

=

(t+2)(.28)(.95V) - (P-5(.56)(.85V) - Lv)

dR

=

Sight distance required to the right along the major roadway from the intersection (m). time required to travel distance P (Table 400.01). mainline design speed (kph) Vehicle Length (m)

T

=

V

=

Lv

=

requirement for the right-turn maneuver is approximately one meter less than that required for the left-turn maneuver in “Turning Left Onto a Major Roadway”. See Figure 400.07 curve Cb for the required sight distance for a vehicle turning right and accelerating to 85 percent of the design speed before being overtaken by vehicles slowing to 85 percent of design speed. Trucks will take considerably longer than passenger vehicles. Signal Control - Because of unanticipated vehicle conflicts at signalized intersections, (such as, signal violations, right-turns on red, signal malfunction, or use of flashing red/yellow mode) the requirements for Stop Controlled intersections should be met. At intersections where right-turns on red are permitted, the departure sight line for right-turning vehicles should be determined by the methods for “Turning Right into a Major Roadway." Stopped Vehicle Turning Left from a Major Roadway - The driver will need sufficient sight distance ahead to turn left and clear the opposing travel lane(s) before an approaching vehicle reaches the intersection. The sight distance required is calculated from: d = 0.28V(2.0+ta) where:

d = sight distance required along the major roadway from the intersection (m). V = design speed on the major roadway (kph) ta = time required to accelerate and traverse the distance to clear the traffic in the approaching lane.

406.02

EFFECT OF SKEW

Intersection skew has no effect on sight distance requirements since they are measured along the intersecting legs. However, the sight triangle configuration is affected by skew. Care should be taken to verify that the area within the sight triangles can be constructed and maintained to provide a unobstructed view throughout the sight triangle with a 1070 mm eye height on the minor road to a 1300 mm object height on the major road.

Turning Right Onto a Major Roadway - The right-turning-vehicle must have sufficient sight distance to the left to complete its turn and accelerate to a predetermined speed before being Skew also affects the distance a vehicle travels to overtaken by approaching traffic travelling at the cross the intersection. Heavily skewed same predetermined speed. The sight distance intersections should be controlled. Part 2 400-10


Figure 400.06 Acceleration Curves From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets” Part 2 400-11


Figure 400.07 Intersection Sight Distances For turning onto a major roadway AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets” Part 2 400-12


EFFECT OF VERTICAL PROFILES

A vehicle descending a grade requires greater stopping distance than one on level ground. Conversely, a vehicle ascending a grade requires less distance to stop. Grades up to 3 percent have little effect on stopping sight distances. In no case should the grades exceed 6 percent. For Stop Controlled intersections, the time required to cross a roadway is affected by the crossing grade. If the grade is significant, the sight distance should be increased. Where the intersection leg grades are other than flat, corrections should be made to the sight distances using the approximate ratios given in Table 400.02. Table 400.02 ta Adjustment For Grade Sight Triangle Distances Ratio, ta on grade / ta level (Figure 400.05)

be 3.65 m. Three meter wide left-turn lanes may be used on low speed urban roadways. The width is measured from the adjacent edge of travelled way, excluding shy distance. Medians - To improve left-turn visibility, the leftturn-lane should be placed as far to the left as possible in the median leaving only the painted or curbed nose. Excess width between the left-turn lane and the adjacent same-direction through lane should be treated as painted island. When leftturn lanes are placed in raised (curbed) medians, a minimum nose width of 1.0 m should remain for pedestrian refuge and traffic control devices. Approach Tapers - On roadways with narrow or no medians, room for the left-turn lane is made by shifting traffic laterally to the right. The taper length used to effect this shift should be 0.6WV, where W = lateral shift (m) and V = design speed (kph). Bay Tapers - The bay taper length should be short to clearly identify the additional lane. Generally the taper length should be 15:1.

Crossroad Grade % Design Vehicle P SU WB-15

-4 0.7 0.8 0.8

-2 0.9 0.9 0.9

0 1.0 1.0 1.0

2 1.1 1.1 1.2

4 1.3 1.3 1.7

Use this table to adjust ta values for effect of grade. Based on the likely range of crossing distances. 406.04

LEFT-TURN CHANNELIZATION

Deceleration Length - Whenever feasible, the left-turn lane should provide deceleration clear of the through lanes. The minimum deceleration lengths, exclusive of bay taper and vehicle storage, for 50, 60 and 80 kph are 70, 100 and 130 m, respectively. In urban areas, it may not be possible to provide the deceleration lengths and maintain the storage and approach taper lengths required. In these situations, these lengths should be used as a desirable goal.

General - A left-turn lane expedites through traffic flow, controls turning traffic movement, and improves the intersection safety and capacity.

Storage Length - The storage length should be sufficient:

The left-turn lane should be laid out such that the turning vehicle must make a definite move to enter the lane. The desirable length of the left-turn lane is the sum of the required storage length and deceleration length, including the bay taper length.

•

Width - The desirable left-turn lane width should

•

•

To store the number of vehicles during critical periods. To avoid left-turning vehicles stopping in the through lanes. So the lane entrance is not blocked by standing through traffic.

Refer to the “Highway Capacity Manual, Special Report No. 209”, Transportation Research Board, 1986 for further discussion.

Part 2 400-13


RIGHT-TURN CHANNELIZATION

Storage Length - Storage requirements and goals are the same as for left-turns.

General - Right-turn lanes improve intersection capacity and safety. As for left-turn lanes, rightturn lanes should be laid out such that a rightturning vehicle must make a definite move to enter the lane. The desirable length of the right-turn lane is the sum of storage requirements and deceleration length, including bay taper.

Free Right-Turns - Uncontrolled “free” rightturns improve capacity of an intersection with a heavy right-turn demand. The right-turn is made "free" by channelizing the turning movement outside of the intersection controls. Free rightturns shall only be provided where the turning movement can be made into an auxiliary or acceleration lane. 406.06

Width - The desirable right-turn lane width should be 3.65 m. Three meter wide right-turn lanes may be used on low speed urban roadways. The width is measured from the adjacent edge of travelled way, excluding shy distance.

General - Traffic islands are located between traffic lanes and are commonly designated using paint, raised pavement markers, or curbs. They serve to:

The normal shoulder should be provided at the right-turn lane although, if right of way is severely constrained, a minimum 1.2 m wide shoulder may be used. The normal curb should be carried through the right-turn section.

•

Approach Tapers - Generally right-turn lane approach tapers are not required because the lane is added to the outside of the travelled way and the travel lanes are not shifted. However, if the travel lanes must be shifted to accommodate a right-turn lane, the taper should be the same as for left-turn lanes.

•

Bay Tapers - The bay taper which guides the motorist into the right-turn lane is a straight line along the right edge of the travelled way. Generally the taper length should be 15:1. Deceleration Length - Whenever feasible, the right-turn lane should provide deceleration clear of the through lanes. The minimum deceleration lengths, exclusive of bay taper and vehicle storage, for 50, 60 and 80 kph are 70, 100 and 130 m, respectively. In urban areas, it may not be possible to provide the deceleration lengths and maintain the storage and approach taper lengths required. In these situations, these lengths should be used as a desirable goal.

TRAFFIC ISLANDS

• •

confine specific traffic movements into definite channels; separate traffic moving in the same or opposite direction; aid and protect pedestrians crossing the intersection; and, discourage or prohibit undesirable movements.

Design - Traffic islands must be large enough to be seen and to command the attention of the driver. Islands for channelizing should preferably be at least 9.0 m2. Curbed islands for separating traffic streams should not be less than 1.0 m wide and 8.0 m long. Curbed islands should be offset from the through traffic lanes by a minimum shy distance of 0.6 m and 0.9 m is preferable for approach speeds greater than 25 kph. The approach end of a curbed island should be rounded at 0.5 to 1.0 m radius and tapered at 15:1 to guide the driver into the channelization. Where there is an approach shoulder (1.2 m or wider), the curbed island should be offset from the through lane by the width of the shoulder. With an approach shoulder the flared approach is not necessary, except where a deceleration or turning lane has been provided.

Part 2 400-14

ROADWAY DESIGN MANUAL – Roads and Bridges Avoid curbed traffic islands where the approach operating speeds are 80 kph or greater. Mountable curbs should be used at curbed islands except where barrier curbs are provided for greater pedestrian protection.

•

407

•

ROUNDABOUT DESIGN

There are three main types of roundabouts, Normal, Mini and Double. There are other forms of roundabouts but they variations of these basic types. They are Ring Junctions, Grade Separated and Signalized Roundabouts. More information about the use and design of these and other roundabouts can be found in the Geometric Design of Roundabouts. When reading this design manual the designer should be aware that the manual was written for left-hand running traffic and appropriate modifications should be made for when adapting these standards to righthand running traffic patterns. The roundabout is used at intersecting streets with low capacity and low design speed. Roundabouts should be considered when they are cost effective or increase safety over standard intersection designs.

roundabout. For these reasons roundabouts tend to be removed and replaced with conventional signalized intersections instead of being modified. Roundabouts require more land than conventional intersections. Roundabouts are not well suited for pedestrian traffic, because pedestrians are not able to walk in a clear path through the intersection. In areas of high pedestrian traffic, pedestrians can cause major problems with illegal crossings.

Normal Roundabouts: The normal configuration of a roundabout is made up of a one-way road around a circular curbed island 4m or more in diameter. The approaches are usually flared to allow multiple vehicle entries. The number of entries should be limited to three or four arms. The efficiency and driver comprehension decreases as the number of arms is increased. The minimum radius of curvature also increases with additional arms which can raise circulatory speeds. Double roundabouts can be an alternative under these conditions. See Figure 400.08.

Advantages: There are several advantages to roundabout design versus conventional three and four leg intersections. • Roundabouts are more efficient than signals on balanced traffic demand intersections. • Roundabouts allow for continuous traffic flow. • Roundabouts can reduce traffic speeds in existing intersections. Disadvantages: There are several disadvantages to roundabouts that make them less favorable than conventional designs. • Driver comprehension to right-of-way with respect to yielding to traffic flow. • Roundabouts are prone to large congestion problems when traffic exceeds design capacity. • It is difficult to redesign an existing roundabout to increase its capacity. Redesign requires adding more lanes which greatly increases the land required for the intersection. This increase in diameter also increases the design speed through the

Figure 400.08 Normal Roundabout Mini Roundabouts: The mini-roundabout is similar to the normal roundabout except the diameter of the island is less than 4m. Instead of a curbed island a raised, reflectorized dome is used for driver recognition of the high spot. The mini-roundabout is a good alternative for existing roads with extremely low traffic volumes that have high safety and delay problems. Where physical deflection of approaching traffic is not

Part 2 400-15

ROADWAY DESIGN MANUAL – Roads and Bridges possible, roadway stripping and traffic islands may be used. See Figure 400.09.

Figure 400.10 Double Roundabout

Figure 400.09 Mini Roundabout

Double Roundabouts: Double roundabouts are generally used in areas with unique traffic requirements such as: • Where intersection improvements are done and the roundabout eliminates the need to realign an approach road. • In areas where more than four arms are entering the intersection. • At intersections with unusual or asymmetrical configurations. • Where single island configurations do not have enough capacity. • The joining of parallel roads separated by an existing feature. These unique circumstances should be evaluated by an experienced traffic engineer and the Municipality must be informed on the decision to consider a double roundabout. The double roundabout should only be used after proper consideration and is contingent only with the approval of experienced personnel and the Municipality. See Figure 400.10.

Part 2 400-16


SECTION 500 INTERCHANGES

503 DESIGN CONSIDERATIONS

501 GENERAL The ability to accommodate high traffic volumes safely and efficiently through intersections depends on how intersecting traffic is handled. The greatest efficiency, safety, and capacity are attained when intersecting through traffic lanes are physically separated. An interchange does this with a combination of ramps and grade separations at the junction of two or more roadways. This reduces or eliminates traffic conflicts, improves safety, and increases traffic capacity. Crossing conflicts are eliminated by grade separations and turning conflicts are eliminated or minimized depending on the interchange configuration. The selection and design of grade separations and interchanges is influenced by roadway classification, traffic volume, traffic composition, design speed, access control, signing requirements, economics, terrain, right-of-way, capacity and safety. Interchange types vary widely so each site should be studied and alternate concepts made to determine the appropriate layout.

Due to the complex nature of interchange design it is important to establish a set of consistent design parameters. Listed below are features which should be considered during the interchange design process. • • • • • • • •

Provide consistent design features. Ramp exits shall be from the right. Ramp entrances shall be on the right. One exit per direction from main roadway. Ramp design speed beyond exit should preferably be one-half to two-thirds that of the roadway. Provide ramps for return or complementary traffic movements at same interchange. Use grades and slopes as flat as possible. Consider signing during geometric design.

504 INTERCHANGE TYPES This section includes examples of commonly used interchange configurations. See Chapter X of "A Policy on Geometric Design of Highways and Streets," AASHTO, 1994, for additional examples. 504.01 THREE-LEG INTERCHANGE

502 INTERCHANGE WARRANTS Interchanges are very costly and should be used only where necessary. Interchanges should be considered based on the following warrants: • • • • • • •

Where intersecting traffic volumes are heavy. Where topography does not lend itself to the construction of an intersection. When making a connection to a freeway. For a roadway with access control between selected terminals. To eliminate a traffic bottleneck. To eliminate a hazardous at-grade intersection. When road-user benefits are substantial.

Three-leg interchanges have three intersecting legs. They usually consist of one or more roadway grade separations and one-way roadways for all traffic movements. Because future expansion is difficult, three-leg interchanges should only be used when one of the three legs is permanently terminated. Heavy traffic volume should be favored with more direct alignments, and lesser volumes can be looped. Skewed crossings are desirable because travel distance is less, the turning radius is flatter for the heavier left-turning volume and there is less angle of turn for both left turns. Figure 500.01 illustrates several types of three leg interchanges.

Part 2 500-1


Figure -500.01 Three-Leg Interchanges From AASHTO, 1994," A Policy on Geometric Design of Highways and Streets".

Part 2 500-2


FOUR-LEG INTERCHANGES

Four-leg interchanges include diamond interchanges, full cloverleaves, partial cloverleaves (parclo), and interchanges with direct and semidirect connections. Each basic interchange type is described and discussed in the following sections. Diamond Interchange Diamond interchanges are the most commonly used interchange (Figure 500.02). They consist of four ramps which parallel the main roadway, providing all eight turning movements.

• • • • •

Comparatively low construction cost. Direct cross road turning maneuvers. Single exit feature simplifies expressway signing. No need for speed change lanes on or under the structure. No weaving on the expressway.

Disadvantages • Overall capacity is limited by ramp intersection capacity. • Capacity is lowered on the minor road due to left turning movements. • Increased accident potential unless signalized. • Possibility of wrong-way movements. • Turning traffic from the expressway is obliged to stop at the minor road. Storage lane treatment may be required. • Little possibility for future expansion. Single Point Diamond Interchange The Single Point Interchange (SPI) is also known as an urban interchange or a single point diamond interchange (Figure 500.03). All four turning movements are controlled by a single traffic signal and opposing left turns cross to the left of each other.

Figure 500.02 Simple Diamond

Application - The diamond is used at major/minor roadway crossings with direct high speed exit/entrance ramps on the major roadway and at-grade intersections on the minor roadway. It is adaptable to a wide range of traffic volumes and capacity may be increased by widening the ramps and cross road in the intersection area by providing storage lanes, two-lane left turns, channelization, and traffic signals at the ramp cross road intersections. Advantages • High design standard single exits in advance of the structure. • High design standard single entrances beyond the structure. • Requires relatively little right-of-way. Part 2 500-3

Figure 500.03 Single Point Diamond Interchange

ROADWAY DESIGN MANUAL – Roads and Bridges Application - Best suited for areas where rightof-way is restricted. Advantages • Relatively narrow right-of-way. • Opposing left turns pass to the left of each other. • Traffic signal is three-phase rather than four. • Operates with a single traffic signal reducing delay through the ramp intersection. • Handles high volume left-turns on the cross road more efficiently than a diamond. • Curve radii for left-turn movements through the intersection are significantly flatter than at conventional intersections, and therefore the left turns move at higher speeds. • Higher capacity than a conventional tight diamond interchange. Disadvantages • Higher construction cost than a conventional tight diamond interchange. • Extensive retaining walls required where right-of-way is restricted. • Vehicle path through the intersection requires, at a minimum, a painted guidance stripe. • Not suitable for skewed interchanges. • Adding pedestrian movement to the interchange adds a signal phase and reduces efficiency. Cloverleaf The cloverleaf is a four-leg interchange that uses loop ramps to eliminate the four left-turn movements and uses outer ramps for the four right-turn movements (Figure 500.04). An interchange with loops in all quadrants is referred to as "full cloverleaf" and all others as a "partial cloverleaf (parclo)". Application - Where there is a need to avoid restrictive at-grade left turns and adequate right of way is available.

Figure 500.04 Cloverleaf

Advantages • Left-turn conflicts eliminated • Single structure design. • Traffic signals are unnecessary. • Lends itself to stage construction. Disadvantages • Large right-of-way requirements. • Weaving may severely limit capacity. • Adding weaving lanes on and under structure increase cost. • High weave volumes require collector distributor roads. • Double exit on the expressway complicates signing. • Insufficient deceleration length from expressway speed to control speed of inner loop. • Poor safety features. • Extra travel distance/time required for left turns. • Large trucks may experience problems with tight curves.

Part 2 500-4

ROADWAY DESIGN MANUAL – Roads and Bridges Cloverleaf with Collector Distributor Road A collector distributor road in conjunction with a cloverleaf removes the weaving ramp traffic from the main roadway (Figure 500.05).

Disadvantages • May require more right of way than basic cloverleaf. • Higher structure costs than basic cloverleaf due to greater span. • Signing is more complicated than basic clover leaf Partial Cloverleaf (Parclo) A partial clover leaf is a portion of the full clover leaf design. Ramps should be arranged so that the entrance and exit turning movements create the least impediment to major roadway traffic flows. The general parclo interchange applications, advantages and disadvantages are given below. Figures 500.06 through 500.10 show several parclo arrangements and lists their relative advantages and disadvantages. Application - This interchange is suitable for locations where by removing two left-turn movements from the intersections the remaining left-turn conflicts can be tolerated.

Figure 500.05 Cloverleaf with Collector Distributor Road

Application - Same as for basic cloverleaf except is more suitable for areas with high weaving volumes. Advantages • Minimizes weaving conflicts by placing weave on collector distributor road. • Minimizes signing difficulties. • Provides a single exit and entrance from main roadway. • Reduce merging and diverging points on main roadway. • Higher volume than basic cloverleaf design.

General Advantages • Suitable for stage construction. • Exit terminals in advance of structure. • Weaving eliminated. • Single exit simplifies signing. • Expandable if structure opening wide enough. • Can be configured to optimize traffic volume/capacity. • Future expansion if structure opening wide enough. General Disadvantages • Minor road has stop condition for left-turn. • Minor road may require left-turn storage. • Points of conflict on the minor roadway at the ramp terminals limit capacity and safety. • Right-turn expressway traffic stops at minor roadway.

Part 2 500-5


Figure 500.06

Figure 500.09

Advantages • Entrance ramp loops. Disadvantages • Stop condition on minor road and ramps for left turns.

Disadvantages • Stop condition on minor road and ramps for left turns. • Expressway traffic exits onto small radius loop.

Figure 500.07

Figure 500.10

Advantages • Stop for left-turns confined to movements from ramps only. • Entrance ramp loops.

Advantages • Stop condition for left turns confined to movements from minor roadway only. • Not conducive to wrong-way movements. Disadvantages • Expressway traffic exits onto small radius loop. Directional Interchanges

Figure 500.08 Disadvantages • Stop condition on minor road and ramps for left turns. • Expressway traffic exits onto small radius loop. • Entrance/exit loops

A direct connection is defined as a one-way roadway that does not deviate greatly from -the intended direction of travel. Interchanges that use direct connections for the major left-turn movements are termed directional interchanges (Figure 500.11). Direct connections for one or all left-turn movements would qualify an interchange to be termed directional even if the minor left turn movements are accommodated on loops.

Part 2 500-6


Directional interchanges have one or more grade separations with direct or semidirect ramp connections for one or more left turning movements. Free flow is provided for high turning traffic volumes in one or two quadrants comparable in volume to through traffic. When one or more interchange connections are indirect in alignment yet more direct than loops, the interchange is described as semi-directional. All left-turn connections or only those that accommodate major left-turn movements may be semi-direct in alignment. The most widely used type of directional interchange is the four-level layout system shown in Figure 500.11A. A variation of this type is the four-level interchange with two exits from both major roadways, as shown in Figure 500.11B. Chapter X of "A Policy on Geometric Design of Highways and Streets," AASHTO, 1994, has additional examples of directional interchanges. Application - Semi-direct or direct connections for one or more left-turning movements are often required at major interchanges in urban areas. Interchanges involving two freeways nearly always call for directional layouts. In such cases turning movements in one or two quadrants often are comparable in volume to through movements. Advantages • Reduced travel distance. • Increased speed and capacity. • Weaving eliminated. • Avoids the indirection in driving on a loop. • Higher levels of service . • Require little right of way.

Figure 500.11 Directional Interchanges Disadvantages • High construction costs. • Require detailed, time-consuming study.

Part 2 500-7


505

consistent with the design speed for the roadways and driving conditions expected.

INTERCHANGE DESIGN PROCEDURES

General - Since interchanges are so costly, and a vital element of freeway capacity it is important that a well functioning, economic design be conceived. In general, alternative interchange schemes should be analyzed and several preferred alternatives should be selected based on geometry, capacity, signing, aesthetics, environmental compatibility, overall adaptability, route continuity, route uniformity, maintaining traffic during construction, suitability to stage construction, right-of-way requirements and the effect on the local road and roadway network. From these preferred alternatives, preliminary plans, profiles and cost estimates should be prepared. Include costs for right-of way, construction, maintenance, and other appropriate items. Once this data has been prepared, the best interchange design concept can be selected.

506

INTERCHANGE DESIGN STANDARDS

An interchange consists of the through freeway, the ramps and the cross road. This section deals primarily with the interchange as a whole. Specific designs for ramps are discussed in the sections that follow. Sight Distance - Stopping sight distance shall be the minimum sight distance provided on the respective roadways through an interchange and preferably longer. Decision sight distance shall be provided at exits. Sight distance requirements are discussed in Part 2, Section 300, Geometric Cross Section. For minimum radius curves, the normal lateral clearance may not provide minimum stopping sight distance because piers, abutments and bridge rail limit horizontal sight distance. If a flatter curve cannot be used, the clearances should be increased to obtain the proper sight distance even though it is necessary to increase structure spans or widths. Design Speed Considerations - In the design of interchanges it is important to provide vertical and horizontal alignment standards which are

Spacing - Minimum interchange spacing is determined by weaving volumes, ability to sign, signal progression, and required lengths of speed change lanes. Interchange spacing has a pronounced effect on freeway operation. In general, minimum spacing shall be: Rural 3.0 km

Urban 1.5 km

Uniformity - To the extent practicable all interchanges along a freeway should be uniform in geometric layout and general appearance. All entrance and exit ramps shall be on the right. Signing and Marking - Signs, pavement striping, delineators and other markings should conform to the Manual on Uniform Traffic Control Devices (MUTCD). Basic Number of Lanes - Design traffic volumes and a capacity analysis should be used to determine the basic number of roadway lanes and the minimum number of ramp lanes. The basic number of lanes should be established for a substantial length of freeway and should not be changed through pairs of interchanges. Auxiliary Lanes - An auxiliary lane is defined as the portion of the roadway adjoining the travelled way for emergency stopping, speed change, turning, turning storage, weaving, truck climbing, and other purposes supplementary to through-traffic movement. An auxiliary lane may be needed when: • interchanges are closely spaced. • the distance between the end of the taper on the entrance terminal and the beginning of the taper on the exit terminal is short. • local frontage roads do not exist. • necessary for lane balance. • necessary for capacity requirements. • necessary for weaving. An auxiliary lane may be introduced as a single exclusive lane or in conjunction with a two-lane entrance. Auxiliary lanes may be dropped in a single or two-lane exit or carried to the physical gore nose before tapering into the through

Part 2 500-8

ROADWAY DESIGN MANUAL – Roads and Bridges roadway. Auxiliary lanes may be tapered or parallel and shall be a minimum of 3.65 m wide.

Table 500.01 Ramp Entrance/Exit Design Speed

Lane Reduction - The basic number of freeway lanes may be reduced if the exit volume is large enough to change the basic number of lanes required beyond the reduction point for the freeway as a whole.

Freeway Design Speed kph 140 120 100

The reduction may be made at a two-lane exit ramp or between interchanges. The lane-drop taper should be on a horizontal tangent on the approach side of a crest vertical curve, or on a sag vertical curve. The lane reduction shall be made on the right using a desirable taper rate of 70:1 (minimum taper rate of 50:1).

These speeds do not apply to ramp terminals, which should be designed using the intersecting roadway speed.

Weaving Sections - Weaving sections are roadway segments where vehicles entering and leaving at adjacent access points cross each others paths. Weaving sections reduce interchange capacity and should be eliminated from the main facility where feasible. Refer to the Highway Capacity Manual for further discussion on weaving sections.

507 RAMP DESIGN STANDARDS

Profile - A typical ramp profile consists of the ramp body on an appreciable grade, between vertical curves that connect to the intersection legs. The profile at the ramp terminal is generally determined by the cross road. Ramp grades should be as flat as feasible. Down grades should be limited to 3 or 4 percent on ramps with sharp horizontal curvature and significant heavy truck or bus traffic. However, sight distance is more important than a specific gradient control and should be favored in design. As general criteria, it is desirable that ascending gradients on ramps be limited to:

General - A ramp is typically a one-way roadway connecting interchange legs. Ramps consist of three main parts. The ramp freeway entrance or exit, the ramp body and the ramp intersection with the cross road. The intersection with the freeway is called the ramp entrance or exit and the intersection with the cross roads is typically defined as the ramp terminal. This section deals mainly with general ramp design criteria. Specific ramp entrance/exit and terminal designs are discussed separately in the following sections. Design Speed - Ramp design speed varies based on location along the ramp. The freeway entrance or exit design speed approximates the freeway design speed. The ramp terminal design speed usually approximates that of the cross road if there is no stop condition. The design speed for the ramp body transitions from the freeway design speed to the terminal design speed. See typical examples in Table 500.01.

Ramp Design Speed kph 100 85 70

Table 500.02 Ramp Grades Ramp Design Speed kph 70-80 60 40-50 30-40

Ramp Gradient % 3-5 4-6 5-7 6-8

Curvature - The factors and assumptions of minimum-turning roadway curves for various speeds apply to ramps and are discussed in Section 200. Sight Distance - The minimum sight distance provided anywhere along the ramp shall be stopping sight distance. See the sections on freeway entrance/exit ramp and ramp terminals for specific requirements at those areas. Shoulder Width - Shoulder widths for ramps shall be as indicated in Part 2, Section 300, Geometric Cross Section.

Part 2 500-9

ROADWAY DESIGN MANUAL – Roads and Bridges Gores - The term "gore" indicates an area downstream from the shoulder intersection points as illustrated in Figure 500.12. The gore nose is defined as that point where the distance measured between the main line and ramp travelled ways is 7.0 m. If feasible, the unpaved area beyond the nose should be graded level with the roadways. Heavy sign supports, street lights, and roadway structure supports shall be kept out of the graded gore area. Profile grade considerations are of particular concern through entrance and exit gore areas. In some instances the ramp profile, or the combination of profile and cross slope, is sufficiently different from the freeway through lanes that grade breaks across the gore become necessary. Where adjacent lanes or lanes and gore areas at freeway entrances and exits are not in the same plane, the algebraic difference in pavement cross slope shall not exceed 5%.

Lane Drops - Typically the ramp lane reduction shall be made using a desirable taper rate of 70:1, 50:1 maximum. Lane drop tapers should not extend beyond the 2 meter point (the beginning of the weaving length) without the provision of an auxiliary lane. Lane Additions - Lane additions to ramps shall use a taper rate of 10:1. Superelevation And Cross Slope - The factors controlling superelevation rates discussed in Part 2, Section 200, Geometric Design Standards, apply to ramps. Ramp superelevation rates shall be per Table 200.04. Where feasible, the curve radius should be increased to reduce the required standard superelevation rate. Both the edge of travelled way and the edge of shoulder should be examined at ramp junctions to assure a smooth transition.

Figure 500.12 Typical Gore Area From AASHTO, 1994, “A Policy on Geometric Design of Highways and Streets” Part 2 500-10

ROADWAY DESIGN MANUAL – Roads and Bridges Widening - Where ramps have curve radii of 90 m or less with a central angle greater than 60 degrees the lane furthest to the right of the ramp, shall be widened in accordance with Table 500.03 in order to accommodate large truck wheel paths. More than one lane may be widened if warranted by truck and bus usage. Table 500.03 Ramp Widening For Trucks Ramp Radius (m) <40 40 - 44 45 - 54 55 - 64 65 - 74 75 - 90 >90

Widening (m) 2.0 1.6 1.3 0.9 0.6 0.3 0

Lane Width (m) 5.6 5.2 4.9 4.5 4.2 3.9 3.6

For ramps having curve radii of 90 m or less with a central angle greater than 60 degrees. Normally, loop ramps are one lane unless capacity warrants additional lanes. Consideration should be given to providing a directional ramp when loop volumes exceed 1500 vehicles per hour. If multiple lanes are provided, normally only the right lane needs to be widened. Loop Ramps - Radii for loop ramps should normally range from 45 m to 60 m. Increasing the radii beyond 60 m is typically not cost effective as the slight increase in design speed is usually outweighed by the increased right of way requirements and the increased travel distance. For roadway design speeds greater than 80 kph the loop design speed should not be less than 40 kph (45 m radius). Extremely tight curves (less than 35 m radii) should be avoided because they lead to increased off-tracking and increase the potential for vehicles to enter the curve with excessive speed. See Table 200.05 for further guidelines on radius versus design speed. Research indicates that trucks often enter loops with excessive speed, either due to inadequate deceleration on exit ramps or due to driver efforts to maintain speed on entrance ramps to

facilitate acceleration and merging. Where the loop ramp has a small radius on a steep descent (over 6%), it is important to develop the standard 2/3 full superelevation rate by the beginning of the curve. On loop entrance ramps this can often be facilitated by beginning the ramp with a short tangent (20 m to 30 m) that diverges from the cross street at an angle of 4 to 9 degrees. Longer tangents are desirable. Distance Between Successive On-Ramps - The minimum distance between two successive freeway on-ramps should be the distance needed to provide the standard on-ramp acceleration taper shown on Figure 500.13. This distance should be about 300 m. If the upstream ramp adds an auxiliary lane, the downstream ramp should merge with the auxiliary lane. The distance between on-ramp noses will then be controlled by interchange geometry. Distance Between Successive Exits - The minimum distance between successive exit ramps for guide signing should be 300 m on the freeway and 180 m on collector-distributor roads.

508

ENTRANCE/ EXIT RAMP DESIGN STANDARDS

General - The ramp entrance/exit is that ramp portion adjacent to the through travelled way, including speed-change lanes, tapers, and islands. All freeway entrances and exits shall connect to the right of through traffic. The following paragraphs discuss various design elements of ramp entrances/exits. Entrance/Exit Sight Distance - Decision sight distance is desirable along the freeway prior to an exit nose and the entire exit terminal should be visible. When an exit must be located where visibility is limited by physical restrictions which cannot be corrected by cut widening or object removal, an auxiliary lane in advance of the exit should be provided. The minimum length of auxiliary lane shall be 300 m desirable, 180 m minimum.

Part 2 500-11


Figure 500.13 Single Lane Freeway Entrances and Exits From Caltrans, 1995, Highway Design Manual Part 2 500-12

ROADWAY DESIGN MANUAL – Roads and Bridges Exit Design Speed - The minimum design speed at the exit nose should be 80 kph or greater for both ramps and branch connections. Decision sight distance should be provided at freeway exits and branch connectors. Entrance Design Speed - The design speed at the nose should be consistent with approach alignment standards. If the approach is a branch connection or diamond ramp with high alignment standards, the minimum design speed should be 80 kph. Entrance/Exit Designs - Design of freeway entrances and exits should conform to the standard designs in Figures 500.13, 500.14, and 500.15 for single lane, two lane entrances and exits, and diverging branch connections, respectively. A branch connection is defined as a multilane connection between two freeways. The minimum deceleration length shown on Figure 500.13 shall be provided prior to the first curve beyond the exit nose. This provides for adequate deceleration before entering the curve. When the subsequent curve is a descending loop or hook ramp, or if the upstream condition is a sustained downgrade, deceleration length should be increased. (see AASHTO, “A Policy on Geometric Design of Highways and Streets”, 1994, Chap. X for additional information). Single-lane Freeway to Freeway Connections Freeway-to-freeway connectors may be single lane or multilane. Where design year volume is between 900 and 1500 equivalent passenger cars per hour, initial construction should provide a single lane connection with the capability of adding an additional lane. Single lane directional connectors should be designed using the general configurations shown on Figure 500.13, but utilizing the flatter diverge angle shown in Figure 500.15. Single lane loop connectors may use a diverge angle of as much as that shown on Figure 500.13 for ramps, if necessary. The choice will depend upon interchange configuration and driver expectancy. Single-lane connectors in excess of 300 m in length should be widened to two lanes to provide for passing maneuvers.

Two-Lane Exit Ramps - Where design year estimated volumes exceed 1500 equivalent passenger cars per hour, a 2-lane exit per Figure 500.14 should be used. A minimum 400 m auxiliary lane should be provided in advance of a two-lane exit. Provisions should also be made for widening to three or more lanes at the cross road intersection. For volumes less than 1500 but more than 900, a one-lane width exit ramp should be provided with provision for adding an auxiliary lane and an additional lane on the ramp. Branch Connections - A branch connection should be provided when the design year volume exceeds 1500 equivalent passenger cars per hour. Merging branch connections should be designed as shown in Figure 500.14. Diverging branch connections should be designed as shown in Figure 500.15. The standard ramp exit connects to a local street. The diverging branch connection connects to another freeway and has a flatter angle that allows a higher departure speed. At a branch merge, an 800 m length of auxiliary lane should be provided beyond the merge of one lane of the inlet, except where it does not appear that capacity on the freeway will be reached until five or more years after the 20 year design period. In this case the length of auxiliary lane should be a minimum of 300 m. For diverging connections where less than capacity conditions beyond the design year are anticipated, the length of auxiliary lane in advance of the exit should be 400 m. Branch Lane Drops - The lane drop taper on a freeway-to-freeway connector shall not be less than 70:1.

Part 2 500-13


Figure 500.14 Two-Lane Entrance and Exit Ramps From Caltrans, 1995, Highway Design Manual Part 2 500-14


Figure 500.15 Diverging Branch Connections From Caltrans, 1995, Highway Design Manual Part 2 500-15

ROADWAY DESIGN MANUAL – Roads and Bridges Two-Lane Entrance Ramps - A standard two lane entrance ramp is illustrated in Figure 500.14. This design may be utilized in situations where the estimated design year volume exceeds 1500 equivalent passenger cars per hour. Figure 500.14 includes a minimum 300 m auxiliary lane parallel to the freeway, which is only used where adequate design year capacity exists on the through facility. If capacity is inadequate, consideration should be given to extending the auxiliary lane to the next interchange or adding additional freeway through lanes. For most urban situations, it is recommended that multiple ramp lanes taper to a single lane prior to the 2meter separation point (where merging is considered to begin). Entrance/Exit Locations - Freeway entrances and exits should be located on tangent sections wherever possible. This provides maximum sight distance and optimum traffic operation. Where it is necessary to locate entrances/exits on a curve, the ramp entrances and exit tapers should also be curved. The exit taper radius should approximate the freeway edge of travelled way in order to develop the standard degree of divergence (Figure 500.16).

On curved entrance ramps the distance from the inlet nose (4.25 m point) to the end of the acceleration lane taper should equal the sum of the distances shown on Figure 500.13 The 50:1 taper may be curved to fit the conditions, and the 1000 m radius curve may be adjusted. Entrance/ Exit Grades - Grades for freeway entrances and exits are controlled primarily by sight distance requirements. Ramp profile grades should not exceed 6%. Exit Profiles - Vertical curves located just beyond the exit nose should be designed with a minimum 80 kph stopping sight distance. Beyond this point, progressively lower design speeds may be used to accommodate loop ramps and other geometric features. Entrance Profiles - Entrance profiles should approximately parallel the freeway profile for at least 30 m prior to the inlet nose to provide intervisibility in merging situations. The vertical curve at the inlet nose should be consistent with approach alignment standards. Where large-truck volumes exceed 20 vehicles per hour on ascending entrance ramps with sustained upgrades exceeding 2%, a minimum 450 m long auxiliary lane should be provided to insure satisfactory separating conditions. Exit Ramp Transitions - Exit ramps in urban areas may require additional lanes at the cross road intersection to provide storage and increase capacity. If the length of a single lane ramp exceeds 300 m, an additional lane should be provided on the ramp to permit passing maneuvers. 508.01 RAMP TERMINAL DESIGN The ramp terminal is defined as the area where the ramp meets the cross road. Terminals - Ramp terminals should be treated as at-grade intersections. The terminal design shall be per Part 2, Section 400, At-Grade Intersections, based on near-minimum turning conditions.

Figure 500.16 Curved Entrance/Exit Locations From Caltrans, 1995, Highway Design Manual

Terminal Grades - Ascending off-ramps should join the cross roads on a reasonably flat grade to expedite truck starts from a stopped condition. Ramp terminals should connect where the grade

Part 2 500-16

ROADWAY DESIGN MANUAL – Roads and Bridges of the over crossing is 4% or less to avoid potential overturning of trucks.

movements are allowed within 125 m of the ramp intersection.

Terminal Locations - Factors which influence the location of ramp terminals include sight distance, construction costs, right of way costs, circuitry of travel for left-turn movements, crossroads gradient at ramp intersections, storage requirements for left-turn movements off the crossroads, and the proximity of other local road intersections.

Terminal Sight Distances Horizontal sight restrictions may be caused by bridge railings, bridge piers, or slopes. Sight distance is measured between the center of the outside lane approaching the ramp and the eye of the driver of the ramp vehicle assumed 3.0 m back from the edge of shoulder at the crossroads. Figure 500.17 illustrates ramp setback from an over crossing structure. This figure is based on sight distance being controlled by the bridge rail, but the same relationship exists for sight distance controlled by bridge piers or slopes.

Where a separate right turn lane is provided at ramp terminals the turn lane should not continue as a "free" right unless pedestrian volumes are low, the right turn lane continues as a separate full width lane for at least 60 m prior to merging, and access control is maintained for at least 60 m past the ramp intersection. Provision of the "free" right should also be precluded if left turn

Where ramp set back is unobtainable, sight distance shall be provided by flaring the end of the overcrossing structures or setting back the piers or end slopes of an undercrossing structure.

Figure 500.17 Ramp Setback From Caltrans, 1995, Highway Design Manual Part 2 500-17


SECTION 600 GEOTECHNICAL ENGINEERING

may be obtained through the Abu Dhabi Municipality Road Section as well as other Municipality and Government Agencies.

601

The geotechnical report is to contain the information shown in Table 600.01 as a minimum.

INTRODUCTION

The first part of this section is intended to give an overview of what is required in a geotechnical report used for roadway and structural design. It does not cover the specific methods of testing, sampling or analysis required. Standard SI practices and the “Municipality Roads Section Guidelines for Subsurface Investigations for Civil Engineering Purposes” current revision should be used for guidance in this area. The second part of this section outlines the pavement design procedure.

602

GENERAL

The Consultant shall obtain approval from the Road Section, Traffic Police and any other concerned Agencies prior to commencing a geotechnical investigation. Generally a geotechnical investigation is carried out in two phases. The initial phase consists of preliminary drilling and testing to gather enough project specific information to advance the roadway and structure design. The final stage, if required, is performed for design features requiring specific geotechnical recommendations.

603

GEOTECHNICAL REPORT

Once the preliminary horizontal and vertical alignment and structure locations have been defined, the engineer will prepare a preliminary a subsurface exploration and testing program. Providing information such as foundation types, safe slope angles and preliminary pavement thickness allows the initial design to be advanced and refined. The initial program also identifies the type, severity and extent of any geotechnical design problems. The geotechnical report should consist of results and recommendations from the initial drilling and testing program as well as any information from prior investigations. Prior investigations and data

Table 600.01

GEOTECHNICAL REPORT Table of Contents • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Introduction Location Map Proposed Construction Previous Information and/or Investigations Field Investigation And Laboratory Testing Include Boring Location Plan Site and Subsurface Conditions Climate Significant Geotechnical Features Regional Geology and Seismicity Analysis and Recommendations Retaining Wall Recommendations Excavation and Ground Compaction Factors Expected Settlements Groundwater Observations Allowable Foundation Loads Foundation Recommendations Borrow/Material Source Slope Stability Soil Corrosivity to Buried Structures Subgrade Support for Pavement Design Topsoil Plating Recommendations Treatment for Problem Soils Any Relevant Geotechnical Aspects Affecting Future Performance of the Works Appendices Boring Logs Summary of Test Results Other Pertinent Information

Pertinent information should be included in the appendices. In certain circumstances, such as a major bridge design or other major structure, an additional report may be required to define special geotechnical aspects of foundation design.

Part 2 600-1


The advantage of the phenomenological approach is that one does not need to spend resources on measurement of input variables. The advantage of the analytical approach, however, is that conditions outside the experience of the designer can be designed for by selecting the appropriate input variables.

STRUCTURAL PAVEMENT SECTION DESIGN

604.01 604.01.01

GENERAL Pavement Design Methods

Pavement design is a challenging process because the analytical framework for design is so complex. Complexity is introduced both by the number of materials involved and the number of variables required for design. The pavement section itself consists of a surfacing material and several supporting layers. The strengths and moduli of these layers vary through several orders of magnitude, and at least the lowest layer (native subgrade) is best described by non-linear constitutive models. These factors by themselves make development of equations which control even simple material behaviors such as deflection under load extremely non-trivial. The problem is exacerbated by the sheer number of variables which ought to be considered. The pavement is influenced by the soil upon which the pavement is supported, the number of vehicles expected to pass over the pavement, the weight of the vehicles which pass over, the spatial arrangement of the tires which support that weight, the tire pressure, the material properties of the pavement section materials, the temperature and temperature range, the moisture condition of the subgrade, the likelihood of freeze-and-thaw cycles, and probably several more. Many of these variables are extremely difficult to evaluate. The soil conditions under the pavement is evaluated at only a few points, and the weakest points are statistically likely to be missed. Traffic predictions are notoriously complicated and inaccurate. Furthermore, pavement failure is very difficult to define, as there are many possible failure modes. The analytical process underlying each failure mode is different. Generally speaking, there is a spectrum of design approaches which could be taken, ranging from polar extremes of purely analytical methods to purely phenomenological methods.

Actual pavement design methods fall somewhere between these two extremes. Field and laboratory investigation of pavement properties and performance over the last 20 to 30 years have led to semi-analytical methods based on observations. The many input variables are introduced either through equations developed by regression or equations developed from first principles. The TRIP pavement design method was based on the interim AASHTO method developed in the late 1970’s. The approach to pavement design has advanced considerably since that time. In order to take advantage of these advances several stateof-the art pavement design methods were evaluated against the TRIP method for use in the Municipality. The interim AASHTO method, upon which TRIP was based, was developed from the results of observations of roadway performance on test beds in the midwestern United States. This method was widely regarded as the best compromise between observation and analysis available in the late 1970's. However, because of its origins primarily in the Midwestern United States, the applicability of the method to other climates was questioned. Further, the characterization of the soil support was relatively unsophisticated, and there was no way to directly treat the desired level of confidence in the design. Economic analysis based on life-cycle was not explicitly incorporated. The method included no means for representing the statistical validity of the soil sampling or the traffic design. AASHTO continued researching the performance of pavements in the road test site to correct these problems after 1972. This research primarily consisted of more detailed monitoring of the test road beds, to allow better correlations to be drawn amongst more parameters than were included in the original method.

Part 2 600-2

ROADWAY DESIGN MANUAL – Roads and Bridges In 1986, a major modification was released which provided a significantly more sophisticated design and analysis tool. The improvements primarily were in the areas of failure definition, statistical treatment, and soil characterization. Performance and failure concerns were incorporated in the 1986 edition by virtue of then longer term monitoring of the pavement sections in the original test. Pavement condition was added through the Pavement Serviceability Index (PSI), a qualitative evaluation of ride condition using a Likert-type scale. Using this approach, it is possible to select the amount of condition change which constitutes failure. A model was developed which linked the change in the pavement condition over time to the usage and environment of the roadway. In addition to providing more performance-based design, this improvement also allowed life cycle cost analysis. The underlying concept of life-cycle analysis is to select a pavement solution for the transportation corridor, rather than for the pavement itself. Simply put, the idea is to consider pavement systems with a lower initial cost (perhaps due to thinner pavement) and a higher maintenance cost (including overlays) alongside methods with higher initial costs and lower maintenance costs. Because of the serviceability index concept, one can keep track of the changing pavement performance with time, and thereby determine the timing of major maintenance for economic analyses. Most modern pavement design methods utilize some form of life cycle analysis. Also new in the 1986 interim AASHTO method was treatment of statistical variability. The statistical variability of the input parameters and pavement performance are incorporated through two factors- reliability and standard deviation. The reliability factor accounts for chance variation in traffic prediction and performance by allowing the selection of a degree of confidence that the design will last the design period. The higher the desired degree of confidence in the design, the thicker the pavement. The standard deviation factor accounts for statistical variability in the input parameters, particularly the traffic predictions.

The last significant change was in the input parameter to use for describing the supporting soil strength. In the 1986 edition, the soil is characterized by the resilient modulus instead of the more nebulous soil support number used in the 1972 interim method. The resilient modulus is a measure of the soil behavior after thousands of load repetitions, and has come to be widely regarded as the most accurate characterization variable for pavement design. Climate is directly included in the resilient modulus determination through the boundary values used for the test. AASHTO released the final method in 1993. The most significant changes in the intervening years (1986-1993) concerned the design method for overlays and rehabilitation. A major evaluation of the performance of the design method and its underlying assumptions is currently underway in the United States, as part of the Strategic Highway Research Program (SHRP). This analysis includes detailed observation of nearly 800 test sections scattered across all parts of the United States, and an assessment of the ability of the AASHTO method to predict serviceability and performance. Preliminary results (SHRP, 1994) indicate that while traffic loadings are notoriously under-predicted (a non-conservative error), the results are to some extent offset by severe underprediction of field moduli in the laboratory resilient modulus test (a conservative error). The major change that is expected in the future will be direct analysis of each potential failure mode, rather than the serviceability approach currently in use, which lumps together many different failure modes. The AASHTO method has been modified by many individual state departments of transportation in the United States. The Arizona Department of Transportation method (ADOT, 1992) is optimized for the hot climate of the southwestern United States. The method is very similar to the AASHTO method, but deals more explicitly with the statistical variability of the underlying soils. The resilient modulus is the operative soil characterization variable, although due to difficulty in measurement of the resilient modulus ADOT uses a correlation with the Hveem Resistance Value (R-value).

Part 2 600-3

ROADWAY DESIGN MANUAL – Roads and Bridges Another method of potential interest is that used by the Ministry of Communications of the Kingdom of Saudi Arabia (MOC). This is a relatively simple method to apply, in which the soil is characterized by the CBR, and the traffic by a 16-kip equivalent single axle loading. Design charts are then entered to perform the actual design. roads are placed into two categories ("Expressways" and "Roads Other Than Expressways"), allowing some treatment of the desired level of reliability. Each of these methods incorporates all of the variables described in the beginning of this section, with the primary difference being the degree to which these variables are explicitly incorporated in the analytical portion of the analysis. In general, one can characterize the AASHTO method as closest to the analytical end of the spectrum, and the MOC method as closest to the phenomenological end of the spectrum. There are methods which are even more heavily weighted towards analysis, but these are most commonly used for research rather than practice. The methods described herein are considered representative of many methods in common use today, and are illustrative of the important factors in pavement design. 604.01.02

Comparison of Design Results

Calculations were performed using the newest AASHTO method, the ADOT method, and the MOC method and compared with the TRIP method. In order to simplify direct comparison of results, the comparison was based on Structural Numbers (SN) which result from each analysis, rather than on a comparison of the pavement sections themselves. This approach was used because the SN is the most useful design descriptor which results from the procedures, and because it is independent of the individual pavement layer components chosen by a given agency. High traffic, weak soil, or high degrees of conservatism will all yield higher SN values, and this number thereby allows direct comparison of the results of an analysis for similar input variables. For example, if two methods are used that generate vastly different SN values for the

same input variables, then one method can be said to yield a substantially more conservative design than the other. In the current case, we will compare the SN value for the original TRIP method with the newer design methods using a consistent set of material coefficients. A SN was developed for each roadway classification pavement section described in the DCIL TRIP report. The TRIP SN are compared to the SN resulting from each pavement design method used in this study in Table 600.02. Table 600.02 Comparison of Structural Numbers for Multiple Design Methods Design Method TRIP AASHTO ADOT MOC

Truck Freeway Main Sector Route Expressway Road Road 8.40 7.28 5.69 3.31 7.9-9.5 7.3-8.9 5.6-6.8 2.8-3.7 7.27 6.90 4.91 2.50 * * * 4.69

*Traffic values too far beyond the range of design charts to allow extrapolation. The AASHTO results show a range because of the correlation from CBR to resilient modulus required for the AASHTO method. A design CBR of 10 was used for the TRIP design. In order to correlate CBR to resilient modulus, AASHTO recommends the equation: Mr = 1500(CBR)

(Eqn. 1)

whereMr = Resilient Modulus (psi) CBR = California Bearing Ratio Equation 1 was used to develop the lower SN's shown in Table 600.02. However, there was considerable scatter in the correlation between the CBR and the resilient modulus, with the conversion factor ranging to as low a value as 750. In the absence of actual measured resilient moduli with which to evaluate the applicability of the AASHTO conversion, a conservative approach was adopted in which the design would be checked with a lower resilient modulus

Part 2 600-4

ROADWAY DESIGN MANUAL – Roads and Bridges corresponding to the lower end of the AASHTO correlation range: Mr = 750(CBR)

(Eqn. 2)

The highest SN shown in each classification for the AASHTO method results from a correlation to resilient modulus using Equation 2. This range should capture the range of results likely to result from actual resilient modulus testing. The ADOT method, which is also based on resilient modulus, was completed using the correlation recommended by AASHTO and presented here as Equation 1. The MOC method was only applicable for the lightest roadway classification, the Sector Road. In every other case, the design equivalent axle loading for the TRIP roadways was well beyond the inference space depicted on the MOC design thickness charts. This result comes about due to the degree of overloading common on TRIP roadways, rather than to an excessive number of vehicles. The MOC method is based on a 16-kip axle load, requiring a large destructive effect factor when considering that up to 27-kip loads were used in the TRIP report. As can be seen from Table 600.02, there is some variation in the results based on the method used. It is readily apparent that the TRIP thickness results are well within the range of modern pavement design methods. The TRIP results are well above the ADOT methods and firmly within the range of new AASHTO SN's. The method is non-conservative compared to the MOC method; however, this comparison is believed to result largely from the large truck overloads leading to huge traffic loadings compared to the 16-kip single axle loadings used for design in the MOC.

The 1993 AASHTO pavement design method has been used extensively in a variety of climates across the United States and many other parts of the world, and has been found to work effectively in a wide range of conditions. The pavement design method outlined below is based on the 1993 AASHTO method with modifications tailored to local conditions. The use of the AASHTO method will allow site specific treatment of individual roads within the Municipality of special importance or roads outside the Municipality on less familiar or less uniform soils. The following method should be used in conjunction with the 1993 AASHTO method for all Municipality pavement designs. 604.02

PAVEMENT DESIGN METHOD

Step 1: Develop Equivalent Single Axle Load, W18 Traffic is represented in the 1993 AASHTO method by the equivalent single axle load (ESAL), or the number of 18-kip equivalent single axle loads that will pass over the pavement during its initial service lifetime (typically 20 years). To calculate this value, three components are required: (1) the number of vehicles which will pass over the pavement during its lifetime, and (2) the breakdown of those vehicles by weight classification, and (3) a means of converting the number of vehicles in each class to an 18-kip equivalent single axle load. To estimate the total number of vehicles utilizing a pavement during its design life, existing and projected traffic volumes are needed. To determine the total number of vehicles, use a straight line interpolation between the existing traffic volumes and traffic volumes of the design year. For existing pavement studies, calculate the average rate between the existing traffic volume and the traffic volume of the design year. That average rate is then multiplied by the projected design life of the pavement. For new pavements the number of vehicles would be estimated using the design period.

The conclusion is that the major modifications to the AASHTO methods which have occurred since the original TRIP method was devised have not significantly altered the designs which would be recommended if the same input variables were used to start the design process today. The suitability of the input variables, both standard and road specific, is therefore the most appropriate question for the development of a new method. Of the methods examined, the 1993 AASHTO method is the most appropriate choice. Part 2 600-5

ROADWAY DESIGN MANUAL – Roads and Bridges The second component, the number of vehicles in certain weight classifications comes from detailed counts of vehicle types in the traffic mix at a variety of times and places within each roadway class. Finally, a means of converting the rough traffic numbers, broken down by vehicle class, to the 18kip equivalent single axle load is needed. The axle load equivalency factors used in the design method vary with the load on the axle, the type of vehicle, and the pavement thickness. See the AASHTO guidelines for a complete set of tables. It should be noted that these tables do not reflect the higher tire pressures that are often used in the Municipality. However, the tabulated values still form a good starting place for equivalency factors. For a simplified approach, the values in Table 600.03 form an acceptable interim approach: Table 600.03 Generic Equivalency Factors Vehicle Type Heavy Truck Medium Truck Light Truck Automobile

Equivalency Factor 6.5 1 .25 .0008

Step 2: Develop soil resilient modulus, MR The resilient modulus of the soil subgrade is required for design and must be measured or estimated. The AASHTO correlation below gives reasonable agreement between the California Bearing Ratio (CBR) and the soil resilient modulus. Unless site specific investigations determine different resilient modulus-CBR correlation factors, the AASHTO correlation should be used. Mr = 1500(CBR) where: Mr = Resilient Modulus (psi) CBR = California Bearing Ratio Step 3: Determine the overall standard deviation, So The overall standard deviation is a dimensionless parameter that accounts for random variation in the traffic projections and normal variation in the pavement parameters. Simply put, it provides a means of accounting for areas of weaker than average pavement receiving higher than expected traffic. A value of 0.45 for So is commonly used for flexible pavement materials. Step 4: Select the level of reliability, R

Using these values and counts or estimations of traffic loading within the classifications, the overall 18-kip equivalent single axle loading can be estimated. The advantages of the AASHTO equivalency factor approach outlined above are that (a) the method can be used with very little data about the traffic composition, or with very detailed traffic counts; (b) most other methods require very detailed information about tire pressures, wheel configurations, and load layouts, information which would be even harder to come by than the traffic counts, and (c) the equivalency factors can be easily and directly incorporated within the method. Ideally, detailed weight and composition data can be obtained to allow the development of system-specific equivalency factors, but the AASHTO factors can be used in the meantime.

The level of reliability describes the degree of certainty that the pavement will last as long as the design service period. Statistically, the thicker the pavement section the higher the likelihood that the pavement will last throughout its intended service life, other factors being equal. The level of reliability is represented in the AASHTO equation by the standard normal deviate, ZR, and in the design nomograph by R. Table 600.04 contains recommended values for the roadway classifications. The table contains very conservative values to reflect the need for high performing pavements in a high-growth, low maintenance management mode.

Part 2 600-6

ROADWAY DESIGN MANUAL – Roads and Bridges Step 6: Solve for the structural number, SN Table 600.04 Reliability Parameters Roadway Classification Truck Route Rural/Urban Expressway Main Road Sector Road

Level of Reliability, R R 99.9 99.9 99.9 99.0 95.0

Standard Normal Deviate, ZR -3.090 -3.090 -3.090 -2.327 -1.645

Step 5: Select design serviceability loss, ∆PSI

The preceding steps 1-5 were independent. However, a value must be obtained for each one in order to complete step 6, solving for the structural number. The structural number can be solved for using the equation below, using a trialand-error procedure. log10W18 = (ZR )(So) + 9.36log10(SN + 1) - 0.20 ∆PSI 4.2-1.5

log10 + 0.40 +

The pavement serviceability is a general measure of the pavements ability to service the traffic which must pass over it. Serviceability ranges from 0 (impassable) to 5 (ideal), and represents a quantification of subjective impressions about the roadway quality. Note that a low serviceability implies only that the road has become difficult to travel over, and provides no information about the failure mode (e.g. rutting, stripping, cracking) that has created the low serviceability. The design serviceability loss (∆PSI) is the allowable change from the initial serviceability (po) to the terminal serviceability at the end of the design period (pt). The design serviceability loss is obtained by simply subtracting the final value from the initial value, and so describes the amount of degradation of service which is acceptable during the design lifetime. Recommended values for the different roadway classifications are shown in Table 600.05.

Where: W18 MR SO ZR ∆PSI

Truck Route Freeway Expressway Main Road Sector Road

4.2 4.2 4.2 4.1 4.0

3.0 3.0 3.0 2.6 2.4

+ 2.32log10MR - 8.07

(SN+1)5.19

Equivalent Single Axle load, Step 1 Soil Resilient modulus, Step 2 Overall Standard Deviation , Step 3 Standard Normal Deviate, Step 4 Design Serviceability loss, Step 5

Or the solution may be obtained by using the nomograph in Figure 600.01 on page 600.10. Step 7: thickness

Determine

pavement

and

base

Once determined from step 6, the structural number is used to determine the thickness of each pavement material layer using the appropriate material coefficients from Table 600.06.

Table 600.05 Serviceability Parameters Roadway Initial Terminal Classification po pt

= = = = =

1094

Design Serviceability Loss, ∆PSI 1.2 1.2 1.2 1.5 1.6

Part 2 600-7

Table 600.06 Pavement Material Coefficients Pavement Coefficient Material (per cm) ai Asphaltic Concrete 0.17 Aggregate Base 0.05 Sand-Asphalt Base 0.08 Soil Subbase 0.04

ROADWAY DESIGN MANUAL – Roads and Bridges The structural number coefficients as follows:

is

related

to

the

Anticipated Construction Problems Consideration should also be given to the feasibility of the proposed design in regard to standard construction methods.

where: ai = material coefficient for each material in the pavement section (Table 600.06). ti = thickness of each material in the pavement section (cm). SN = Structural number desired for the pavement section (Step 6).

Costs - Comparative costs provided in the pavement design procedure should be given consideration in the selection of the pavement design. Consideration should also be given to maintenance cost.

SN = a1t1+a2t2+a3t3+...+antn

Various combinations of pavement materials of various thickness are possible to meet or exceed a given structural number. Once the structural requirements are met the combination and thickness of the individual pavement material sections is based on such factors as aggregate availability , aggregate size, cost of various pavement materials, minimum recommended thickness, restrictions on overall thickness, number of lifts required. These factors are discussed in more detail below. Material Availability - Conservation of natural resources should be given considered in the evaluation of the pavement design, and in areas where materials are scarce, availability should be given considerable weight. Continuity of Pavement Type - To maintain uniform driving conditions, consideration should be given to continuing the same type of exiting pavements, especially if a new project is relatively short. This is assuming that the existing pavements are satisfactory. Location and Local Conditions - Although there are many pavement designs that will meet the requirements of the design equation, there are situations when local conditions, such as underground utilities close to the surface, poor drainage, flooding, etc. where one design might function more efficiently than another. Past experience and judgement should be used in the final selection of the pavement design.

Minimum Structural Number - AASHTO design is based on traffic-induced fatigue failure. Establishing a minimum design takes into account such factors as ease of construction, maintenance, current practice or failure under the action of a few heavy design loads. Table 600.07 should be used as a guide for minimum pavement design. Table 600.07 Minimum Pavement Design Roadway Classification Truck Route Freeway Expressway Main Road Sector Road Low Volume

Minimum Structural Number 7.9 6.9 6.9 4.9 2.5 2.0

Minimum AC Thickness (cm) 30 28 28 21 11 6

Additionally on layered sections using aggregate base, a minimum thickness of 20 cm shall be used for the base material. Normally, the pavement section which satisfies the structural requirements and represents the least cost would be selected. However, as previously discussed, there may be times when the least cost design would not necessarily be the most appropriate design. The following page contains an example of a typical flexible pavement design.

Part 2 600-8


EXAMPLE FLEXIBLE PAVEMENT DESIGN Given the bold faced information, determine the pavement materials and thickness required for a truck route. Step 1 - Develop Equivalent Single Axle Load, W18 Vehicles Breakdown Table 600.03 per of Vehicles Vehicle Equivalency Factors Lifetime 338502756 5% Heavy Truck 6.5 5% Medium Truck 1 5% Light Truck 0.25 85% Automobile 0.0008 W18 =

W18 110013396 16925138 4231284 230182 131400000

Step 2 Develop soil resilient Modulus, Mr Mr = 1500CBR = 1500(10) = 15000 psi Step 3 Determine the overall standard deviation, So So = 0.45 Typical Step 4 Select the level of reliability, R Truck Route, Table 600.04 R = 99.9 ZR = -3.090 Step 5 Select design serviceability loss, PSI Table 600.05 po = 4.2 pt = 3.0 PSI = 1.2

Step 6 Solve for structural number, SN SN =8.0 Step 7 - Determine Material Thickness Table 600.06 Pavement Material Asphaltic Concrete Aggregate Base Sand-Asphalt Base Soil Subbase

Coefficient (per cm) 0.17 0.05 0.08 0.04

Trial SN Thickness Contribution (per cm) 30 5.1 22 1.1 0 0.0 45 1.8 Actual SN = 8.0

Note: Various material combinations can be compared economically to determine the optimum design. Make certain thickness meet Table 600.07.

Part 2 600-9

Figure 600.01


Part 2 600-10


SECTION 700 DRAINAGE 701

GENERAL

Drainage is an important element of roadway design. The objective of roadway drainage design is to provide the necessary facilities which allow the public the appropriate use of the roadway during times of significant runoff and which minimize the potential for adverse effects on adjacent property and existing drainage patterns. Toward this goal, roadway drainage design is to minimize off-project impacts while maintaining use of the roadway at an acceptable frequency of protection. There has been so much data and so many guidelines written on the hydrologic and hydraulic aspects in roadway design that it is impractical to contain all the references within this manual. A separate manual, “ROADWAY DESIGN MANUAL – Drainage,” has been prepared to provide guidance and direction on the design of the drainage components of roadway facilities. Strict use of that manual does not replace sound engineering judgment. The drainage design must be undertaken by experienced drainage engineers who are in responsible charge.

Part 2 700-1


SECTION 800 UTILITIES 801

GENERAL

Utilities are an important element of roadway design, especially in an urban environment. There are three categories of utility improvements: Utility Protection- Existing utilities within the project limits that have been determined to be geometrically compatible with the proposed improvements; and are in good condition with an acceptable remaining service life; may remain in place and must be protected from traffic loads and maintenance operations. The traffic loads consist of both construction loading and postconstruction vehicular loading. Utility Relocation- Existing utilities that are incompatible with the roadway geometrics will require relocation, which may extend beyond the limits of the proposed improvement depending on connection requirements. Relocated utilities will be replaced in-kind with the same size or capacity as the existing utility. The existing capacity may be undersized and require an increase in capacity or other utility expansions or improvements may be require. Such an up grade or development work must be requested by the responsible utility agency and approved by the Road Section before the design of the upgraded utility can be included in the roadway project. New Utilities- New service facilities that may be required to support growth within the typical 20year design life of the proposed roadway improvements; may replace redundant or outdated facilities or are major trunk lines routed through the project corridor that serve a broader purpose. Utility planning begins in the preliminary design phase and is a factor in the project scoping process that leads to identification of the final roadway geometrics. A thorough investigation of existing utility location and condition is undertaken as an early final design activity.

The Department’s objective is that Roadway and Bridge projects are developed to include all required construction of utility protection, relocation and installation by the Contractor. This provides for single source responsibility for the procurement of materials, and the scheduling of the proposed improvements; while minimizing disruption of services to the public. This concept reduces Contractor delay claims and the time required for advance utility works. The actual timing and responsibility for construction of individual services will be determined on a project by project basis. Although contained in a single set of construction documents, there are normally several Consultants involved in the preparation of individual utility plans, specifications and BOQ. Several Municipality Departments use designated Consultants for the planning and design of their respective services, as further described in Section 804.01. The Roadway/Bridge Consultant is responsible for overall coordination and packaging of the documents into a complete and comprehensive set of tender documents. The parallel development of plans and specifications by multiple Consultants must be continuously monitored to avoid conflict and contradiction.

802

UTILITY PLANNING

The Utilities Section of the Town Planning Department is responsible for master planning and coordination of utility services. Service corridors will be reserved within each project for utilities in accordance with the planning data obtained from the Utilities Section. The corridors are established based on the approved design concept and reflect the anticipated growth and overall needs of the individual utility agencies. The agencies or Municipality department responsible for the individual services are as follows: • • •

Part 2 800-1

Water - Water and Electricity Department (WED) Telephone and Telecommunications ETISILAT Drainage - Abu Dhabi Municipality Sanitary Drainage Network Division

ROADWAY DESIGN MANUAL – Roads and Bridges • • • •

Electricity - Water and Electricity Department (WED) Irrigation - Abu Dhabi Municipality Agriculture Section Sewer - Abu Dhabi Municipality Sewerage Projects Committee. Gas Line - Abu Dhabi National Oil Company.

The Utilities Section will provide details on the agency or department responsible for special services such as oil and gas pipelines, 132 KV and national defense systems. Information on existing utilities shall be obtained from the Town Planning Utilities Section, the individual Service (Utility) Departments and/or the designated Consultant at the beginning of design work. This data will include: • • • •

Current Service Reservation Locations Distribution of Services As-built Drawings Proposed Facility Plans

This information shall be compiled and analyzed to ascertain the status of each individual utility. Utility data should be supplemented by field investigation of the existing facilities including surveys to record structure locations and pipe invert elevations. Manual(by hand) excavation to locate services that are critical to the design should be performed as necessary. The Consultant will arrange coordination meetings with the Service Departments to identify utilities to be protected, relocated to the service reservations and new service requirements. The service authority may also have plans or projects for utility improvements in progress within the project limits. Once the scope of the utility works has been defined, the Consultant will prepare separate cost estimates of the utility works that are required due to conflict with proposed works and new facilities that are proposed for inclusion in the project by the utility agencies. It is important to make a clear distinction between required works and facility upgrades, since this information will be used to determine the extent of the utility works to be included in the project and cost sharing responsibilities. The Department will

review and give final approval of the project utility scope of works. The utility planning process is depicted on Figure 800.01.

803

SERVICE RESERVATIONS

The Department’s objective is to locate all utility services in designated utility corridors or Service Reservations. This policy applies to all projects including new construction and roadway widening. Service reserves are located for ease of construction and maintenance and to minimize disruption or damage to permanent works caused by future utility installations or maintenance operations. The reserves are generally located outside the roadway pavement in parking or pedestrian areas that are surfaced with removable materials including interlocking tiles and precast tile blocks, and asphalt pavements of reduced thickness. Roadway crossings are perpendicular to the centerline and primarily concentrated at intersection locations. The design standards require construction of ducts for all existing, proposed and future services that cross roadway pavement. The utility corridors are defined in close coordination with the project geometrics and the Town Planning Department. The reserves are established within geometric criteria that is suited to the installation of pipelines and conduits. Alignments are as straight as possible and angle points limited in severity with the degree of deflection ideally corresponding to pipeline fittings (22-1/2, 45 degrees). The Standard Drawings show several different distributions of standard service reservations. Special reserves for any utilities other than those shown on the standard drawings (CCTV, 132 KV, gas, oil.) shall be provided in each project with specific approval from the Town Planning Department. Project design drawings should show a section view of these special service reserves similar to that shown on standard drawings. Deviations from the standard distribution may be warranted to: • • •

Part 2 800-2

Accommodate existing utilities that would not otherwise require relocation. Suit the project geometrics. Allow for constructability and/or maintenance of service facilities with excessive width, diameter or depth.

ROADWAY DESIGN MANUAL – Roads and Bridges The final Service Reservation distribution and geometry requires the approval of the Town Planning Department.

804

UTILITY DESIGN

804.01 GENERAL Utility design requirements will be defined on final determination of the scope of utility works by the Department. The final design of each utility will proceed based on the existing utility information and proposed facility requirements. Refer to the Utilities Procedures Flow Chart, Figure 800.01. In general, rapid development, incomplete as-built information and the harsh soil conditions make it difficult to determine the exact requirements for each service line, especially minor branches and connections, without the benefit of an extensive manual excavation program to locate the utilities. As a result, this effort should be accomplished during the construction phase to enable preparation of detailed shop drawings that will fully define the requirements for each utility. The procedure and specifications for this work are oulined in the Standard Specifications. The tender documents are prepared based on the best available information and may be limited to the major components of a particular service. This procedure varies with the different utilities and generally can be described under three categories: Separate Plans and Specifications Prepared by Agency Designated Consultant- WED(Water) and Sanitary Drainage Network Section use a designated Consultant for the design of facilities. Final design plans, specifications and BOQ are prepared as separate documents and included in the project tender document package. The drawings will indicate the existing facilities anticipated to be protected, relocated or abandoned as well as new pipeline requirements. Based on the results of the manual excavation, the Contractor will prepare detailed shop drawings that include refinements and adjustments to the tender drawings to reflect the conditions encountered in the field. The shop drawings require the approval of the designated Consultant and the WED.

Separate Plans and Specifications Prepared by Utility AuthorityWED(Electric) and ETISILAT normally prepare design plans and specifications for their facilities in-house. WED develops schematic drawings and estimated quantities for relocation, protection, salvage and supply of new cables for inclusion in the tender documents. The drawings and Bill of Quantities are modified as necessary by the authority based on the results of the manual excavation and issued to Construction. The Contractor will then prepare fully detailed shop drawings for final approval by the WED. ETISILAT normally prepares detailed plans and specifications for the work based on their record drawings of the existing telephone system and the need for relocation or protection of plant impacted by the improvement project. These drawings are normally included with the tender documents. Any necessary adjustments based on manual excavation will be done through the shop drawing process in construction. Consultant Prepared Plans and SpecificationsThe prime Consultant for the improvement project is required to prepare final design plans and specifications for Surface Drainage, Lighting, Traffic Control and Drainage/Irrigation. The designs are prepared in consultation with the agency or department and the drawings are normally prepared as separate documents and included with the project tender document package. Any necessary adjustments based on manual excavation will be done through the shop drawing process in construction. 804.02

UTILITY PROTECTION

All utilities under the roadway must be protected. This protection will continue under all pavements and extend beyond the back of curb, edge of shoulder or at the duct end wall constructed at the end of the duct by 0.50 meters. The Standard Drawings and General Specifications outline the type of protection to be used for the various utilities consisting of three types: • • •

Part 2 800-3

Concrete Slab (Precast or Cast-in-Situ) Concrete Encasement Split Sleeve Concrete Encased

ROADWAY DESIGN MANUAL – Roads and Bridges These methods are designed to protect the utility from induced traffic loading including construction equipment loads. The Consultant should check that the depth of existing utilities is sufficiently below the subgrade level to accommodate the protection device. 804.03

UTILITY RELOCATION

Utility relocation will generally be determined by the individual utility agency and is subject to approval by the Municipality. Each agency will supply their relocation design drawings for inclusion in the Project documents. These drawings will then be reviewed by the Municipality to obtain their approval prior to inclusion in the Tender Documents. No utilities other than lighting, underground cables, and irrigation pipes shall be installed along the central median parallel to the roadway. These lighting cables and irrigation lines in the median shall be as close as possible to the curb to avoid disturbance to the greenery. Quantities, except for relocation work designed by a designated utility consultant, shall be calculated by the primary Consultant. WED(E) and ETISILAT will supply respective relocation quantities. Supply of all the materials required for the relocation works for electrical shall be included in each contract. Removed and salvaged LV, 11 KV and 33 KV cables excluding joints from site can be reused for the relocation works if approved by the WED. Quantities for the supply and salvage items shall be as estimated by the WED for each project. All 132 KV cables required for the relocation work shall be new and shall be supplied under each contract. 804.04 CONTINGENCY DUCTS Contingency ducts are required at roadway crossings for future services to be located in service reserves and at other specific locations established by the utility authority. Ducts are installed where pavements with asphalt or nonremovable pavers cross over the service reserve.

conduits may be placed in split ducts and concrete encased. Duct bank ends are terminated outside the permanent pavement in a reinforced concrete end wall structure that allows access to the duct ends without damaging the integrity of the structural pavement section. These are required at all multiple duct service reserve crossings. The end wall design and details are included in the Standard Drawings. All duct crossing locations are to be marked in the field with permanent markers as shown in the Standard Drawings. These markers are placed at the end of the duct or set in the top of the duct end wall concrete. 804.05 UTILITY LOCATIONS With the exception of lighting cable and irrigation distribution lines, there shall be no construction of utility lines such as power distribution lines, water lines, sewer lines, storm waterlines or any other lines in the central median of primary roads. Utilities of all kinds shall not be constructed under main roadway asphalt pavement. Utility lines can be installed in service reserves under sector roads or parking areas where asphalt pavement is reduced in thickness. 804.06 NON-DISRUPTIVE ROAD CROSSINGS Utility crossings of completed permanent works, especially Main Roads, Expressways and Freeways are to be avoided. Contingency ducts or alternate routes should be used to accommodate the service requirements whenever possible. When the crossing of primary roadways is unavoidable, Department policy requires the design to specify non-disruptive methods(pipe jacking) or tunneling to cross the facility. This should be a performance based specification to offer the Contractor flexibility in selecting the equipment and methods.

These ducts may be designed to accommodate existing or proposed service facilities with spare or reserve capacity for future (contingency) installations. Existing facilities such as cables or Part 2 800-4


Existing Utility Data Town Planning Utilities Section P L A N N I N G

Utility Agency As-Built Drawings Design Concept

Determine Conflicts

Geometric Adjustment

New Utility Requirements

Define Utility Scope of Work Utility Agency Approval

Service Reserve Dwgs. Prepare Cost Estimates Town Planning Approval Department Approval

D E S I G N

Utility Design

Agency Design

Consultant Design Coordination Tender Documents

Designated Consultant

Notice of Intent C O N S T R U C T I O N

Manual Excavation As-Built Drawings

Tender Drawings Existing Utility Shop Drawings Agency Review

Consultant Review Revised Design Drawings - RFC

Designated Consultant

Service Reservations Utility Works Shop Drawings Agency Approval

Town Planning Approval Resident Engineer Approval

Designated Consultant Construction Record Drawings

Figure 800.01 Utility Procedures Flow Chart

Part 2 800-5

ROADWAY DESIGN MANUAL – Roads and Bridges 3. 4.

SECTION 900 TRAFFIC ENGINEERING 901

5.

TRAFFIC OPERATIONAL ANALYSIS

901.01 GENERAL Part 1, Section 200, Design Concept Development, of this manual discusses traffic counts and traffic projection methods suitable for the design concept phase of a project. Part 2, Section 200, Geometric Design Standards, outlines the data required to develop a preliminary parking demand analysis for inclusion in the Design Concept Report. Final design may require refinement of concept data before a final traffic report can be completed. Specific model updating may be necessary to incorporate roadway network changes and revised roadway classifications. Model output shall be calibrated to reflect current traffic trends by comparing the present actual traffic volume to a current model run and applying corrective adjustments to depict the actual conditions. Model output shall be refined, particularly ramp volume and intersection turning volumes, to balance the daily traffic volumes from network link to network link. Directional design hourly volumes shall be derived in a manner similar to the daily volume adjustments. Sub-modeling computer programs should be used to determine the roadway volumes associated with the proposed frontage roads and other roadway characteristics not incorporated in the original model. 901.02 OPERATIONAL ANALYSIS The final traffic report should include an operational analyses utilizing the balanced traffic volumes determined from the traffic forecasts. The analysis will follow procedures and methods of the Highway Capacity Manual, By the Transportation Research Board and will include: 1. 2.

Ramp intersection capacity analysis. Ramp merge/diverge analysis.

Freeway weaving analysis. Basic segments capacity and operational analysis. Intersection capacity and operational analysis.

Signal warrant analysis shall be performed to determine the need for signals at an intersection. The Manual on Uniform Traffic Control Devices (MUTCD) signal warrants shall be used for this purpose. All necessary traffic engineering studies required for signal warrants shall be conducted. Where necessary, intersection simulation analysis shall be performed using a microscopic simulation program that models individual vehicle flow. Optimal phasing/timing and coordination parameters shall be used in the above mentioned operational and capacity analyses. For interchanges, conceptual designs will be assessed and recommendations provided for modification. Interchange operational analyses shall be performed to assess alternative concepts once the general plans of the alternatives have been developed. Lane configurations and the required turn-lane storage shall be designated at all intersections, furthermore, lane requirements of the freeway, mainline, ramps, cross-streets and frontage roads. The designations shall be a direct result of the analyses performed and shall be incorporated into roadway and bridge design drawings.

902

SIGNALIZATION

902.01 TRAFFIC SIGNAL DESIGN Traffic signal phase and phase interval sequence diagrams shall be provided for intersections and interchange ramp terminals. The signal system design shall include the following: • • • • • •

Part 2 900-1

Signal pole locations Mast arm orientation and lengths Signal head locations on mast arms and poles Signal face types Conduits (ducts) location, including spares Local Signal Controller and Changeover Switch foundations locations

ROADWAY DESIGN MANUAL – Roads and Bridges • • • • • • • • •

Red Violation Camera Loops and foundations locations Closed Circuit Television (CCTV) Poles and CCTV Controller foundations locations Pedestrian signals locations and placement Free Right Turn signal foundation locations Pullboxes types and locations Cabling requirements and terminations Grades for system conduits (ducts) and location of system detectors Local intersection inductive detector loops requirement, design and locations Master Controller foundation requirement and location

Phasing information should be used as a guide in determining which phases and interval sequences shall be provided at a specific location. New signals should be synchronized with the existing Arterial Progression System and/or the Central Computer Control System at the Traffic Computer Center. All traffic signals and associated equipment shall be in accordance with the Standard Specifications. Any variance relating to equipment type or performance shall be approved in writing by the Abu Dhabi Municipality. 902.02 SIGNALS, POLES, AND CONTROLLERS Only mast arm signal poles as per the standard drawings shall be utilized. Combination mast arm signal and lighting poles or poles with multiple mast arms will not be used. All signal lenses shall be 30 cm including arrow lenses. All signal heads shall be pole or mast-arm mounted. Span-wire mounted signals will not be used. Pedestrian signals will normally be installed in pedestrian pylons. Where appropriate, pedestrian signals shall be installed on the traffic signal pole, on a street light pole, or on a separate 3.2 m pole. Pedestrian signals will have two signal sections with 30 cm lenses. The graphic symbols for ‘WALK’ and ‘DON’T WALK’ shall be used. When illuminated, the DON’T WALK indication (hand palm) shall be red, and the WALK indication (man walking) shall be green.

A signal head shall be comprised of one signal face only. Typical signal locations shall be as follows: 1. A minimum of one signal face shall be provided for each separate vehicular movement and a minimum of two signal faces shall be provided for each through or major movement. 2. Vehicular signals shall be placed in such a way so as to provide clear visibility to approaching traffic. They shall be located no less than 12 m or no greater than 35 m beyond the stopline. Supplemental signal heads shall be used only when warranted, and after a detailed study of the location is conducted. There shall be one eight-phase, dual ring, single entry, fully actuated microprocessor based controller per intersection interconnected with existing systems as required. The controller shall be equivalent to a menu-driven NEMA type controller with LCD display capable of operating in a closed loop coordination system. Signal control details including signal plans and all traffic signal parameters for signal controller operation at an intersection/interchange shall be provided. A note shall be included on the plans and specifications stating that the control cabinet is to be wired with the same phase number designations as shown on the plans. Traffic signal systems shall include inductive loop detectors with adequate size, shape and number of turns to provide proper actuation. Loop detectors in bridge decks will normally utilize preformed loop detector material. Saw cutting of detector loops in newly poured bridge decks will not be permitted. Detector loops so located shall be cast integral with the bridge deck. Separate loop wires for each loop shall be provided. There shall be a splice to connect the loop wires to the lead-in cable in the curbside pullbox. This lead-in cable shall be terminated at the detector amplifier in the local intersection controller. There shall be no splices in the lead-in cable.

Part 2 900-2

ROADWAY DESIGN MANUAL – Roads and Bridges Where feasible, power feeds for traffic signals should come from two separate substations and be controlled by a changeover switch. This will enable signals to remain functional in the event one of the substations loses power. Separate feed plans should be developed in cooperation with the WED.

If the width of the roadway median at the intersection is more than 5, but less than 10 meters, an additional pylon is placed at the midpoint of the median with two pedestrian signals back to back. If the median width is more than 10 meters, one pylon is placed at each edge of the median, each with one pedestrian signal.

The signalization design for each intersection shall include as a minimum:

Each pedestrian signal is comprised of two signal units with WALK and DON'T WALK indications. The DON'T WALK unit, mounted on top of the WALK unit, has a polycarbonate lens with black background and an illuminated red “human hand” symbol placed vertically. The WALK unit, mounted below the DON'T WALK unit, has a polycarbonate lens with black background and an illuminated green “walking man” symbol.

1. Plan symbols as shown on the standard drawings. 2. A drawing of the overall layout depicting signal pole, detector, signal head and conduit placements. All vehicular and pedestrian signal indications shall be labeled by movement (signal group) number. 3. A drawing including the pole schedule, detector schedule, clearance times matrix, phase movements, and if necessary, notes specifically corresponding to the design and installation. 4. A drawing showing the conductor schedule. 5. Additional drawings as necessary for installation and materials details. 902.03 DUCTS AND PULLBOXES All ducts shall be encased in concrete. Based on the requirement, either 8-way, 4-way, 2-way or 1way 10 cm diameter ducts shall be utilized. Raceways shall be 2-way 5 cm diameter except for the traffic signal pole foundations raceways which shall be 3-way 5 cm diameter raceways. Standard pullboxes types (Type I, II and IV) shall be used as appropriate. 902.04 PYLONS Pylons are used to house the pedestrian signals. Their appearance and materials are meant to add color to the streetscape. They are comprised of an aluminum tube column base and an aluminum crown. External color is dark bronze. Pylons with Type B crown are used at all signalized intersections where pedestrian signals are required unless pedestrian signals can be mounted on nearby light poles. Pylons with Type B crown are placed within green areas at both ends and at the outer edge of pedestrian crossings.

903

TRAFFIC SURVEILLANCE

Communication system facilities shall be installed on main roads, expressways and freeways. The system will communicate traffic conditions to a central computer, which will then communicate back with the ramp signals, changeable message signs and TV cameras. Interconnections between signalized intersections surveillance facilities and the central computer will be through concrete encased, 4-way or 8-way 10 cm PVC ducts. CCTV cameras are to be located at intervals of approximately one mile. Typical camera locations will be at interchanges and at midpoint locations between interchanges. To provide for future implementation, 2 stub-outs of 10 cm diameter schedule 40 PVC conduit, 1 m long, will be extended from a pull box nearest the midpoint between interchanges. All conduit shall be securely capped and locations precisely recorded on “as-built” plans. The locations, numbers of ducts and foundations will be determined from the CCTV Master Plan drawings.

904

SIGNING

General - Discussion in this section is complimentary to the MUTCD and shall be used in conjunction with that document. However, policies presented in the MUTCD reflect general practices which may not always be applicable to Abu Dhabi. Where there are conflicts between

Part 2 900-3

ROADWAY DESIGN MANUAL – Roads and Bridges this section, the Standard Drawings and the MUTCD, the guidelines in this section and the Standard Drawings should be followed, consistent with sound engineering practices and judgement.

1.

Designating the lane use at forks of major inter-city expressway routes.

2.

Where roadway and ramp configurations may be misleading without lane designations, such as: locations where the through expressway lanes end beyond the interchange in a terminal, or locations where two or more ramps depart from the through lanes and require lane use demarcation for clarity.

3.

Where lateral space is unavailable for a ground mounted sign.

Traffic signs are installed to regulate, warn, and guide road users. Installation, reflectivity, legend size, legend color, placement, and support type should all be considered to provide a consistent, safe and informative signing plan. 904.01 SIGN STRUCTURE INSTALLATIONS 904.01.01

Ground Mounted

Ground mounted signs are unobtrusive and can provide drivers with the essential information in most instances. They are appropriate for marking all intersections and most interchanges. Typical guide sign treatments at expressway interchanges with main roads are diagrammed in Figure 900.01 and Figure 900.02. Sign post lengths are to be calculated based upon the Standard Drawings and the roadway cross section at the sign locations. Foundations for stubs shall be flush with the ground and stub protrusions of the concrete foundation shall also conform to the Standard Drawings. Signs installed in the median are to be designed for the ultimate roadway section. 904.01.02

Overhead Mounted

Overhead signs may detract from the aesthetic appearance of the roadway and architectural treatment of bridge structures. They also limit the clearances for large trucks and their loads. As a rule, overhead signs should be used sparingly at locations where ground mounted signs cannot provide the essential directions to the motorist. Overhead guide signs are principally applicable for marking free flow traffic movements at interchanges between rural expressways where lane orientation is necessary for directing the motorist, or at locations where lateral space for ground mounted signs is not available. Overhead guide sign use should be limited to:

At interchanges between rural expressways, it is desirable to sign the through expressway lanes in addition to the ramp lanes. This can be accomplished with a ground mounted guide sign in the median, if the median is wide enough. If the median width is inadequate, the through lanes guide sign may be cantilevered overhead in the median. The ramp sign may also be cantilevermounted for uniform appearance. Similarly, space for other ground mounted guide signs may be restricted, thereby indicating the use of an overhead cantilever mounting. Typical overhead guide sign treatments at major rural expressway junctions are portrayed in Figure 900.02. Tubular Structure - Advanced guide and exit direction signing on the mainline shall use tubular cantilever and tubular sign bridge structures. The Standard Drawings have tubular sign structures which have been developed to accommodate sign panels up to 4 m in height including the exit panel. Therefore, all efforts should be made to limit sign panel heights to 4 meters. This may require some minor reductions in legend size or spacing. The use of sign panels in excess of 4 m in height will require a complete sign structure design. Tubular sign structure standards shall be incorporated in the final plan submittal. Interchange sequential signs shall be located in the center of the median back to back on a single structure approximately halfway between

Part 2 900-4

ROADWAY DESIGN MANUAL – Roads and Bridges interchanges. Existing structures shall be utilized for sign mounting wherever possible. Bridge Mounted - Sign mounting brackets, for bridge mounted signs, are to be designed based upon the criteria set forth in this manual for sizing sign panels. Cast-in-place anchor bolts shall be provided with the bridge structure, together with all the necessary hardware for sign lighting.

Route markers shall be placed as separate signs and in conjunction with guide signs as shown in Figures 900.01 and 900.02. The background used for route markers shall be the falcon symbol shown below. The sign panel shall have a yellow legend and border on a blue background. Guide post types and lengths shall be as per Figure 900.04 and the Standard Drawings.

904.02 SIGN SHEETING Sign panel materials, reflectivity and color shall be per the Standard Drawings and the Standard Specifications. Any changes to the standards shall be approved in writing. 904.03 SIGN TYPES 904.03.01

Regulatory And Warning Signs

Regulatory and warning signs inform drivers of traffic regulations and warn of potentially hazardous conditions. Messages are portrayed using standard international symbols. These signs are generally less than one square meter in area. Post types and lengths shall be as per Figure 900.03 and the Standard Drawings. Locations shall be per the Standard Drawings and the MUTCD. 904.03.02

Guide Signs

Guide signs direct drivers to their destinations by informing them of intersecting streets or prominent places along the route. Messages shall be shown in both Arabic and English and vary in length and height. Space for these messages require large sign faces as well as structural supports. The guide signs may be ground mounted on the side of the roadway or mounted overhead above the roadway or shoulder. Guide signs shall be placed and designed per the Standard Drawings, the Standard Specifications and the MUTCD.

904.04 FINAL SIGNING PLAN REQUIREMENTS The final signing drawings should include information and details not covered by the Standard Plans or Specifications such as: • Site specific sign details • Sign Layout Sheets with sign dimensions, character dimensions, sign message, support type and reflective sheeting requirements. • Plan sheets showing sign placement. Signing sheets may be combined with striping sheets as long as the plans are legible. Scale shall be such that all signs and markings are clearly depicted.

Part 2 900-5


Figure 900.01 Guide Sign Treatment Interchanges With Main Roads Part 2 900-6


Figure 900.02 Guide Sign Treatment Major Junctions Between Rural Expressways

Part 2 900-7


Figure 900.03 Sign Installation And Post Selection Part 2 900-8


AISC DESIGNATIONS DIMENSIONS IN CENTIMETERS TWO POSTS

POST TYPE A = W6x15 POST TYPE B = W10x22 POST TYPE C = W14x26 SIGN DEPTH (cm) 91,107 122,137 122,137

SIGN WIDTH (cm) Up to 600 Up to 500 501 to 600

POST TYPE

153,168 153,168 183,198

Up to 400 401 to 600 Up to 350

A B A

183,198 213,229 213,229

351 to 600 Up to 250 251 to 600

B A B

244,259 244,259 244,259

Up to 200 201 to 500 501 to 600

A B C

274,290 274,290 274,290

Up to 200 201 to 400 401 to 600

A B C

305,320 305,320 335,351

Up to 350 351 to 600 Up to 350

B C B

335,351 366,381 366,381

351 to 600 Up to 300 301 to 600

C B C

Note: For signs wider than 600 cm, use 3 posts.

Figure 900.04 Sign Post Types Part 2 900-9

A A B

ROADWAY DESIGN MANUAL – Roads and Bridges 904.05 ARABIC LETTERING FOR GUIDE SIGNS 904.05.01

General

Guide signs shall be designed in Arabic and English, with the Arabic message above the English translation. To size the signs, the actual width of the Arabic and English messages must be determined. 904.05.02

The Arabic Alphabet

The first letter in the Arabic alphabet is “aleph” which is a simple downstroke. For the purposes of the Standard Script, aleph is used to proportion the height of the letters. In developing the Standard Script, it has been determined that an aleph height of 30 cm generally corresponds to signing on freeways, while an aleph height of 24 cm corresponds to signing on arterial roads. Figure 900.05 provides spacing criteria for Guide Sign design. Figures 900.06 through 900.17 are template guides for Arabic letters and numerals. When designing guide signs for all Abu Dhabi roadway projects, signs to be read from freeways and expressways will have 30 cm (aleph height) Arabic lettering and 27 cm English lettering. Signs to be read from ramps and main roads will have 24 cm (aleph height) Arabic lettering and 20 cm English lettering. 904.05.03

Use of the Standard Arabic Script

The shape of each letter and number in the Standard Script is shown on a five-millimeter grid in Figures 900.06 through 900.17. To get the actual width of a word on the guide sign, find the width of each letter shape in the Standard Script. Then multiply that width by the proportion of the aleph height in the final guide sign to the aleph height shown in the Script. Finally, add the width of each letter shape, taking into account the spacing rules for unconnected letters to obtain the total message width.

quite a distance below this baseline; therefore, the vertical spacing on the sign face should be checked and adjusted, if necessary. The width of the message “Corniche Road” is calculated in Example 900-01 on the following page. The page numbers refer to the fourteen pages in the Standard Arabic Script for Highway Signs, Section 904.07. Aleph height was assumed to be 24 cm, slightly larger than the English 20 cm lettering. Calculations proceed right to left. Looking at the last letter in the first word, the shape extends 43 mm below the baseline. Using the proportion of 4.8, at least 20.64 cm will be required between the Arabic and English message to avoid conflict. 904.06 GUIDE SIGN DIMENSIONS 904.06.01

Single Message Guide Signs (Example 900-02)

After computing the preliminary sign width (message width, arrow width, and offsets) it shall be rounded to the nearest 5 cm to get the final sign width. Changes to the adjustable base dimensions most likely will have to be made to achieve this. Sign faces shall be detailed as per the theoretical height dimensions for a particular sign. Small variations in the spacing between the legend and the border can be used to increase or decrease the overall sign height to an even 50mm increment. However, any reduction shall be limited to 90% of the original spacing. Changes made to achieve the recommended height and width shall be spread as evenly as possible over the appropriate adjustable dimensions. If the preliminary sign height or width is a halfway between two recommended sign heights or widths, always round to the higher size. Center the smaller lettering with the center of the wider lettering.

Arabic lettering is aligned on a baseline, just as in English. The location of the baseline for each letter is indicated by an arrow (V) adjacent to that letter in the Standard Script. Some letters extend Part 2 900-10


Proportion:

24 cm = 4.8 5 cm

First letter: Second letter: Space: Third letter: Space: Fourth letter: Space between words: First letter: Space: Second letter: Third letter: Fourth letter: Space: Fifth letter: Space: sixth letter: Seventh letter: Eighth letter:

page 6; connected on left: Page 3; connected on right from Table A, 1-1/2 squares: page 5; unconnected: from Table A, overlap by 1-1/2 squares: page 9; end of word: 6 squares: page 3; unconnected: from Table A, 1-1/2 squares: page 11; connected on left: page 10; connected both sides: page 12; connected on right: from Table A, no space: page 5, unconnected: from Table A, overlap by 2 squares: page 11, connected on left: page 12, connected both sides: page 6, end of word:

55 mm x 4.8 10 mm x 4.8 7.5 mm x 4.8 30 mm x 4.8 7.5 mm x 4.8 53 mm x 4.8 30mm x 4.8 8 mm x 4.8 7.5 mm x 4.8 22 mm x 4.8 50mm x 4.8 45mm x 4.8 30mm x 4.8 -10 mm x 4.8 22 mm x 4.8 27 mm x 4.8 80 mm x 4.8

= = = = = = = = = = = = = = = = = =

26.40 cm 4.80 cm 3.60 cm 14.40 cm -3.60 cm 25.44 cm 14.40 cm 3.84 cm 3.60 cm 10.56 cm 24.00 cm 21.60 cm 0.00 cm 14.40 cm -4.80 cm 10.56 cm 12.96 cm 38.40 cm

Total Length of Message

=

220.56 cm

Example 900-01 Sample Calculation Of Arabic Message Width Part 2 900-11


•

Multiple Message Guide Signs (Example 900-03)

For multiple message guide signs, the rules and base dimensions for a single message guide shall apply, with a few additions and exceptions. Guide sign width shall be determined by the widest message (message width, arrow width and offsets), measured as if it was a single message guide sign. To achieve a recommended height, changes in he adjustable dimensions should be spread as evenly as possible throughout all messages. The multiple sign should be shown with a similar dimensional breakdown as the single message sign (Example 900-02).

•

•

Separate guide arrows for each message (multiple messages): •

•

The following paragraphs provide guides for use with messages containing arrows. Separate guide arrows for each message: •

•

•

The smaller message shall not be centered with the larger message, but placed with the same offsets from the guide arrow side of the sign as if they were a single message sign. A single white stripe of 3 cm or 5 cm shall be placed between all messages that use separate guide arrows. English and Arabic lettering shall be offset from this line as from the border stripes in a single message guide sign. It is preferable to place the guide arrows on opposite sides of the guide sign.

These multiple messages shall be centered with the center of the largest message. The dimension between two messages shall be the same as between the Arabic lettering and the upper border stripe on a single message guide sign. The guide arrow shall be vertically centered. It will also be horizontally offset from the largest message as in a single message sign.

•

The smaller messages shall not be centered with largest message, but placed with the same offsets from the guide arrow side of the sign as if they were a single message sign. A single white stripe of 3 or 5 cm shall be placed between all messages that use separate guide arrows. English and Arabic lettering shall be offset from this line as from the border stripes in a single message guide sign. It is preferable to place the guide arrows on opposite sides of the guide sign.

Same guide arrow for multiple messages: • •

•

Separate guide arrows for each message:

Part 2 900-12

These multiple messages shall be centered with the center of the largest message. The dimension between two messages shall be the same as between the Arabic lettering and the upper border stripe on a single message guide sign. The guide arrow shall be vertically centered. It will also be horizontally offset from the largest message as in a single message sign.


Dimensions For Guide Signs Aleph Height

24 cm

30 cm

3 20 20

5 27 27

A B* C D E F* G* H* J K

(See Note A) 24 24 35 30

(See Note B) (See Note B) (See Note C) (See Note D)

30 30 40 40

(A) 10 cm + largest distance an Arabic letter in the message goes below the baseline. (B) From the edge of the wider message, Arabic or English. (C) See Standard Drawings for arrow dimensions. (D) (Height of sign - arrow height) *

2, use whole numbers.

These dimensions may be adjusted to comply with recommended heights and widths.

Example 900-02 Dimensions For Guide Signs Part 2 900-13


Example 900-03 Multiple Message Guide Signs

Part 2 900-14

ROADWAY DESIGN MANUAL – Roads and Bridges 1 of 14 904.07 STANDARD ARABIC SCRIPT FOR HIGHWAY SIGNS This section consists of pages numbered 1 through 14 of 14. The design of each letter and number is shown on a 5 mm grid in Figures 900.06 through 900.17. Letter shapes are shown when the letter occurs at the end of a word (or is unconnected), at the beginning of a word, and in the middle of a word (generally shown left to right respectively). The length of the connections to proceeding and following letters are included in the design. However, they may be increased slightly to maintain proper proportion with the English legend if it is larger than the Arabic legend. Letter height and spacing between words shall be detailed in the project drawings. Certain Arabic letters are not connected with letters which follow in the same word. The space between the letters and the letters which follow them are given in Figure 900.05.

Part 2 900-15

ROADWAY DESIGN MANUAL – Roads and Bridges 2 of 14

Figure 900.05 Guide Sign Letter Spacing

Part 2 900-16


Figure 900.06 Guide Sign Lettering Part 2 900-17























ROADWAY DESIGN MANUAL – Roads and Bridges 904.08 SIGN LIGHTING Roadway sign lighting shall be as recommended in AASHTO’s “An Informational Guide for Roadway Lighting”, 1984, pages 30-32. Sign Lighting shall be designed using medium ambient illuminance in accordance with the following table: Table 900.01 Sign Lighting Lighting Medium Ambient Levels Illuminance Illuminance 20-40 Fc Luminance 48-96 cd/m2

reflect general practices which may not always be applicable to Abu Dhabi. Where there are conflicts between this section, the Standard Drawings and the MUTCD, the guidelines in this section and the Standard Drawings should be followed, consistent with sound engineering practices and judgment. All pavement markings and symbols shall be thermoplastic per the Standard Drawings and the Standard Specifications. Typical urban layouts for pavement markings and raised pavement markers are shown in the Standard Plans. Raised pavement markers are generally not used in rural areas.

The uniformity (maximum) for the illuminance shall not exceed a ratio of 6:1, 4:1 is desirable.

905.02 TYPES OF PAVEMENT MARKINGS

904.09 SIGN LUMINARES

The following types of pavement markings shall be used, as required:

High-pressure sodium fixtures shall be used, 150 watt size. Each sign lighting shall be designed for mounting horizontally at the top of the sign panels, number and spacing of the fixtures shall be determined during design. Maximum spacing of the fixtures should not exceed 6 m. Sign lighting shall follow AASHTO recommendations. Independent design calculations are recommended using the design program Micro-Site-Lite, CALA or equivalent. The effect of adjacent roadway lighting on the sign should be considered in these calculations. Each fixture shall be individually fused in a NEMA 32 box at each sign structure. If a sign structure has four or more sign lights, two independent circuits shall be provided for that structure.

905

1. 2. 3. 4. 5. 6. 7.

Lane Markings Stop Line Markings Pedestrian Crossing Markings Channelization Markings Pavement Edge Markings Parking Space Markings Pavement Symbols (Arrows and Letters)

905.02.01

Lane Markings

In urban areas, markings separating traffic lanes in the same direction shall be comprised of type CR and type NR pavement markers spaced as shown on the Standard Drawings. Markings separating exclusive turning lanes from through traffic lanes shall be type NR pavement markers spaced as shown on the Standard Drawings from the stop bar to the end of the taper. In instances where two parallel and adjacent longitudinal lines are placed, they shall be 10 cm apart.

PAVEMENT MARKINGS

905.01 GENERAL Pavement markings shall be used for regulating, warning, and guiding road users. Discussion in this section is complimentary to the Manual on Uniform Traffic Control Devices (MUTCD) and shall be used in conjunction with that document. However, policies presenting in the MUTCD

For lane marking standards not shown in the Standard Drawings see Figure 900.18.

Part 2 900-29


Pavement Edge Markings

Pavement edges shall be marked only when there is no curb. The marking shall be a 10 cm wide continuous white line on the outside edge and a yellow line on the inside edge with corresponding type CR or YR pavement markings at 16.0 m intervals as shown on the Standard Drawings. 905.02.06

Parking Space Markings

Parking space markings shall be used wherever parking is allowed. They shall be 10 cm wide solid lines showing the borders of each parking space. 905.02.07

Arrows shall be used, as necessary, to indicate the types of movements, that can be made from the lanes where arrows are placed. They shall be solid, elongated, and 5.0 m long. The shape shall be as specified by international standards.

Figure 900.18 Lane Markings 905.02.02

Stop Line Markings

Stop line markings shall be continuous from curb to curb and shall be 30 cm wide as shown on the standard drawings. 905.02.03

Pedestrian Crossing Markings

Pedestrian crossings shall be marked by longitudinal stripes through the width of the pedestrian crossing which shall be 4.0 m. Stripes shall be 50 cm wide, with a 50 cm gap between adjacent stripes. The distance between the upstream edge of the pedestrian crossing and the beginning of the adjacent stop line shall be 1.0 m. 905.02.04

Pavement Symbols (Arrows and Letters)

Letters, whenever used, shall be solid, elongated, and 3.0 m long. The shape shall be as specified by international standards. Letter messages shall be both in Arabic and English.

906

MAINTENANCE OF TRAFFIC

During Construction, existing traffic flow will be maintained on paved, lighted detour roads. In general, detours will have two through lanes in each direction. 906.01 CONSTRUCTION STAGING Construction will be staged so as to avoid disruption of traffic flow as much as possible. When required and possible, pedestrian movements will be maintained by temporary sidewalks.

Channelization Markings

All channelization markings, except those mentioned above, shall be 20 cm wide solid lines. Dead areas created by channelization will have chevrons which shall be comprised of 20 cm continuous line.

Temporary pavement shall be used for all detours. Temporary lighting shall be provided during all stages of construction, including temporary detours.

Part 2 900-30

ROADWAY DESIGN MANUAL – Roads and Bridges 906.02 SAFETY MEASURES Standard barriers, barricades, signs, flashers and other protective measures will be provided for guiding, warning, and protecting vehicular and pedestrian traffic during construction. All road closures and construction traffic shall be coordinated with local police and fire services. 906.03 TEMPORARY TRAFFIC SIGNALS At locations of complex traffic movements, temporary and portable traffic signals will be used for the safe, orderly movement of traffic during construction. 906.04 MAINTENANCE PLANS

OF

TRAFFIC

A work phase plan shall be established by construction phases or sequence, indicating the duration of each phase or sequence. The plan shall include but not be limited to: • maintenance of traffic circulation during construction, • traffic control methods that need to be implemented, • construction detours, • Work areas per stage, • temporary barrier locations and details, • temporary signing and striping locations and details, • temporary construction quantities.

Part 2 900-31

ROADWAY DESIGN MANUAL – Roads and Bridges lighting enhances traffic safety through high visibility, the need for fewer poles, and greater flexibility in their location.

SECTION 1000 LIGHTING 1001 ROADWAY LIGHTING 1001.01

GENERAL

The main function of roadway lighting is to improve driver visibility. A well illuminated roadway increases safety by allowing drivers to identify potential hazards or conflicts. Well designed lighting allows the driver to quickly recognize roadway features such as alignment, delineation, intersections, ramps, traffic signs, traffic signals, and pedestrian crossings. The improved driving environment in turn improves traffic operations, capacity and safety. Lighting continuity is recommended for esthetic and functional reasons. Lighting continuity helps drivers identify roadway facilities and acts as a unifying design element. Lighting design responsibility generally encompasses entire roadways within the project limits. However, at the time of concept planning, the design responsibility may be reduced or expanded by the Municipality. The designer should consult the Road Section as to any variation in the design requirements. 1001.02

LIGHTING DESIGN CONSIDERATIONS

Freeways and Expressways Because freeways and expressways are wide and have higher traffic speeds, general street lighting requirements are inadequate for freeway and expressway lighting. High lumen lamps in conjunction with high mast poles are used to illuminate large roadway areas and reduce glare. Interchanges High mast lighting is ideal for illuminating interchanges and other large areas, because the illumination pattern is not confined to the basic driving lanes. High mast lights illuminate the entire interchange, creating the same overall view of the area as that perceived in daylight. High mast poles can be installed in suitably wide medians on multiple-lane roadways. This type of

Arterials and Frontage Roads Arterials serve moderately high volumes of traffic at lower speeds than freeways and expressways. Although their primary function is to move and maintain uninterrupted traffic flow, they frequently have busy at-grade intersections requiring traffic control devices. These at-grade intersections require greater visibility for traffic signals, signs and the resulting crossing and turning conflicts. Also, increased commercial development along arterials means increased pedestrian movements and possibly the need to accommodate public transportation (taxicabs and buses). Adequate lighting for pedestrian movements and public transportation’s frequent stopping, loading and unloading of passengers is vital to safety along arterials. Arterial lighting must also blend with commercial development lighting to avoid combinations which detract from the overall lighting or result in poor visibility. Sector Roads A sector roads primary function is to provide direct access to adjacent properties. Although traffic speed is low, traffic volume can be heavy and frequently interrupted especially in residential and commercially developed areas. Because of increased access to commercial and private property, sector roads, compared to arterials, must accommodate an even heavier volume of pedestrian movement. Lighting considerations are much the same as for arterials. Intersections and Pedestrian Crossings Lighting intersection and pedestrian crossings is of particular concern and must be adequate for traffic and pedestrian security, as well as meeting environmental objectives. If necessary for traffic safety, pedestrian security, or to enhance appearance, the lighting color should be varied to define the various elements more clearly. Generally, the illumination level at an intersection of two at-grade roadways is the sum of the illumination of the two roadways.

Part 2 1000-1


Roadway

Freeways & Expressways Interchanges

Table 1000.01 Illumination Requirements Minimum Uniformity Light Lantern Illumination Ratio Source (Lux) 22 2:1 HPS Cut-off Type III 22

2:1

HPS

22

2:1

Rectilinear, Sharp Cut-off

14

15*

3:1


10 ***

33

2:1


10-14

40**

2:1

HPS or MH HPS or MH HPS or MH Match Road

15

3:1


10

Sidewalks Away 10* From Road HPS - High Pressure Sodium MH - Metal Halide

3:1

HPS, or MH HPS

Decorative

4.6

Main Roads/ Arterials Sector Roads /Ramps Crosswalks Ramp Terminals &Traffic Conflict Areas Parking Areas

Cut-off Type V

Pole Height (m) 30.5

Cut-off Type

30.5 ***

30.5 *** or 14

Notes: 1. Lamps for sign lighting should be a different color from roadway. Mercury vapor lamps for sign lights will provide good contrast and easy differentiation from high pressure sodium roadway lighting. 2. Recommended illumination level indictates the minimum allowable. Individual designs shall specify lighting levels as advised by the Municipality/WED at the design phase. * ** ***

On high volume roads, lighting will be upgraded to suit conditions. Areas of traffic conflict would have high levels of illumination equal to the sum of values recommended for each of the intersecting roads. Use high mast with HPS on ramps wherever possible.

Rural Lighting Rural roadway lighting is generally warranted only at decision points such as interchanges or intersections. However, accident records should be examined to determine if poor visibility was a recurring factor. Continuous lighting on rural roadways may be considered early in the design process.

1001.03

ILLUMINATION REQUIREMENTS

Table 1000.01 summarizes the illumination requirements for various roadways. Illumination Illumination levels stated in Table 1000.01 represent the lowest average maintained levels considered appropriate for each kind of roadway or walkway in the various areas. Illumination

Part 2 1000-2

ROADWAY DESIGN MANUAL – Roads and Bridges criteria and calculations are based on the Illuminating Engineering Society’s (I.E.S.) standards modified to meet the higher uniformity and illumination levels required by the WED and the Municipality of Abu Dhabi. Uniformity Ratio A Uniformity Ratio (UR) is defined as the average maintained illumination of the roadway design area, divided by the lowest value at any point in the area. See Table 1000.01 for roadway criteria.

Lanterns mounted on 10 m poles shall be 400 watt high pressure sodium or metal halide lanterns. Lanterns shall have optical systems sealed against moisture, dirt and insects, and be mechanically strong and easy to maintain. Glare control for the mounting height specified, and cut-off characteristics shall be designed based on I.E.S. standards.

Light Source Light sources shall be as identified in Table 1000.01 and as modified during the design phase if advised by the Municipality. It is important that the lighting design be compatible with the surrounding area.

Lantern Mounting Height High mast lighting (30.5 m) is proposed for applicable interchanges and between closely spaced interchanges when conditions permit. On major thoroughfares not suitable for high mast lighting, but where substantial lighting requirements remain, pole heights would be 14m.

The roadways not identified in this manual will use a light source as directed by the Municipality. Side roads and ramps shall have the same light source as the adjacent main roads. Metal halide or high pressure sodium shall be selected to blend with the surroundings on sector roads.

High-mast lighting (30.5 m poles) shall be used on rural and urban freeways and expressways with wide medians where one row of 14 m poles is not suitable. The 30.5 m poles shall also be used at all interchanges. Wherever possible high mast lighting shall be used for ramps.

Lantern and Lamp Selection “Sharp cutoff” lanterns are proposed for roadway lighting per Table 1000.01. These lanterns are designed to illuminate a relatively large area without spilling light into adjacent areas. They produce uniform illumination and minimum glare.

High mast lighting will be used on main roads only when light height will not substantially interfere with nearby buildings. On other major thoroughfares, poles would be 14 m high and would be placed at the side or in the median of the roadway, as applicable. Single or multiple lanterns would be used to provide uniform illumination of the roadway.

High pressure sodium lamps provide excellent golden white color and enhance the esthetic qualities of concrete, stone and brick. Metal halide gives a whiter light, providing a color contrast to sodium lamps, and enhance the appearance of green and pastel colored materials. The lanterns shall be mechanically strong and easy to maintain. They shall be of adequate design to operate at mounting heights of 30.5 meters and able to withstand sustained wind speeds of 160 kph with 208 kph gusts. Lanterns mounted on 14 meter poles shall be 1000 Watt high pressure sodium, metal halide and mercury vapor lanterns cut-off, and provide efficient even illumination.

1002 PARKING AREA LIGHTING 1002.01

GENERAL

The function of light sources in parking areas is to give an overall view of the parking area and provide a measure of security. Lighting is also critical for vehicle maneuvers such as backing. 1002.02


Light source shall be high pressure sodium or metal halide selected to blend with the surroundings per Table 1000.01.

Part 2 1000-3


LANTERN MOUNTING HEIGHT

Ten meter high poles shall be used for all parking lot areas. Lantern configuration and light distribution shall be selected to suit the parking area geometry. 1002.04

LANTERN SELECTION

Lanterns shall be as detailed in the General Specifications and Table 1000.01.

1004 LIGHTING CONTROLS 1004.01

GENERAL

These items provide required electrical connections and controls to all roadway lighting, decorative lighting and street furniture lighting items (i.e. bus shelters, telephone booths and sidewalk lights). 1004.02

LIGHTING CONTROLLER REQUIREMENTS

1003 SIDEWALK LIGHTING 1003.01

Lighting shall be controlled by a 24 hour timing switch. Control cabinet requirements shall be as specified in the Standard Specifications.

GENERAL

Sidewalk lighting provides visually pleasant and decorative illumination to sidewalks adjacent to buildings, to buildings themselves and to the other pedestrian walkways.

1004.03

DESIGN STANDARDS AND PROCEDURES

Light source will be high pressure sodium per Table 1000.01 unless otherwise directed by the Municipality. Sidewalk lights will be provided only for the areas specifically advised by the Municipality.

Control cabinets should be located in the median where feasible. The maximum voltage drop in the outgoing circuits beginning at the control cabinet shall be four percent. Branching of underground cable circuits from all lighting units except 4.6 m poles will be allowed. There shall not be any intermediate joints in the lighting cable circuitry except the terminations in the lighting units or in the junction boxes.

1003.03

1005 POWER DISTRIBUTION

1003.02


LANTERN MOUNTING HEIGHT

Sidewalk light poles shall generally be 4.6 meters high with 2-100 watt high pressure sodium lanterns. However, special pole heights and lantern types may be required to meet special situations. The Project Design Manager should consult the Municipality as to the exact nature of the requirements at the time of concept planning. 1003.04

LANTERN SELECTION

Ornamental lighting of proper height for the pedestrian is proposed for sidewalks along buildings and in parks and landscaped areas. Low-level ground lights would be used to illuminate vegetation.

Electric service is 415/240 volts, three-phase, four-wire, 50 Hz system furnished by the Water and Electricity Department (WED). This service shall be provided at the lighting control cabinets. Underground distribution to the lighting units utilizes four conductor and steel wire armored XPLE insulated cables. Conductor size will be 25 mm2 for all 30.5 and 14 m light poles and 16 mm2 for all 10 and 4.6 m poles, street furniture and decorative lighting units. The lanterns will be connected in phase sequence to provide a balanced three-phase load.

Part 2 1000-4

ROADWAY DESIGN MANUAL – Roads and Bridges Type IV pull boxes shall be used adjacent to light pole foundations in paved areas except where interlocking pavers are used. They should be installed between the foundation race way conduit and the electrical conduit. Cables shall be direct buried under sidewalks and interlocking pavers used in parking areas except at the entry or exit of sector roads or parking areas where PVC ducts shall be provided. Cables under interlocking tiles at the entry or exit of sector roads and parking areas, shall be through concrete encased PVC ducts. All PVC conduits and ducts for underground cable lighting circuitry, shall be a minimum of 10 cm diameter. There should be a minimum of one spare duct at each crossing. Where lighting cables are proposed along the service reserves at road crossings, the available electrical ducts shall be used. Separate lighting road crossing ducts are not required at these locations. The underground lighting cables shall be installed along electrical service reserves in all possible cases. Wherever the lighting cables are proposed outside the service reserve, the cable route shall be immediately adjacent to the curb line. Separate earthing is required only at the terminal pole of each circuitry. All light poles and fixtures shall be earthed through the cable armoring.

1006 DESIGN AND SUPERVISION RESPONSIBILITIES The Municipality is responsible for the lighting criteria standards to light the roads. This criterion covers illumination levels, uniformity ratios and distribution and differences in brightness of the roadways. WED may suggest/advise of criteria or improvements in lighting for the Municipality and its Consultant to consider in design and construction. However, WED responsibility is limited to advising of its requirements for maintenance and access to the lighting poles and lanterns for inclusion in the Specifications. The Municipality and its Consultant are responsible for adherence to the lighting specifications. WED is responsible for the technical specifications and sizing for the electrical power supply for the lighting system including underground cable circuits, fuses, control cabinets, pull boxes and conduit. Accordingly, WED will be responsible for review of contractor submittals covering these items during the construction period. WED shall have the right to inspect such construction in the field and approval by WED shall be required prior to burial of the underground cable circuitry by the Contractor.

Part 2 1000-5

ROADWAY DESIGN MANUAL – Roads and Bridges The Agricultural Section will determine if a reservoir is required on a project. They will, also determine its location and size. However, final approval for including this work in a project must come from the Road Section.

SECTION 1100 ROADSIDE DEVELOPMENT 1101 LANDSCAPING Landscaping and the associated irrigation system for the roadside areas and medians will be designed by the Agricultural Section of the Abu Dhabi Municipality. The Design Project Manager is responsible for coordinating with the Agricultural Section to ensure that they are aware of the Project and its design schedule. Special permission from the Municipality is required for the removal of any green (planted) area. Newly created areas suitable for planting along with remaining green areas must be identified and presented on the General Plans. The Design Project Manager must provide these plans to the Agricultural Section so that they can design the new landscaping and irrigation system. Close coordination with the Agricultural Section is essential to ensure that the irrigation design is completed early enough to be incorporated into the Tender Documents of the roadway project. Agricultural planting areas should be shown on the general plans designated as green areas. Green areas within the residential sectors, (sectors predominantly villas or low rise structures), should be maximized while reducing paved areas. In general the green areas should be limited to the front portion of building plots. The areas between and behind the existing buildings should be paved with pedestrian or vehicular pavers as applicable. However, each sector must be considered individually. Local residents, Mosques, Embassies and/or some other significant feature within the sector, often require special (non-standard) treatment.

1102 IRRIGATION It may be required to design an irrigation reservoir with electrical and water services. In general, it will include the reservoir, pump-house structure and the incoming services, but will not include the interior piping, wiring or pumping systems.

1102.01

IRRIGATION DUCTS

All irrigation facility crossings of all roadways shall be accommodated within a duct. Duct details are included on the Miscellaneous Utility Detail Standard Drawings. Duct crossings should be located within allocated service reservation corridors. Guidelines for providing the irrigation ducts and appurtenances are: 1. Ducts for irrigation lines may be Glass Reinforced Plastic (GRP) or Polyvinylchloride (PVC) pipe conforming to the Standard Specifications. 2. Generally, ducts will be provided under the roadway at intersection crossings. Additional contingency ducts shall be located at spacing of approximately 250 to 300 meters between interchanges. Specific contingency duct requirements for each project must be coordinated with the Agriculture Department. Ducts under the roadway pavement must be aligned with each other in the median, both horizontally and vertically. 3. Ducts should normally have one meter of cover, however, one-half meter of cover is acceptable where positioning is due to conflicts with existing or proposed utilities. In superelevated sections, the ducts should have approximately the same degree of cross slope as the highway. All ducts should have a nominal (1%±) slope for drainage. 4. The end of ducts must extend 0.5 meters (minimum) past back face of curbs or sidewalks when in curbed situations. 5. The end of the ducts should extend into the verge area in an un-curbed condition. The intent is to maintain the cover from the

Part 2 1100-1

ROADWAY DESIGN MANUAL – Roads and Bridges sideslope at one meter (minimum) where the irrigation line comes out of sleeve.

uniform and visually pleasing design and appearance.

6. Ducts should be considered where maintenance roads and driveways cross irrigation lines.

In general, street furniture will only be provided in roadway projects at the direction of the Road Section. For urban interchange projects, installation of street furniture will be included as part of the proposed improvements. On rural interchange contracts, the extent of street furniture required could range from pedestrian signals to a full compliment of street furniture elements. On all types of projects, during the close of the Concept Phase, the Designer should consult with the Abu Dhabi Road Section to determine the types of street furniture that should be provided.

1103 FENCING The Designer and Abu Dhabi Road Section shall review fence requirements on a project specific basis.

1104 SLOPE PAVING Slope paving at bridge abutments shall conform to the Abu Dhabi Road Section Standard slope paving details. Where the mainline is depressed below the local crossroad, the slope paving shall approximate the typical cross section contours. A 6 meter grading transition at each edge of the slope paving should be indicated on the plans.

Descriptions of the basic function, elements, design standards and procedure for each street furniture item are included in following sections. 1106.02

DESIGN

Special treatment of slope paving may be applicable at specific locations. The Designer should coordinate slope paving treatments with the Abu Dhabi Road Section.

Details of street furniture have been designed and shown on the Standard Street Furniture Detail drawings and in the Standard Specifications. These details do not have to be revised from one contract to the other unless there is a projectspecific requirement.

1105 SWEET SAND COVERING

1106.03

In general, all proposed green areas shall be covered with a 30 cm minimum depth of sweet sand at the finish grade.

Benches provide resting facilities for pedestrians, much needed in Abu Dhabi in view of the warm climate. There are three types of benches designed for the Abu Dhabi Roadway Section projects, Type A, Type B and Type C.

The Designer shall calculate the quantity of sweet sand required for the project. The General Plan drawings will show the green areas included in the project.

1106 STREET FURNITURE 1106.01

GENERAL

Street furniture to be provided as part of the Abu Dhabi Roadway Section projects includes benches, bus shelters, telephone booths and sidewalk lighting. The purpose is to provide pedestrian amenities and to enhance the urban environment with street furniture that has a

BENCHES

1106.03.01 Type A bench This type of bench is comprised of two precast concrete ends and wood slats (over aluminum tubes), and does not have a backrest. The Type A bench is always used in combination with the Type B bench, except when it is used at taxi stops. 1106.03.02 Type B bench This type of bench includes a back rest, a planter and a waste receptacle. Basic elements of the bench itself are the same as the Type A bench,

Part 2 1100-2

ROADWAY DESIGN MANUAL – Roads and Bridges except for the back rest and higher ends. The Type B bench is also used in combination with a Type A bench to create a small gathering place for a group of people. 1106.03.03 Type C bench This type of bench is comprised of the same elements as a Type A bench except it is used only in bus shelters. Subject to space availability, basic criteria for placement of benches are as follows: 1. Two combination Type A/Type B benches are placed at every intersection, with each in different quadrant (preferably diagonal quadrants). 2. If space does not permit the above arrangement, a Type B bench is placed in the same fashion. 3. At least two Type B benches are placed at each side of the main road between two intersections. 4. Two Type C benches are placed within each bus shelter (considered as part of and paid under bus shelters). 5. One Type A bench is placed at each taxi stop. 1106.04

BUS SHELTERS

Bus shelters are to be placed at every bus stop except where space limitations prohibit their use. They are to be located at the far (downstream, according to the direction of traffic) end of the bus stop with one meter from the edge of the curb. 1106.05

TELEPHONE BOOTHS

Foundations for telephone booths will be provided in road projects, the telephone booth and operating equipment are the responsibility of Etisalat. Etisalat determines locations and quantity of telephone booths to be included in each Contract as approved by the Road Section.

1107 NOISE ABATEMENT The Designer and the Abu Dhabi Road Section shall review any noise abatement requirements on a project specific basis. In general, the Designer is to mitigate, as much as possible, any increase in the traffic noise, especially in residential neighborhoods. In special circumstances involving sensitive areas, depressed roadways or noise abatement walls may be required.

Bus shelters are placed on bus stop sidewalks to provide shade and seating for bus passengers.

Part 2 1100-3

ROADWAY DESIGN MANUAL – Roads and Bridges AASHTO—American Association of State Highway and Transportation Officials Standard Specifications for Highway Bridges, 15th Edition -1992, including all Interim Specifications to date.

PART 3 STRUCTURE DESIGN SECTION 100 DESIGN CRITERIA 101 101.01

Approval—Approval as obtained from the Abu Dhabi Roads Section Project Manager.

GENERAL

Drainage Report—The Drainage Report as produced by the Bridge Drainage Section or, when applicable, by a consultant.

PURPOSE

The purpose of this section is to provide Bridge Design Criteria in order to establish a uniform project design and construction policy that will aid the Consultant in the preparation of final design, plans and specifications, and insure safe and uniform structural capacity throughout the project. Structures shall be designed in accordance with the latest edition, including revisions, of the Standard Specifications for Highway Bridges published by the American Association of State Highway and Transportation Officials (AASHTO) and the Structural Design Standards included herewith in Part 3 of this Roadway Design Manual. The design shall be based on the latest edition of the AASHTO specifications as existing on the date of the design contract. The Structural Design Standards presented hereunder shall govern over the AASHTO Specifications wherever the are “At Variance With” or “In Addition To” the AASHTO Specifications. These criteria set forth minimum standards. The Consultant may propose more conservative criteria if, in his judgment, such criteria are required. However, all deviations from the criteria must be justified and receive prior approval from the Abu Dhabi Roads Section Project Manager. 101.02

DEFINITIONS

The following definitions and abbreviations are provided to clarify usage of terms and to avoid the need for excessive verbiage.

Geotechnical Report—The Geotechnical Report including the Foundation Design Report as produced by the Geotechnical Section or by a consultant. Special Provisions—The Special Provisions to the Standard Project Specifications as specifically written for each individual project. Standard Specifications—The Standard Project Specifications AASHTO Specifications for Structural Supports—The AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals, latest Edition. 101.03

BRIDGE TYPES

Bridge Definition—“A ‘Bridge’ is defined as a structure including supports erected over a depression or an obstruction, as water, highway or railway and having a track or passageway for carrying traffic or other moving loads and having an opening measured along the center of the roadway of more than 6.00 meters between undercopings of abutments or springlines of arches or extreme ends of openings for multiple boxes; it may include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening.” Bridge—The term “bridge” is usually reserved for structures over water courses or canyons. Overpass—A structure carrying the principal route over a highway street or railroad.

Part 3 100-1

ROADWAY DESIGN MANUAL – Roads and Bridges Underpass—A structure which provided for passage of the principal route under a highway, street, railroad or other feature. Traffic Interchange—An overpass or underpass is also called a T.I. if on and off ramps are provided to the intersecting roadway. Viaduct—A structure of some length carrying a roadway over various features such as streets, waterways or railroads. Tunnel—A structure carrying a roadway through a hill or mountain. Pedestrian Overpass—A structure carrying a pedestrian walkway over a roadway. Pedestrian Underpass—A structure which provides for passage of a pedestrian walkway under a roadway.

102 102.01

DESIGN FEATURES GENERAL

The general features of design shall be as specified in Section 2 of AASHTO except as clarified or modified in this manual. 102.02

Highway Traffic Structures

The design vertical clearance to structures passing over Freeways, Highways and all Rural and Urban Arterials shall be at least 6.00 meters over the entire roadway width, including auxiliary lanes and shoulders. An allowance of 150 millimeters is included to accommodate future resurfacing. This allowance may be waived if the roadway under the structure is surfaced with portland cement concrete. The design vertical clearance to structures passing over all other highways and streets shall be at least 5.50 meters over the entire roadway width, including auxiliary lanes and shoulders. An allowance of 150 millimeters is included to accommodate future resurfacing. This allowance may be waived if the roadway under the structure is surfaced with portland cement concrete. Certain routes have been designated as truck routes. On these routes, larger vertical clearance must be maintained. For future projects, these routes will be identified by the Abu Dhabi Roads Section Project Manager during the concept stage. 102.03.02

Pedestrian Overpasses

Because of their lesser resistance to impacts, the minimum design vertical clearance to pedestrian overpasses shall be 6.00 meters regardless of the highway system classification. An allowance of 150 millimeters is included to accommodate future resurfacing.

DESIGN METHODS

ALL BRIDGE MEMBERS ARE TO BE DESIGNED IN ACCORDANCE WITH AASHTO AND THE REQUIREMENTS OF THIS MANUAL. (Other standards may be allowed with Department approval.) 102.03

102.03.01

102.03.03

VERTICAL CLEARANCE AT STRUCTURES (AASHTO 2.2.3)

The following are minimum vertical clearance standards for highway traffic structures, pedestrian overpasses, railroad overpasses, tunnels and sign structures. Lesser clearances may be used only under very restrictive conditions, upon individual analysis and with the approval of the Abu Dhabi Roads Section Project Manager.

Railroad Overpasses

Structures over railways shall provide a minimum clearance of 7.00 meters above top of rail, except that overhead clearance greater than 7.00 meters may be approved when justified on the basis of railroad electrification. No additional allowance shall be provided for future track adjustments.

Part 3 100-2


Tunnels

102.06

The minimum design vertical clearance for tunnels shall be at least 6.00 meters for freeways and arterials and at least 5.50 meters for all other highways and streets. 102.03.05

Sign Structures

Because of their lesser resistance to impacts, the minimum design vertical clearance to sign structures shall be 6.00 meters regardless of the highway system classification. An allowance of 150 millimeters is included to accommodate future resurfacing. 102.03.06

Width (AASHTO 2.3.1)

The horizontal clear width for rural bridges where approach guardrail is used shall provide an additional width on each side of the approach roadway width to allow the bridge rail to line up with the approach guardrail. The horizontal clear width for urban bridges, in which curb and gutter and/or sidewalks are used, shall equal the approach roadway width. 102.04

RAILINGS (AASHTO 2.7)

In general, concrete barrier should be used as a vehicular railing. For situations requiring a different barrier type, only FHWA crash test approved bridge rails are allowable alternatives. Bridge rails shall be constructed vertical. Concrete barriers shall not be slipformed. For cast-in-place, post-tensioned concrete bridges, barriers shall be cast after post-tensioning and may be cast before falsework removal. 102.05

CONCRETE BARRIER TRANSITIONS

Transitions from bridge concrete barrier to approach guardrail should, when practical, be located on the bridge, approach slab or wingwalls.

APPROACH SLABS

Concrete approach slabs shall be used on all structures. Approach slabs serve a dual purpose of providing a transition structure from the bridge to the approach roadway should the roadway embankment settle and of eliminating the live load surcharge of the abutment backwall when the conditions specified in AASHTO 3.20.4 are satisfied. Approach slabs are to be designed using the Service Load Design Method and shall cover the entire roadway width including the shoulders, from wingwall to wingwall. 102.07

ANCHOR SLABS

When approach roadways are paved with portland cement concrete pavement (PCCP), adequate means shall be provided to prevent pavement growth from causing damage to the bridge. Use of a properly designed anchor slab is one means of providing such protection 102.08

DECK DRAINAGE

On grade separation structures, roadway drains shall not discharge water onto unprotected embankment slopes or within five meters of the traveled roadway below, nor shall drains be located less than 1.5 meters from the centerlines of abutments or piers. In urban areas collection of deck drainage in a pipe system may be required, with down drains in or on pier columns discharging into storm drainage collector systems. Consideration should always be given to provide collector drains and discharge systems on the approach roadway gutter rather than on the bridge. For bridges with sidewalks, expansion joints shall be turned up at the curb line to prevent roadway water from entering sidewalk areas. Appropriate means shall be taken to ensure that sidewalk drainage does not pond and that the water does not escape around the wing walls and erode the embankment. For deck drainage design criteria, refer to the ROADWAY DESIGN MANUAL - Drainage.

Part 3 100-3


WING WALLS

102.12

Wing walls shall extend 1.50 meters beyond the catch point, where catch point is defined as the intersection of the fill slope in front of the abutment with the finished approach grade at the outside face of the wing wall. The bottom of the wing walls shall be embedded a minimum of 1 meter into the approach fill at the end of the wing walls. 102.10

Maximum flexural crack width at the tensile face of a reinforced concrete section shall not exceed 0.25mm for normal conditions of exposure and 0.20mm for marine and unfavorable conditions of exposure (such as alternate wetting and drying, humid atmosphere, direct contact with soil, etc.). The allowable crack width can be increased by 25% under earthquake/wind/temporary construction conditions.

LIGHTING 102.13

Consideration shall be given to special lighting above and below the structure. This lighting shall serve as ornamental lighting to enhance the aesthetics and also to enhance safety. This lighting is in additional to the normal roadway lighting. Refer to the lighting section of this manual for roadway lighting criteria. Coordination of all structure lighting with existing and/or planned lighting of connecting and adjacent roads must be considered.

CORROSION PROTECTION (AASHTO 8.22)

Due to the adverse corrosive environment, all reinforced concrete structures shall use epoxy coated rebar unless otherwise directed by the Project Manager.

103

103.01 102.11

CONCRETE CRACK CONTROL

ARCHITECTURAL CONSIDERATIONS PROCEDURE

BRIDGE DECK ELEVATIONS

The project design group shall prepare either computer plotted contours at 0.1 meter intervals at a 1:50 scale or tabulate elevations at 3.0 meter intervals along the profile grade line, with additional elevation points on each perpendicular (radial) such that the bridge can be completely covered with 0.1 meter contours. The number of elevation points on each perpendicular must be such that the lowest, or the highest, point is outside the bridge for use by the construction supervision staff to help check the contractor’s geometric layout.

Following the approval of the civil and basic structural concepts for an interchange, including configuration, alignment, profile and pier locations, the Project Design Manager will meet with the Structural, Architectural, and Graphics Design Managers to develop basic alternatives and set architectural design parameters. Environmental constraints and influences will be established. The Concept Design Team will determine the number of structural concepts and architectural options to be studied. The purpose of these studies will be do develop applicable concepts and options in the form of presentation displays, to be used as a basis for the Abu Dhabi Roads Section review and decision making. The approved displays are submitted to the Abu Dhabi Roads Section for review and selection of the desired alternative. The approved scheme the will progress to the preliminary and final design phases.

Part 3 100-4


GENERAL CRITERIA

Every effort should be made in the treatment of structures to respect the Islamic design and culture. Design concepts should be easily implemented. Construction considerations are also taken into account in the architectural treatment concepts. Architectural elements should be functional, durable and easily maintained. Each structure should have individuality; however, a totally different design is not required for each structure. It is desirable to maintain a sense of continuity throughout the whole program. Architectural treatment should be continuous through an interchange. In the downtown area, underpasses spanning a given roadway should have similar treatment to establish continuity. Decorative and median lighting should be similar on overpasses along a given route.

Part 3 100-5


SECTION 200 DESIGN LOADS 201 201.01

201.06

1. Highway Bridge Live Load: AASHTO 20-44

LOAD TYPES

2. 3. 4.

GENERAL

Loads shall be as specified in Section 3 of AASHTO except as clarified or modified in this manual. 201.02

STRUCTURE LOADINGS

5. 6. 7.

DEAD LOADS (AASHTO 3.3.1)

increased by 25 percent. Wind Velocity: 160 kilometers per hour. Humidity Range: 25 percent to 100 percent. Earth Pressure: For specific project recommendations, refer to Soils Report Future Utilities: 75 kg/m² of Bridge Deck. Earth Weight: 1920 kg/m3 Earthquake Loading: Only to be considered if directed by the Road Section Project Manager.

Utility loads shall be included as applicable. 201.07 201.03

FUTURE WEARING SURFACE (AASHTO 3.3.3)

All new structures shall be designed to carry an additional dead load of 120 kg/m2 from curb to curb of roadway to allow for a future wearing surface. This load is in addition to any wearing surface which may be applied at the time of construction. The weight of the future wearing surface shall be excluded from the dead load for deflection calculations. 201.04

WEARING SURFACE (AASHTO 3.3.5)

Friction forces due to elastomeric bearing pads or TFE surfaces shall be based on the Manufacturer’s data for the bearing used. 201.08

THERMAL FORCES (AASHTO 3.16)

1. Temperature Range: 70ºC. 2. Temperature Fall: 30ºC to 0ºC = 30ºC. 3. Temperature Rise: 30ºC to 70ºC = 40ºC. 4. The temperature gradient between the top slab and bottom slab of concrete box girder bridges is 20ºC.

The top 15 millimeters of the deck shall be considered as a wearing surface. The weight of the wearing surface shall be included in the dead load but the 15 millimeter shall not be included in the depth of the structural section for all strength calculations including the deck, superstructure and the pier cap, where appropriate. 201.05

FRICTION FORCES (AASHTO 3.9.2)

HIGHWAY LOADS (AASHTO 3.7.1.1)

P Loads (permit design live loads) are special vehicular loads that will be applied only to specific structures, such as interchange ramps, and at the direction of the Abu Dhabi Roads Section.

201.09

STREAM FORCES (AASHTO 3.18.1)

A Drainage Report shall be produced by Bridge Drainage Section or a consultant, when appropriate, for all stream and/or channel crossings. The designer should review the Drainage Report for a full understanding of waterway considerations. The report should contain as a minimum, the following information for both the critical flow and superflood conditions: • • • • • • •

Part 3 200-1

High water elevation Mean Velocity Scour Elevations (General and Local) Angle of attack Required bank protection Special drainage considerations Horizontal and Vertical Clearances

ROADWAY DESIGN MANUAL – Roads and Bridges •

Direction of Flow

For design for the most critical flow and the superflood condition, the following criteria shall be used unless more severe criteria is recommended in the Drainage Report. Design calculations of stream forces on piers over natural water courses shall assume a 0.6 meter increase in pier width per side due to blockage by debris with a shape factor k = 1.40 for the first 3.5 meters of depth. For flows with depths greater than 3.5 meters, only the top 3.5 meters shall be assumed blocked by debris with lower sections using the actual pier width and a shape factor in accordance with AASHTO. For uncased drilled shafts, a 20% increase in diameter should be assumed to account for possible oversizing of the hole and any irregular shape. The force distribution on the pier shall be assumed to vary linearly from the value at the water surface to zero at the bottom of the scour hole as described in AASHTO. When the clear distance between columns or shafts is 5.00 meters or greater, each column or shaft shall be treated as an independent unit for stream forces and debris. When the clear distance is less than 5.00 meters the greater of the two following criteria shall be used: 1) Each column or shaft acting as an independent unit or 2) All columns or shafts acting as one totally clogged unit with 0.6 meters of debris normal to the flow added on each end. The average main channel velocity for the appropriate flow condition shall be used in calculating the stream forces. The water surface elevation shall be the high water elevation for the appropriate flow condition. A minimum angle of attack of 15 degrees shall be assumed. Scour may be categorized into two main types: general and local. General scour is the permanent loss of soil due to degradation or mining while local scour is the temporary loss of soil during a peak flow. Local scour may consist of two types: contraction scour and local pier or abutment scour. Contraction scour occurs uniformly across

the bridge in the stream width. Local pier and abutment scour occurs locally at substructure units due to the turbulence caused by the presence of the substructure unit. Bridges over natural water courses shall be investigated for four different streambed ground lines. Refer to Figure 200.01 for an illustration of these cases. Case 1 represents the “as-constructed” stream cross section. For this case, the bridge shall be designed to withstand the forces from the AASHTO Groups I to VII load combinations. Case 2 represents the long term dry streambed cross section, i.e. the “as-constructed” stream cross section minus the depth of the general scour. For this case, the bridge shall be designed to withstand the same forces as for Case 1. The requirements contained in AASHTO 4.4.5.2 need not be met. Case 3 represents the streambed cross section condition for the most critical design flow. Abutment protection is designed to withstand this event and abutments may be assumed to be protected from scour for this condition. Piers will experience the full general and critical flow local scour. For this case, the bridge shall be designed to withstand the forces from the AASHTO Groups I to VI load combinations. Case 4 represents the streambed cross section conditions for the superflood condition. For this case, all bank protection and approach embankments are assumed to have failed. Abutments and piers should be designed for the superflood scour assuming all substructure units have experienced the maximum scour simultaneously. For this case, the bridge shall be designed to withstand the following forces: DL + SF + B + 0.5W. For members designed using the WSD Method an allowable overstress of 140% shall be used. For members designed using the LFD Method a gamma factor of 1.25 shall be used.

Part 3 200-2


Figure 200.01 Groundline Variations Due to Scour

201.10

Roads Section Project Manager, a minimum differential settlement of 25mm may be used in the design.

LATERAL EARTH PRESSURE (AASHTO 3.20.1)

For backfills compacted in conformance with the Standard Specifications, active pressure for unrestrained walls should be calculated using an internal angle of friction of 33 degrees unless recommended otherwise in the Geotechnical Report.

Differential settlement, if required, shall be considered the same as temperature and shrinkage forces and included in Group IV, V and VI load combinations. 201.12

201.11

DIFFERENTIAL SETTLEMENT (AASHTO 3.3.2.1)

Differential settlement shall be considered in the design when indicated in the Geotechnical Report. The Geotechnical Report should provide the magnitude of differential settlement to be used in the design. If not addressed in the Geotechnical Report, and at the direction of the

EARTHQUAKES (AASHTO 3.21)

Earthquake criteria will only be considered in the design process at the direction of the Road Section Project Manager. If so directed, reference is made to AASHTO Division 1-A.

Part 3 200-3


DISTRIBUTION OF LOADS

Loads shall be distributed as specified in Section 3 of AASHTO except as clarified or modified in this manual. 202.01

In calculating bending moments in multi-beam precast concrete bridges, conventional or prestressed, no longitudinal distribution of wheel load shall be assumed. The live load bending moment for each section shall be determined by applying to the beam the fraction of a wheel load (both front and rear) determined by the following relations:

SUPERIMPOSED DEADLOAD DISTRIBUTION (AASHTO 3.23.2.3.1.1)

The weight of curbs, barriers and sidewalks for an I-Girder bridge with composite concrete deck shall be distributed as follows:

Load Fraction = S D Where

i) Equally over all girders ii) Equally over all girders under the sidewalk iii) If there is no sidewalk, curb and barrier shall be distributed 60% to the exterior girders and 40% to the interior girders. Each girder shall be designed for the condition that causes highest stresses. Girders shall in no way be designed for loads less than that specified in AASHTO Section 3. 202.02

D = 5 + NL + ( 3- 2NL ) ( 1-C ) 2 when C<3 10 7 3 D = 5 + NL when C>3 10 NL = total number of traffic lanes from AASHTO Article 3.6

CONCRETE BOX GIRDERS (AASHTO 3.23.2.3.2.2)

In calculating the number of lanes of live load on the superstructure, the entire cross section of the superstructure shall be considered as one unit with the number of lanes of live load equal to the out-to-out width of the deck in meters divided by 4.27. Do not reduce this number for multiple lanes as specified in AASHTO 3.12.1 nor round to a whole number as specified in AASHTO 3.6.3. 202.03

S = 12 NL + 9 Ng

Ng = number of longitudinal beams C = K(W/L), a stiffness parameter W = overall width of bridge in meters L = span length in meters Values of K To Be Used in C = K(W/L) Bridge Type Multi-Beam

PRESTRESSED VOIDED SLABS (AASHTO 3.23.4.3)

The equations for distribution of live load contained in the Fifteenth Edition (1992) including the 1993 and 1994 Interims shall not be used. The new distribution factors in the latest edition, initially changed in the Fourteenth Edition (1989), are based on tests on T-beams and are not deemed appropriate for voided slabs or box beams. Instead, the equations in the Thirteenth Edition (1983) as repeated below shall be used to distribute live loads:

202.04

Beam Type Non-Voided Rect Rect. w/ Circular Voids Box Section Channel

K 0.7 0.8 1.0 2.2

PRESTRESSED BOX BEAMS (AASHTO 3.23.4.3)

The equations for distribution of live load contained in the Fifteenth Edition (1992) including the 1993 and 1994 Interims, shall not be used. Refer to Distribution of Loads in Section 202.02 of this manual for criteria on distribution of loads.

Part 3 200-4

ROADWAY DESIGN MANUAL – Roads and Bridges 1. γ(Gamma) Factor

202.05 LATERAL TENSIONING OF MULTI-BEAM UNITS (AASHTO 3.23.4.1) Each lateral tensioning tie shall consist of a 38 millimeter diameter mild steel bar tensioned to 13,560 kg. Tension in the 38 millimeter diameter mild steel should be applied by the turn of nut method. The designer should determine the number of turns of the nut required to achieve the 13,560 kg force. This value should be shown on the plans. A36M steel bars for the tie normally come in 6 meter lengths. the final total length of the tie should be made using threaded couplers; not welded splices. When couplers are used, the hole through the diagram should be increased from the normal 64 millimeter to 102 millimeter diameter to accommodate the couplers.

The γ (gamma) factor is the most basic of the three. It varies in magnitude from one load combination to another, but it always applies to all the loads in a combination. Its main effect is stress control that says we do not want to use more than about 0.8 of the ultimate capacity. Its most common magnitude, 1.3 lets us use 77%. Earthquake loads are not factored above 1.0 because we recognize that stresses in the plastic range are allowed, as long as collapse does not occur. An example may be given to justify the use of gamma of 1.3 for dead load. Assuming the live load being absent, the probable upper value of the dead load could be a minimum of 30% greater than calculated. For a simple structure this percentage may be as follows:

Adequate means shall be used to ensure that the ties are adequately protected from corrosion. the rod, nut and bearing plate shall be galvanized in accordance with ASTM A153 (AASHTO M232). 202.06

10% 5% 5% 10% 30%

LIVE LOAD DISTRIBUTION (AASHTO 3.6.3 AND 3.12.1)

due to excess weight. due to misplaced rebar structure behavior approximation stress increase (actual vs. calcs.) Total variation assumed to occur concurrently at the section most heavily stressed.

2. β (Beta) Factor In designing the superstructure, the live load distribution factors shall not be reduced for multiple lanes as specified in AASHTO 3.12.1 or rounded to a whole number as specified in AASHTO 3.6.3. These two reductions apply to substructure design only.

203

LOAD FACTORS

An essential feature of Load Factor Design (LFD) requires raw design loads or related internal moments and forces to be modified by specified load factors (γ, gamma and β, beta), and computed material strengths to be reduced by specified reduction factor (φ, phi). These are safety factors which ensure certain margins for variation. The three different kinds of factors are each set up for a distinct purpose, each independent of the other two. In this way, any one of them may be refined in the future without disturbing the other two.

The second factor, β(beta), is a measure of the accuracy with which we can predict various kinds of loads. It also reflects the probability of one load’s simultaneous application with others in a combination. It applies separately, with different magnitudes, to different loads in a combination. For example, it is usually 1.0 for dead load. It varies from 1.0 to 1.67 for live loads and impact. Due regard has been given to sign in assigning values to beta factors, as one type of loading may produce effects of opposite sense to that produced by another type. The load combinations with βD=0.75 are specifically included for the case where a higher dead load reduces the effects of other loads.

Part 3 200-5

ROADWAY DESIGN MANUAL – Roads and Bridges The beta factors for prestressing force effects are set so that when multiplied by the respective gamma factor, the product is unity. Beta of 1.67 for live load plus impact from H loads reflects AASHTO’s way of handling permit loads. 3. φ (Phi) Factor φ(phi), the third factor, relates to materials and is called either a capacity reduction factor or a strength reduction factor. Its purpose is to account for small adverse variations in material strength, workmanship, and dimensions. It applies separately to different magnitudes for various load effects in reinforced concrete, and various manufacturing processes in prestressed concrete. Since φ relates to materials rather than loads, its values are given in the various material specifications. For structural steel it is almost always 1.0. For concrete it varies from 0.7 to 1.0.

Part 3 200-6


SECTION 300 REINFORCED CONCRETE 301

301.03

GENERAL

Reinforced concrete design criteria shall be as specified in Section 8 of AASHTO except as clarified or modified in this manual. 301.01

CONCRETE (AASHTO 8.2)

Concrete for highway structures shall have the following minimum cylinder strengths, unless otherwise directed by the Project Manager: Decks except barriers Abutments Piers except footings Drilled Shafts All other

f ′c = 280 kg/cm2 f ′c = 210 kg/cm2 f ′c = 280 kg/cm2 f ′c = 280 kg/cm2 f ′c = 210 kg/cm2

In accordance with the applicable provisions of AASHTO, the Strength Design Method (LFD) shall be used for the design of all reinforced concrete members except where such members are to be below grade or intended for water retention, then the Service Load Design Method shall be used. 301.04

•

Deformed Round Steel Bar Reinforcement, AASHTO M 31M Grade 400 fy = 4 080 kg/cm2 fu = 6 120 kg/cm2 fs = 1 680 kg/cm2 T or C in beams Es = 2 039 470 kg/cm2

Class K 250 Concrete Design Parameters f ′c = 210 kg/cm2 fc = 80 kg/cm2 Ec = 220 000 kg/cm2

•

•

Steel Wire used as Spirals, AASHTO M 32 Welded Wire Fabric used as reinforcement in concrete and mortar, AASHTO M 55


301.02

Spiral Reinforcement and Welded Wire Fabric Steel Bars used as Spirals, AASHTO M 31M Grade 400


•

REINFORCEMENT (AASHTO 8.15.2.2)

Concrete shall be reinforced only with fusion bonded epoxy coated reinforcement steel conforming to AASHTO M 31M (ASTM A615M) Grade 400 as follows:

For Design Load use Concrete Weight = 2500 kg/m3 •

DESIGN METHODS (AASHTO 8.14.1)

302

DIAPHRAGMS (AASHTO 8.12.3)

Reinforced concrete box girder diaphragm criteria shall be the same as for post-tensioned box girders as specified under Diaphragms in Section 402.06 of this manual.

SLAB DESIGN

Slabs shall be designed in accordance with the criteria specified in Section 3 of AASHTO except as clarified or modified below. All reinforcing bars are to be epoxy coated bars. All reinforcing bars shall be straight bars top and bottom. The use of truss bars will not be permitted.

Part 3 300-1

ROADWAY DESIGN MANUAL – Roads and Bridges For skews less than or equal to 20 degrees transverse bars shall be placed parallel to skew. For skews greater than 20 degrees transverse bars shall be placed normal to girders.

the the the the

Use of steel stay-in-place forms should be considered during design for steel girder or precast girder bridges for special conditions only. Some circumstances which warrant such investigation include: bridges over heavily traveled roads, bridges over live streams and bridges over deep canyons. A discussion on their use shall be made in the Design Concept Report. If use of steel stay-in-place forms is not recommended during design, they will not be allowed during construction due to the extra dead load. Contractor requests for usage during construction will not be approved. 302.01

SPAN LENGTHS (AASHTO 3.24.1.2)

The deck slab span length for AASHTO girders shall be the clear distance between the top flanges plus one-half the flange width. 302.02

302.03

The minimum clearance for top reinforcing in new decks shall be 50 millimeters with 50 millimeter Asphaltic wearing surface and the minimum specified concrete strength (f ′c) shall be 280 kg/cm2. 302.04

302.05

1.800 2.100 2.400 2.700 3.000 3.300 3.600 3.900

RAILING LOADS (AASHTO 3.24.5.2)

When barriers are located at the deck edge, the deck shall be designed to resist both the axial force and the bending moments due to all dead loads and horizontal rail load or due to all dead loads plus vertical wheel loads, whichever is critical.

The thickness of new deck slabs shall be designed in 10 millimeter increments with the minimum thickness as shown below, unless otherwise directed by the Project Manager.

Up to 1.801 to 2.101 to 2.401 to 2.701 to 3.001 to 3.301 to 3.601 to

DISTRIBUTION METHOD (AASHTO 3.24.3)

Use the AASHTO method for load distribution on slabs except for unusual loads or unusual structures such as single cell boxes.

SLAB THICKNESS (AASHTO 8.11.1)

Slab Thickness S(m)

PROTECTION AGAINST CORROSION (AASHTO 8.22.1)

t(mm) 190 200 210 220 230 240 250 260

Where S = Design span as defined in AASHTO 3.24.1 and above. t = Minimum thickness of deck slab.

Part 3 300-2


SECTION 400 PRESTRESSED CONCRETE 401 401.01

401.02

ALLOWABLE STRESSES— CONCRETE (AASHTO 9.15.2.2)

The maximum allowable tensile stresses in a precompressed tensile zone at service load after losses have occurred shall be in accordance with AASHTO except as modified below:

DESIGN CRITERIA GENERAL

Prestressed design criteria shall be as specified in Section 9 of AASHTO except as clarified or modified in this manual. Members shall be designed to meet both Service Load Design and Strength Design (Load Factor Design) criteria as specified in AASHTO. Prestressing steel for precast prestressed members and cast-in-place post-tensioned members shall be 12.50 millimeter diameter "Uncoated Seven-wire High Tensile Cold Drawn Low Relaxation Strand for Prestressed Concrete" as specified in ASTM A416, Grade 270 with f ′c = 18 360 kg/cm2 and Eps = 2 039 470 kg/cm2. Use of 15.20 millimeter diameter strand is allowed for cast-in-place post-tensioned members only. The yield point stress of prestressing steel, f*y, may be assumed equal to 0.90 f ′c for low relaxation strand. Prestress losses shall be calculated in accordance with AASHTO Article 9.16.2.1. The estimated losses contained in Table 9.16.2.2 and Article 9.16.2.2 shall not be used. Section properties shall be based on gross area of members. Use of the transformed area of bonded reinforcement shall only be used for unusual structures and only when approved. Web reinforcement for shear shall consist of rebars; not welded wire fabric. The minimum top cover for slab reinforcement specified in AASHTO Article 9.25.1.2.1 shall be 50 millimeters with 50 millimeter Asphaltic wearing surface.

Tension Load Condition Stress Girder DL + Prestress Total Service Load

401.03

Allowable 0 0.8 ƒ 'c

SHEAR (AASHTO 9.20)

Shear design shall be in accordance with Ultimate Strength Design Method contained in the latest AASHTO Specifications. Prestressed concrete members shall be reinforced for diagonal tension stresses. Shear reinforcement shall be placed perpendicular to the axis of the member with spacing not-toexceed three-fourths the depth of the member. The critical sections for shear in simply supported beams will usually not be near the ends of the span where the shear is a maximum, but at some point away from the ends in a region of high moment. For the design of web reinforcement in simply supported members carrying moving loads, it is recommended that shear be investigated only in the middle half of the span length. The web reinforcement required at the quarter points should be used throughout the outer quarters of the span if the critical shear section is included within the design section. For continuous bridges whose individual spans consist of precast prestressed girders, web reinforcement shall be designed for the full length of interior spans and for the interior three-quarters of the exterior span and based on the critical shear design section.

Expansion and contraction design criteria shall be as specified in Part 3, Section 600 of this manual.

Part 3 400-1


normal to girder for sloping exterior webs). Interior webs shall be constructed vertical.

POST TENSIONED BOX GIRDER BRIDGES

402.06

GENERAL

Post-Tensioned Box Girder Bridges shall be designed in accordance with AASHTO specifications. Girders shall be designed by Working Stress Method and checked by the Ultimate Strength Method (Load Factor Design). The deck slab is to be designed by the Working Stress Method. 402.02

CONCRETE (AASHTO 9.2 AND 9.22)

The following concrete strengths are the desired strengths to be used. Higher strengths may be used if approved by the Abu Dhabi Roads Section Project Manager. Initial

f ′c = 290 kg/cm minimum.

Final

f ′c = 350 kg/cm2 minimum f ′c = 420 kg/cm2 maximum

402.03

2

BEARING PADS

Allow an extra 80mm movement per 100 meters of girder length for long-term creep and shortening due to post-tensioning. 402.04

CREEP AND SHRINKAGE (AASHTO 9.4)

For restrained members in continuous bridges where shortening due to post-tensioning induces moments and shears, a shrinkage and creep coefficient of 1.5 shall be used for design of substructure elements with the total movement equal to 1.5 times the initial shortening. For superstructure elements, no creep factor should be applied except for long term deflection considerations. 402.05

FLANGE AND WEB THICKNESS - BOX GIRDERS (AASHTO 9.9)

A single 250 millimeter thick intermediate diaphragm shall be placed at the midspan for all bridges. Special consideration for additional diaphragms should be given to box girders with large skews, curved boxes and boxes over 2 meters in depth. Diaphragms shall be placed parallel to abutments and piers for skews less than or equal to 20 degrees and normal to girders and staggered for skews over 20 degrees. Diaphragms shall be cast integral with girder webs. 402.07

DEFLECTIONS (AASHTO 9.11)

The deflection shall be calculated using dead load including barriers, but not the future wearing surface, gross section properties and calculated final losses. The additional long term deflection shall be calculated by multiplying the deflection by two. An additional parabolic shaped deflection with a peak equal to 30 millimeters per 100 meters should be added to the total deflection for simple spans. The final long term deflection shall be the sum of the deflection, the additional long term deflection and the additional deflection for simple spans. The camber shown on the plans shall be the final long term deflection. 402.08

ALLOWABLE STRESSES PRESTRESSING STEEL (AASHTO 9.15.1)

In calculating the stress in the prestressing steel after seating, the friction and anchor set losses only should be included. For post-tensioned members, overstressing for short periods of time to offset seating and friction losses is permitted but the maximum allowable jacking stress for low relaxation strand shall be limited to 0.78 f ′s. 402.09

Minimum top slab thickness shall be 200 millimeters. Minimum bottom slab thickness shall be 150 millimeters. Minimum web thickness shall be 300 millimeters (measured

DIAPHRAGMS (AASHTO 9.10)

ALLOWABLE STRESSESCONCRETE (AASHTO 9.15.2)

In calculating the temporary stress in the concrete before losses due to creep and shrinkage, the friction, anchor set and elastic shortening losses should be included.

Part 3 400-2

ROADWAY DESIGN MANUAL – Roads and Bridges Special consideration shall be given to bridges supported on falsework with large openings where deflections could be harmful to the structure. Unless falsework requirements are strengthened or other means taken to ensure the bridge does not form tension cracks prior to tensioning, the maximum allowable tension in a precompressed tensile zone shall be limited to zero. 402.10

LOSS OF PRESTRESS (AASHTO 9.16)

For multi-span bridges, the cable path should have its low point at the midspan. Design should be based on usage of galvanized rigid ducts with K = 0.00000066 and µ = 0.25. Anchor set losses should be based on 16 millimeter set. For creep of concrete, the variable fcds should be calculated using the total dead load applied after prestressing, including the 120 kg/m2 future wearing surface. 402.11

FLEXURAL STRENGTH (AASHTO 9.17)

In determining the negative ultimate moment capacity, the top layer of temperature and shrinkage and bottom layer of distribution reinforcing may be used. In determining the positive ultimate moment capacity, the longitudinal flange reinforcing (AASHTO 9.24) may be used. 402.12

SHEAR (AASHTO 9.20)

Girder webs will be designed for shear using the Ultimate Strength Method according to the 1979 Interim AASHTO Standard Specifications. The maximum girder web stirrup spacing will be 300 mm within 6 meters from the front face of the abutment diaphragms. This will eliminate the need for re-spacing the web stirrups at the point of web flare if the post-tensioning system requires flaring. The value of "d" to be used in shear calculations shall be the larger of the calculated "d" value or 0.8 times the overall effective depth. Horizontal shear shall be investigated in accordance with the provisions of AASHTO 9.20.4.

Calculations shall include the shear due to secondary moment and cable shear. For curved box girder bridges, the shear due to torsion shall be included. 402.13

FLANGE REINFORCEMENT (AASHTO 9.24)

Reinforcing in the bottom slab of box girders shall conform to the provisions of AASHTO 8.17.2.3 except that the minimum distributed reinforcing in the bottom flanges parallel to the girders as specified in AASHTO 8.17.2.3.1 shall be modified to be 0.30 percent of the flange area. 402.14

METHOD OF ANALYSIS

The superstructure may be designed using the system as described below: 1) The bottom slab, in the vicinity of the intermediate support, may be flared to increase its thickness at the face of the support when the required concrete strength exceeds 320 kg/cm2. When thickened, the bottom slab thickness should be increased by a minimum of 50 percent. The length of the flare should be at least one-tenth of the span length (measured from the center of the support) unless design computations indicate that a longer flare is required. 2) Section properties at the face of the support should be used throughout the support; i.e. the solid cap properties should not be included in the model. 3) Negative moments should be reduced to reflect the effect of the width of the integral support. 4) Dead load forces should not produce any tension in the extreme fibers of the superstructure. 5) The superstructure should be designed as a unit with the number of live loads applied in accordance with Section 202.02 of this manual. For box girders with severe sloping webs or boxes over 2 meter deep, transverse flange forces induced by laterally inclined longitudinal post-tensioning shall be considered in the design.

Part 3 400-3

ROADWAY DESIGN MANUAL – Roads and Bridges Single span structures should be jacked from one end only. Symmetrical two span structures may be jacked from one end only or jacked from both ends. Unsymmetrical bridges should be jacked from one end or both ends as required by the design. Three span or longer structures should be jacked from both ends. Several prestressing systems should be checked to verify that the eccentricity and anchorage details will work. In determining the center of gravity of the strands, the Z factor, the difference between the center of gravity of the strands and the center of the ducts, shall be considered. For structures over 120 meters in length, in determining the c.g. of the strands, the diameter of the ducts should be oversized by 13 millimeters to allow for ease of pulling the strands. For horizontally curved bridges, special care shall be taken in detailing stirrups and duct ties. Friction losses should be based on both vertical and horizontal curvatures. In designing for horizontal curvature, the exterior web with the smallest radius shall be used. Consideration to the ± 5% variation allowed per web shall be included.

403 PRECAST PRESTRESSED CONCRETE 403.01

CONCRETE (AASHTO 9.2)

Concrete for highway structures shall have a minimum specified initial and final concrete strengths as shown below. Higher strength concrete may only be used when required by design and when approved. Initial

f ′ci = 290 kg/cm2 Min f ′ci = 320 kg/cm2 Max

Final

f ′c = 360 kg/cm2 Min f ′c = 420 kg/cm2 Max

403.02

The Release Deflection equals the deflection the prestress girder undergoes at the time of strand release. The Release Deflection includes the dead load of the girder and the release prestressing force (including the effects of elastic shortening). The Initial Deflection equals the deflection the prestress girder undergoes at the time of erection prior to the diaphragm or deck pours. The Initial Deflection includes the deflection due to the dead load of the girder, the initial prestressing and the effects of creep and shrinkage up to the time of erection. The time of erection should be assumed to be 60 days after release. The Final Deflection equals the deflection due to the dead load of the deck slab, diaphragms and barriers and the effects of long term creep on the composite girders. The effects of the 120 kg/m2 future wearing surface shall be excluded from deflection calculations. Minimum build-up at the edge of Type III girders and smaller shall be 15 millimeters. For Type IV, V and VI girders the minimum build-up shall be 25 millimeters. This minimum build-up at the critical section will ensure that the flange of the girder will not encroach into the gross depth of the slab. The tops of the erected girders shall be surveyed in the field prior to placement of the deck forming. If the tops of the erected girder elevations are higher than the finish grade plus camber elevations minus deck slab and buildup thickness, adjustments will have to be made in the roadway profile or in the girder seat elevations. Encroachment into the slab of up to 15 millimeters will be allowed for random occurrences. 403.03

DEFLECTIONS (AASHTO 9.11)

The Release, Initial and Final Deflections shall be shown on the plans. Deflections shall be shown in centimeters at the tenth points.

ALLOWABLE STRESSESPRESTRESSING STEEL (AASHTO 9.15.1)

For pretensioned members, overstressing the prestressing steel above the initial stressing limit for short periods of time to offset seating losses is not permitted.

Part 3 400-4


ALLOWABLE STRESSESCONCRETE (AASHTO 9.15.2)

In calculating the temporary stress in concrete before losses due to creep and shrinkage, the steel relaxation prior to release and the elastic shortening should be included.

The location of the harped point of the strand should be located as required by design with the preferable locations being near the 1/10 of the span as measured from the midspan of the girder.

404 PRESTRESSED I-GIRDERS 404.01

403.05

LOSS OF PRESTRESS (AASHTO 9.16)

For creep of concrete, the variable fcds, should be calculated using the total dead load applied after prestressing including the 120 kg/m2 future wearing surface. For girders with required concrete release strengths of 320 kg/cm2 or less, the time of release may be assumed to be 18 hours. For specified strengths over 320 kg/cm2 the time of release should be increased accordingly. For precast girders, the final losses shall include release losses. The value of relative humidity to be used in calculating shrinkage losses, shall be the value of relative humidity at the bridge site. 403.06

SHEAR (AASHTO 9.20)

The value of "d" to be used in shear calculations shall equal the depth of the beam plus the effective depth of the slab with a minimum d = 0.80 times the overall depth. The shear shall be calculated assuming full continuity for composite dead load and live load plus impact. For single span structures, use the shear design spacing at the 1/4 point for sections from the end of the beam to the 1/4 point. For continuous multi-span structures, use the shear design spacing required from the 1/4 point to the pier for the section from the 1/4 point to the abutment end to obtain a symmetrical reinforcing pattern for all girders. 403.07

METHOD OF ANALYSIS

The dead load shall be assumed to be unsupported and carried by the girders only. Use of masked strands for debonding shall not be allowed.

GENERAL

Precast Prestressed I-Girder Bridges shall be designed in accordance with AASHTO specifications. Girders shall be designed by Working Stress Method and checked by the Ultimate Strength Method (Load Factor Design). The deck slab is to be designed by the Working Stress Method using a maximum allowable stress of Fc = 110 kg/cm², Class K 335. The slab and diaphragm dead load is to be supported by the girders only. The Girders are to be designed as a compositesection, simply-supported beams for Live Load and Impact and all superimposed dead loads. Negative moment reinforcement is to be designed over the intermediate supports considering span continuity and all loads. Continuity designs will include shrinkage and creep moments as required by AASHTO Article 9.7.2.1. 404.02

CONCRETE

The following concrete strengths are the desired strengths to be used. Higher strengths may be used if approved by the Abu Dhabi Roads Section Project Manager. Initial

f ′ci = 280 kg/cm² minimum. f ′ci = 350 kg/cm² maximum.

Note: 350 kg/cm² release strengths can be usually obtained within 18 hours, but require 4 to 6 additional hours for each additional 7 kg/cm² required above 350 kg/cm². Permission is required from the Abu Dhabi Roads Section Project Manager for release strengths above 350 kg/cm² and final strengths above 420 kg/cm². Final

Part 3 400-5

f ′c = 350 kg/cm² minimum f ′c = 420 kg/cm² maximum


The maximum allowable stresses are to be in accordance with AASHTO except as modified below:

Allow an extra 40 mm movement per 100 meters of girder length for long-term creep and shortening due to prestressing.

Tension Load Condition Stress Girder DL + Prestress Total Service Load

Elastomeric bearing pads will be a maximum width of 50 mm less than the normal width of the bottom flange to accommodate the 20 mm side chamfer and should be set back 50 mm from the end of the girder to avoid spalling of the girder ends.

404.03

Allowable 0 0.8 ƒ 'c

404.07

EFFECTIVE FLANGE WIDTH (AASHTO 9.8 AND 8.10.1)

The effective flange width will be as specified by AASHTO except for Type V and standard and modified type VI girders where the requirement of 12 times the slab thickness plus web thickness will be increased by 430 mm. 404.04

SHEAR

Girders will be designed for shear using the latest AASHTO Standard Specifications. The depth to be used in the calculation of shear will be the depth of the beam plus the depth of the of the slab. If composite action is fully developed, the shear will be calculated assuming full continuity for composite dead load and live load plus impact. 404.05

INTERMEDIATE DIAPHRAGMS (AASHTO 9.10)

A single 300 millimeter thick intermediate diaphragm shall be placed at the midspan for all spans over 12 meters. For skews less than or equal to 10°, place the diaphragms parallel to the skew. For skews greater than 10º, the diaphragms shall be staggered and placed normal to the girders. 404.06

CREEP FACTOR

Use a creep factor of 3 when calculating long term deflections. 404.08

FRAMES AND CONTINUOUS CONSTRUCTION (AASHTO 9.7.2)

Girders shall be designed as composite section, simple supported beams for live load plus impact and composite dead load. The superstructure shall be constructed continuous with the negative moment reinforcing designed considering continuity over intermediate supports for live load plus impact and composite dead loads. The positive moment connection may be designed using the method described in the PCA publication "Design of Continuous Highway Bridges with Precast, Prestressed Concrete Girders". In determining the positive restraint moment, use 30 days as the length, of time between casting the girders and deck closure. The development length of the strands may be based on the criteria contained in Report No. FHWARD-77-14, "End Connections of Pretensioned IBeam Bridges" November 1974. In determining the number and pattern of strands extended, preference shall be given to limiting the number of strands by increasing the extension length and alternating the pattern to increase constructability.

BEARING PADS

Laminated neoprene bearing pads should be used for relatively light reactions and moderate superstructure movements. Pot type bearings should be used for heavy reactions, large superstructure movements and superstructure on horizontal curve alignment. Part 3 400-6


DIFFERENTIAL SHRINKAGE (AASHTO 9.13.3.3)

406 406.01

Differential shrinkage should be considered in the design when the effects become significant and when approved by the Project Manager. 404.10

METHOD OF ANALYSIS

AASHTO Type V and Type VI modified girders should be used in place of Type V and Type VI regular girders whenever possible. The theoretical build-up depth shall be ignored for calculation of composite section properties.

405 PRESTRESSSED VOIDED SLABS 405.01

406.02

DIAPHRAGMS

Diaphragms shall be cast within the slab at midspan for spans up to 12 meters and at third points for spans over 12 meters.

Diaphragms, cast within the beam, shall be provided at the midspan for spans up to 15 meters, at the third points for spans from 15 to 22 meters and at quarter points for spans over 22 meters.

SHEAR KEYS

LATERAL TIES

One lateral tie shall be provided through each diaphragm located at the mid-depth of the section.

After shear keys have been filled with an approved non-shrink, low slump mortar, lateral ties shall be placed and tightened.

SHEAR KEYS

After shear keys have been filled with an approved non-shrink mortar, lateral ties shall be placed and tightened. 405.05

LATERAL TIES

One lateral tie shall be provided through each diaphragm located at the mid-depth of the section. However, for the 990 millimeter and 1065 millimeter deep sections, when adjacent units are tied in pairs for skewed bridges, in lieu of continuous ties, two ties shall be provided, located at the third points of the section depth. 406.04

405.04

DIAPHRAGM

END BLOCKS

End Blocks should be 380 millimeters long with sufficient steel provided to resist the tensile forces due to concentrated prestressing loads.

405.03

END BLOCKS

END BLOCKS 450 MILLIMETERS LONG SHALL BE PROVIDED AT EACH END AND SUFFICIENT STEEL SHALL BE PROVIDED IN THE END BLOCKS TO RESIST THE TENSILE FORCES DUE TO THE PRESTRESSING LOADS.

406.03

405.02

PRESTRESSED BOX BEAMS

BARRIERS

Barriers shall have a 6 millimeter open joint at the midspan to prevent the barrier from acting as an edge beam and causing long term differential deflection of the exterior beam.

Part 3 400-7


SECTION 500 STRUCTURAL STEEL 501 501.01

501.05

The stress cycle case to be used in AASHTO Table 10.3.2A shall be Case I.

DESIGN CRITERIA

501.06

GENERAL

Structural steel design criteria shall be as specified in Section 10 of AASHTO except as clarified or modified in this manual. 501.02

DESIGN METHODS

The Service Load Design Method (Allowable Stress Design) shall be used except that the Strength Design Method (Load Factor Design) may be used for major or unusual structures when approved. 501.03

MATERIALS (AASHTO 10.2)

Materials shall conform with the requirements of AASHTO Article 10.2 with the selection based on stress requirements and overall economy. The preferred maximum thickness of tension flanges is 50 millimeters. Tension flanges thicker than 50 millimeters shall be normalized. 501.04

LOAD CYCLES (AASHTO 10.3.2)

CHARPY V-NOTCH IMPACT REQUIREMENTS (AASHTO 10.3.3)

Where applicable, the Charpy V-Notch impact requirements for structural steel shall be for Temperature Zone 1 at elevations less than 1800 meters and Temperature Zone 2 at elevations 1800 meters and higher, unless otherwise directed by the Project Manager. Intermediate stiffeners shall be placed only on the inside face of exterior girders. The number and location of girder shop and field splices shall be determined so as to minimize fabricated and erected cost of the girders. All connections except field connections shall be welded. ASTM A325M high strength bolts shall be used for field connections.

ALLOWABLE FATIGUE STRESS (AASHTO 10.3.1)

Splices, stiffeners, shear connectors and bracing details shall be designed using categories A through C details in order to limit the fatigue stress. Category E details shall not be used.

Part 3 500-1


SECTION 600 EXPANSION AND CONTRACTION 601

To allow for the effects of long term creep and shrinkage in post-tensioned box girder bridges, the following additional shortening shall be included:

MOVEMENT CRITERIA

601.01

Joints: Bearings:

MOVEMENT RATING

Provisions shall be made in the design of structures to resist induced stresses or to provide for movements resulting from variations in temperature and anticipated shortening due to creep, shrinkage or prestressing. Accommodation of thermal and shortening movements will entail consideration of deck expansion joints, bearing systems, restraining devices and the interaction of these three items. The main purpose of the deck joint is to seal the joint opening to obtain a watertight joint while allowing for vertical, horizontal and/or rotational movement. The bearings are required to transmit the vertical and lateral loads from the superstructure to the substructure units and to allow for movement in the unrestrained directions. Restraining devices are required to limit the displacement in the restrained directions. Improper design or construction of any of these devices could adversely affect the operation of the other devices. The required movement rating is equal to the total anticipated movement (i.e. the difference between the widest and the narrowest opening of a joint). The calculated movements used in determining the required movement rating shall be as specified in AASHTO except as modified below:

602 602.01

40 mm per 100 meters. 80 mm per 100 meters.

DECK JOINTS GENERAL

The movement rating for joints for steel structures shall be based primarily on the thermal expansion and contraction characteristics of the superstructure, while for concrete structures the effects of shortening due to creep and shrinkage and where applicable, prestressing shall also be added. Movement ratings shall be based on temperature variations as measured from the assumed mean temperature. Published movement ratings are usually based on the difference between the maximum and minimum openings without consideration to the required minimum installation width. In determining the movement rating, consideration must be given to the installation width required to install the seal element. Other factors which should be considered in determining the required movement rating include consideration of the effects of any skew, anticipated settlement and rotations due to live loads and dead loads, where appropriate. Items requiring attention include:

Mean temperature and temperature ranges shall be as specified in Section 201.08 of this manual. To allow for the effects of long term creep and shrinkage in precast prestressed concrete members, the following additional shortening shall be considered:

1) 2) 3) 4) 5) 6) 7)

Joints: 20 mm per 100 meters. Bearings: 40 mm per 100 meters.

8)

Part 3 600-1

The type of anchorage system to be used. The method of joint termination at the ends. The method of running joints through barriers, sidewalks and/or medians. Physical limitation on size of joints. Susceptibility of joint to leakage. Possible interference with post-tensioning anchorages. Selection of appropriate modular proprietary systems that meet design requirements. Forces applied to the surrounding concrete by the joint.

ROADWAY DESIGN MANUAL – Roads and Bridges Available types of joints include compression seals, strip seals, and modular joints. Compression seal joints and strip seal joints are generic and should be detailed on the plans, by standards and/or covered in the special provisions. Modular joints are proprietary and require that the designer specify allowable joint types and styles in the special provisions. Information concerning specific design parameters and installation details of modular joints should be obtained from literature supplied by the manufacturer of the system. It is the responsibility of the designer to review the proprietary joint literature and related manufacturer's specifications to ensure that the selected joint types are properly specified and compatible with the design requirements. The following features of joints should be shown on the plans: 1)

2)

3) 4) 5)

6)

Blockout details showing a second pour, including blockout dimensions and additional reinforcing required. Required end treatment in barriers or curbs, including enough detail or explanation to accommodate each of the proprietary systems selected (i.e. cover plates, etc.). Consideration to traffic control in determining section pattern lengths. Movement rating. Assumed temperature and opening at time of installation with temperature correction factors. Actual horizontal length of joint measured from inside of barrier face to inside of barrier face corrected for skew.

list of approved joint types which can be obtained from the Project Manager. 602.02

COMPRESSION SEALS

The compression seal element should have a shape factor of 1:1 (width to height) to minimize side wall pressure. The size of the compression seal shall be specified on the plans. Effective movement ratings for this type of joint range up to 50 millimeters. Advantages for this type of joint include its low cost, proven performance and acceptance for use on pedestrian walkways. However, this type of joint can not be unbolted and easily raised, generates pressure and is not good for high skews or horizontal directional changes. 602.03

STRIP SEALS

Strip seals should generally conform to the details shown in the structure detail drawing titled "Strip Seal Joint". Proprietary alternates to this detail other than those shown on the detail drawing will not be allowed. Effective movement ratings for this type of joint range up to 100 millimeters. This type of joint is best used when the movement rating is beyond the capacity of compression seals and for large skews. Strip seal joints will require cover plates for pedestrian walkways. 602.04

MODULAR JOINTS

The following features of joints should be specified in the specifications:

Modular joints are very complex joint systems. Effective movement ratings range from 100 millimeters up to 750 millimeters. Modular joints are the best choice for movement ratings over 100 millimeters.

1)

603

2)

For modular joints, the joint style, gland type, steel edge beam material, and the name of a representative manufacturer. Method of measurement (by linear meter from face to face of barrier).

A general discussion of joint types follows. However, for modular joints the actual selection of the specific alternates should be made from the

603.01

BEARINGS GENERAL

Unlike joints, where the opening can be adjusted if the ambient temperature at the time of construction is different than the assumed mean temperature, bearings must be designed to be installed at temperatures other than the mean temperature. For this reason, the movement

Part 3 600-2

ROADWAY DESIGN MANUAL – Roads and Bridges rating should be based on the full temperature range and not the rise or fall from a mean temperature.

due to prestressing is greater than 25 millimeters and where the movement rating including elastic shortening, long term creep and shrinkage and temperature is greater than 40 millimeters.

Calculation of the movement rating shall include thermal movement and anticipated shortening due to creep, shrinkage and prestressed shortening. For cast-in-place post-tensioned concrete box girder bridges both the elastic and long term prestress shortening effects shall be considered.

603.03

An initial offset of the top sliding surface from the centerline of bearing should be calculated and shown on the plans so that the top sliding surface will be centered over the bottom sliding surface and the centerline of bearing after all shrinkage, creep and post-tensioning shortening has taken place in the sperstructure. Permissible bearing types include neoprene strips, elastomeric bearing pads, steel bearings, sliding elastomeric bearings and high-load multirotational bearings (pot, disc or spherical). Neoprene strips, elastomeric bearing pads and steel bearings are generic and shall be detailed on the plans and/or covered in the standard specifications and special provisions. High-load multi-rotational bearings are proprietary bearing types and require that the designer include a Bearing Schedule in the plans. It is the responsibility of the designer to review the Stored Specification to ensure that the bearings are properly specified and compatible with the design requirements. Sliding elastomeric bearings are both generic and proprietary in that a generic bearing should be designed and detailed on the plans with proprietary alternates allowed. All bearings types except elastomeric bearing pads shall be designed for impact. 603.02

NEOPRENE STRIPS

Neoprene strips consist of a sliding plate on a continuous neoprene pad. Where appropriate, neoprene strips are the preferred bearing type for post-tensioned box girder bridges. However, neoprene strips are not appropriate for the following applications: curved bridges, skews greater than 20 degrees, contributing spans greater than 50 meters, where initial shortening

ELASTOMERIC BEARING PADS

Elastomeric bearing pads shall conform to the requirements of Section 14 of AASHTO. Bearing pads shall be designed to be constructed using either steel or fiberglass laminates, with the controlling case determining the size. The following data should be shown on the plans: Length, width and thickness of pad Durometer Hardness Design Method (A or B) Design Load Low Temperature Zone (A, B or C) Elastomer Grade (0, 2 or 3) Shear Modulus Generally, bearing pads shall be Durometer 60 Elastormer with steel reinforcement. Normally Design Method A will be used in design, however, where only steel reinforced pads will work Design Method B may be used provided the special testing is performed. The following should be used as a guide for determining low temperature zones: Elevation (meters) Below 900 900-1800 1800 and above

Zone A B C

Pads shall have a minimum thickness of 25 millimeters and be designated in 10 millimeter increments. The use of elastomeric bearing pads should generally be limited to a thickness not greater than 100 millimeters. Holes will not be allowed in the pads. Width and length dimensions shall be detailed in even 50 millimeter increments. When used with prestressed I-girders, pads shall be sized a minimum width of 50 millimeters less than the nominal width of the girder base to accommodate the 20 millimeter side chamfer and shall be set

Part 3 600-3

ROADWAY DESIGN MANUAL – Roads and Bridges back 50 millimeters from the end of the girder to avoid spalling of the girder ends. Elastomeric pads should not be used in cases where deck joints or bearings limit vertical movements, such as in older style sliding steel plate joints or widenings where existing steel bearings are to remain. Where elastomeric bearing pads with greased sliding plates are used on post-tensioned box girder bridges to limit the required thickness of the pad, the pad thickness should be determined based on temperature movements only, with the initial and long term shortening assumed to be taken by the sliding surface. Elastomeric bearing pads are the preferred bearing type for new steel girders, precast prestressed girders and post-tensioned box girder bridges where neoprene strips are not appropriate. 603.04

STEEL BEARINGS

Steel bearings may consist of rockers or fixed or expansion assemblies which conform to the requirements specified in Section 10 of AASHTO. Steel bearings are not a preferred bearing type and their use should normally be limited to situations where new bearings are to match the existing bearing type on bridge widening projects. 603.05

SLIDING ELASTOMERIC BEARINGS

Sliding elastomeric bearings consist of an upper steel bearing plate anchored to the superstructure, a stainless steel undersurface and an elastomeric pad with a teflon coated upper surface. The teflon surface shall be attached to a 10 millimeter minimum thick plate which is vulcanized to the elastomeric pad. The bearing accommodates horizontal movement through the teflon sliding surface and rotation through the elastomeric bearing with the thickness of the elastomeric bearing determined by the rotational and friction force requirements. Keepers may be used for horizontal restraint of the pads. Vertical restraint may be provided by anchor bolts with slotted keeper plates or individual vertical restrainers as

appropriate. The pad dimensions and all details of the anchorage and restraint systems shall be shown on the plans. The special provisions should allow for proprietary alternates. Sliding elastomeric bearings should be considered for applications where regular elastomeric bearing pads would exceed 100 millimeters in height or where special access details would be required for other proprietary bearings in such places as hinges. 603.06

603.06.01

HIGH-LOAD MULTIROTATIONAL BEARINGS Description

High-load multi-rotational fixed bearings consist of a rotational element of the Pot-type, Disc-type or Spherical-type. High-load multi-rotational expansion bearings consist of a rotational element of the Pot-type, Disc-type or Spherical-type, sliding surfaces to accommodate translation and guide bars to limit movement in specified directions when required. Pot bearings consist of a rotational element comprised of an elastomeric disc totally confined within a steel cylinder. Disc bearings consist of a rotational element comprised of a polyether urethane disc confined by upper and lower steel bearing plates and restricted from horizontal movement by limiting rings and a shear restriction mechanism. Spherical bearings consist of a rotational element comprised of a spherical bottom convex plate and mating spherical top concave plate. These design criteria were prepared for the broad range of normal applications and the specified limits of loads, forces and movements. The design and manufacture of multi-rotational bearings relies heavily on the principles of engineering mechanics and extensive practical experience in bearing design and manufacture. Therefore, in special cases where structural requirements fall outside the normal limits, a bearing manufacturer should be consulted.

Part 3 600-4


9.

Rotational Requirements

The rotational requirements of these bearings is treated in a new way. Rotational requirements of the bearings, Rb, are determined by: Rb =

10. Large movements are anticipated. 11. Economical, long life, or low maintenance bearings are desirable.

Rs + Rc

where Rb = Rs =

Rc =

603.06.03

Rotation capacity designed into the bearing. Anticipated rotation of the structure in service. (includes live loads and rotations induced by construction/erection sequences). Rotation induced in the bearing by construction tolerances, 0.02 radians maximum (see Design Criteria 14). Use

Use of multi-rotational bearings is especially indicated where: 1.

Low profile, high load bearings are required.

2.

Long span, curved, or skewed bridges and other similar structures of complex design are required.

3.

Long slender columns or light frames and members exhibit minimum stiffness or rigidity.

4.

The direction of rotation varies.

5.

The direction of rotation cannot be precisely determined.

6.

It is desirable to reduce the moment applied to truss or space frame panels.

12. Regular elastomeric bearing pads would exceed 100 millimeters in height. 603.06.04

Since special details are required to allow for access for inspection, repair or replacement of the bearings, the respacing of joints to eliminate the need for use of these bearing types should be considered. Some structural considerations in use of multirotational bearings are listed below. Reference to "this specification" refers to the design criteria below. 1.

Vertical and horizontal loads shall be assumed to occur simultaneously. All loads are service loads. Minimum vertical loads are for dead loads and superimposed dead loads excluding the future wearing surface. Maximum vertical loads are for dead loads, superimposed dead loads including the future wearing surface, and live loads and impact.

2.

The total recommended clearance between all guiding and guided sliding surfaces is 1.5 millimeters in order to limit edge stress on guiding interfaces.

3.

Avoid specifying total spacing of more than 1.5 millimeters between guides and guided components where possible.

4.

In specifying the horizontal force capacity of bearings, it is recommended only one fixed or guided expansion bearing shall be assumed to resist the sum of all the horizontal forces at each abutment, bent, column, hinge or pier.

Settlement of the substructure is anticipated.

7.

Self aligning capabilities are required.

8.

Load and rotation eccentricity does not significantly alter the net distribution of stress through the bearing and into the substructure and superstructure.

Design Criteria

Part 3 600-5

ROADWAY DESIGN MANUAL – Roads and Bridges 5.

6.

7.

8.

9.

Where feasible provide at least two fixed or guided expansion bearings each able to resist all horizontal forces at each abutment, column, hinge or pier for design redundancy. Some press-fit guide bar details in common use have proven unsatisfactory in resisting horizontal loads. When analyzing these designs, consideration should be given to the possibility of rolling of the bar in the recess. Multi-rotational bearings should not be used at vertical loads less than 20% of their vertical capacity. Bearings for less than 20% vertical capacity require special design. Special consideration in bearing design shall be given where high horizontal to vertical load (above 0.30) is anticipated. Frictional resistance of bearing slide surfaces should be neglected when calculating horizontal load capacity.

10. The installed alignment of bearing guiding systems relative to the anticipated movement direction of the structure should be carefully considered to avoid bearing guide system failure. Special studies or designs may be required on curved or skewed structures to ensure correct installation. 11. The substructure and superstructure should be designed so as to remain rigid under all service conditions in areas around and in contact with the bearings, paying particular attention to the use of stiffeners at extreme points of movements. 12. The substructure and superstructure design should permit bearings to be removed for inspection or rehabilitation by minimum jacking of the structure. Jacking points shall be provided in the structural design. Part 3 600-6

13. The minimum Structure Rotational, Rs, of bearings covered in the specification is 0.01 radians. Rs comprises live loads and rotations induced by construction/erection sequences. 14. The maximum Construction Rotation, Rc (rotation induced by construction tolerances), is 0.02 radians. The designer may elect to specify a smaller Rc than 0.02 radians but is cautioned to investigate the cost and practicality of the changes contemplated. 15. Recommended coefficients of friction for structure design follows: Unfilled sheet or woven fiber PTFE/stainless steel 0.04 Filled PTFE sheet/stainless 0.08 The above coefficients of friction are based on the average stress and limits of edge stress of PTFE in this specification. Out of level installations within the limits of this specification and normal in service oxidation of the stainless steel mating surface. Service conditions, where exceptional corrosion of the stainless steel mating surface may occur, will require special assessment of the long term coefficient of friction. 16. Pot, disc and spherical multi-rotational bearings should not be mixed at the same expansion joint or bent. The differing deflection characteristics and differing rotation characteristics may result in damage to the bearings and/or structure. 17. Contract drawings and documents should contain a Bearing Schedule (See Section 603.07, Bearing Schedule). 18. Some bearing tests are very costly to perform. Other bearing tests cannot be performed because of the unavailability of test equipment. The following test

ROADWAY DESIGN MANUAL – Roads and Bridges requirements should be carefully considered before specifying them:

9. Allowable coefficient of friction of slide surfaces.

A) Vertical loads exceeding 2,250,000 kg.

10. Surface coating requirements and the appropriate specifications.

B) Horizontal loads exceeding 225,000 kg.

11. Seismic requirements, if any. 12. Uplift details, temporary attachments or other requirements.

C) The simultaneous application of horizontal and vertical loads where the horizontal loads exceeds 75% of the vertical loads. D) Triaxial test loading. E) The requirement for dynamic rotation of the test bearing while under vertical load.

13. Installation scheme. 14. Bearing preset details, if required. Design rotation, movement and other requirements in the Bearing Schedule should only refer to the requirements of the structure where the bearings are to be used.

604 603.07

RESTRAINING DEVICES

BEARING SCHEDULE 604.01

A bearing schedule shall be included in the contract drawings and documents and shall contain the following as a minimum: 1. A schedule of all minimum and maximum vertical and horizontal service loads. 2. Minimum Structure and Construction Rotation requirements. 3. Magnitude and direction of movements at all bearing support points. 4. Quantity, type (fixed, expansion or guided expansion). 5. Plan view, alignment and location of all bearing units. 6. Allowable upper and lower bearing contact pressure.

GENERAL

Restraining devices are meant to prohibit movement in a specified direction. Restraining devices shall be designed to resist the imposed loads including earthquake as specified in AASHTO and as modified in Section 200 of this manual. Restraining devices could include concrete shear keys or end blocks, horizontal or vertical cable restrainers or mechanical restraining devices which could be an integral part of a bearing or a separate system. Restraining devices to prohibit vertical displacement at expansion ends, shall be designed to allow for inspection and future replacement of bearings. Allowable restraining devices include, but are not limited to the following: Vertical Fixed Restrainers, Vertical Expansion Restrainers, External Shear Keys, Internal Shear Keys and Keyed Hinges.

7. Fixing or anchorage details and/or requirements.

604.02

8. Grades, bevels and slopes of all bearings.

Vertical fixed restrainers consist of cable and appropriate hardware and are designed to allow

Part 3 600-7

VERTICAL FIXED RESTRAINERS

ROADWAY DESIGN MANUAL – Roads and Bridges rotation but no translation in either horizontal or vertical directions. 604.03

EXTERNAL SHEAR KEYS

External shear keys are reinforced concrete blocks designed to limit transverse displacement while allowing longitudinal and rotational movements. External shear keys are preferred to internal shear keys since they are more accessible for repairs and easier to construct. 604.05

KEYED HINGE

A keyed hinge is a restraining device which limits displacements in both horizontal directions while allowing rotation.

VERTICAL EXPANSION RESTRAINERS

Vertical expansion restrainers consist of cable and appropriate hardware and are designed to allow rotation and longitudinal translation but no transverse translation. Some limited vertical displacement is allowed to permit replacement of bearings if required. 604.04

604.06

For a typical expansion seat abutment where restraining devices are required, the restraining devices will consist of vertical expansion restrainers and external shear keys. For a typical pinned seat abutment for a posttensioned box girder bridge, restraining devices will consist of vertical fixed restrainers and external shear keys. For a typical pinned seat abutment for a prestressed girder bridge, restraining devices will consist of vertical fixed restrainers and external or internal shear keys. For a typical expansion pier, restraining devices will consist of vertical expansion restrainers and internal shear keys.

INTERNAL SHEAR KEYS

Internal shear keys are reinforced concrete blocks designed to limit transverse displacement while allowing longitudinal and rotational movements.

For a typical pinned pier, restraining devices will consist of vertical fixed restrainers and internal shear keys or a keyed hinge.

Part 3 600-8


SECTION 700 GEOTECHNICAL 701 701.01

701.02

FOUNDATIONS GENERAL

The main purpose of this section is to document bridge design criteria as related to bridge foundation geotechnical issues. Since problems requiring geotechnical and structural expertise often result in confusion concerning the responsibilities of each, another purpose of this section is to define the role of the geotechnical engineer and the bridge engineer in design problems involving both fields. The usual procedure for designing bridge foundation substructure units is as follows: The bridge design group preliminary location plan.

will develop

a

The Geotechnical Engineer will conduct a site investigation, identify borehole locations, drill and log borings, perform soil testing as appropriate, plot the boring logs and summarize the results in a Geotechnical Report. The Geotechnical Report will include a Foundation Design Report which identifies the type of foundation recommended for each substructure unit including the allowable loads and required depths. The Geotechnical Engineer is responsible for preparing the boring logs on construction plans. They also prepare necessary special provisions for construction of the foundation elements. During construction of the bridge foundations, the Geotechnical Engineer oversees geotechnical testing, spread footing excavations and piling and drilled shaft construction. They work closely with bridge design group to jointly resolve problems requiring redesign because of changed site conditions. The bridge design group is responsible for producing the structural design and construction documents for the substructure units as part of the bridge plans.

SPREAD FOOTINGS

Where good soil materials exist near the surface, shallow foundations in the form of spread footings will normally be the recommended foundation type. For foundation units situated in a stream, spread footings shall only be used when they can be placed on non-erodible rock. Spread footings are normally not placed on embankment material. When spread footings are the recommended foundation type, the Geotechnical Report shall contain the allowable bearing pressure, the elevation of the bottom of the footing and the estimated total settlement, differential settlement and time rate of settlement, if applicable. The bridge design group shall size the footing to ensure that the allowable bearing pressure is not exceeded for any AASHTO Group Loading and that the footing is properly sized and reinforced to resist the maximum applied moments and shears. The bottom elevations of spread footings shall be set at the recommended depth. The minimum top cover over the top of footings shall be 500 millimeters. If the possibility for differential settlement is identified, the bridge designer shall ensure that the entire structure is capable of structurally resisting the forces induced by the differential settlement. 701.03

PILE FOUNDATIONS

When good foundation material is not located near the surface, when settlement is a problem, or for foundation units located in streams where scour is a problem, deep foundations will usually be recommended. One type of deep foundation is a driven pile. Driven piles may be either steel H piles, steel pipe piles or prestressed concrete piles. The other type of deep foundation is a bored pile.

Part 3 700-1


DRIVEN PILES

The Geotechnical Engineer is responsible for recommending when driven piles are to be used, The type of driven pile to be used, the allowable capacity of the pile, the estimated pile tip elevation and any special requirements necessary to drive the piles. When steel piles are used, the corrosive life of the pile will be reported in the Geotechnical Report. The Geotechnical Engineer is also responsible for running the WEAP87 wave equation computer program to determine the driveability of the specified piles and to develop charts or other guidelines to be used by construction personnel to control the pile driving process.

For the most part, bored piles will include a temporary casing or liner intended to preclude the intrusion of earth into the hole during the boring operation and a permanent casing or liner that will remain in place and not be withdrawn during the concreting process. The temporary casing will be advanced a sufficient depth into rock to provide a seal against water inflow. The temporary casing shall be clean and free of water before the permanent casings or liners, reinforcing steel and concrete are placed. The bridge design group is responsible for ensuring that the allowable axial capacity is not exceeded for any AASHTO Group Loading and that the shaft can withstand the applied lateral loads.

The bridge design group is responsible for ensuring that the allowable axial capacity is not exceeded for any AASHTO Group Loading and that the pile can withstand the applied lateral loads.

Unless specified otherwise in the Geotechnical Report, the following minimum criteria should be used in designing bored pile foundations:

701.05

1. Bored Piles shall be spaced a minimum of two diameters measured center to center of the holes plus 100mm.

BORED PILES

A bored pile foundation consists of excavating a round hole by machine, installing a metal casing or liner, placing a reinforcing cage in the casing or liner and then filling the casing or liner with concrete. The Geotechnical Engineer is responsible for recommending the minimum diameter of bored pile to be used and providing the necessary information for determining the minimum required embedment below a specified elevation to develop the required axial load. The Geotechnical Engineer is also responsible for determining the soil properties in each layer to be used in analyzing lateral loads and whether slurry methods of construction may be utilized. If necessary, methods of testing the pile after concreting will be specified in the Geotechnical Report.

2. Temporary and permanent casings or liners shall be designed to withstand handling stresses, applicable concrete and surrounding soil pressures, and shall be watertight. 3. Vertical reinforcing should be detailed to provide the minimum recommended clearance in AASHTO Article 4.6.6.2.1. In no case shall the clearance between vertical reinforcing be less than 115 millimeters. 4. Reinforcement shall have a clear distance of not less than 50 millimeters from the inside face of the permanent casing or lining. 5. Horizontal ties should be spaced at 150 millimeters minimum. 6. The footing, if applicable, shall be sized to extend a minimum of 200 millimeters from the edge of a bored pile.

Part 3 700-2


SECTION 800 RETAINING WALLS 801 801.01

801.02

POLICY

The following policy shall apply to retaining wall design:

DESIGN CRITERIA

1. Walls up to 6 meters high:

GENERAL

The Consultant shall prepare drawings for cast-in-place concrete retaining walls utilizing the Abu Dhabi Roads Section Standards and Specifications.

Retaining walls are used when normal fill or cut slopes extend beyond acceptable limits. Walls may be classified in the following classes: Gravity Walls • Bin • Crib • Wire basket • Mass concrete Cantilever Walls • Concrete Braced Walls • Anchored Walls • Soldier pile and lagging • Tangent cylinder piles Mechanically Stabilized Walls • Reinforced Earth • VSL Retained Earth • Hilfiker-Reinforced Soil embankment Walls shall be designed for a minimum factor of safety of 1.5 against sliding and 2.0 against overturning. The wall selection process includes identification of types of walls appropriate for the site, evaluation of geotechnical behavior and properties affecting wall behavior and selection of wall systems which fit all site constraints. Identification of alternate designs may be appropriate. In determining the types of retaining walls capable of fitting a particular site the following should be considered: • Availability of materials • Service life, maintenance, future use • Deflection tolerance • Ease of construction • Environmental/visual considerations • Special loading requirements • Settlement tolerance • Availability of space

2. Walls over 6 meters high: The Consultant shall evaluate the applicability of mechanically stabilized wall systems and confirm their site-specific suitability. If the Consultant determines that a mechanically stabilized wall system is not appropriate due to soils conditions or other site specific conditions, a complete cast-in-place concrete retaining wall design must be prepared for inclusion into the bid documents. 801.03

RESPONSIBILITIES

The design of a retaining wall will usually involve the efforts of three sections: Roadway Design Section, Geotechnical Section, and the Bridge Design Section. 801.03.01

Roadway Design Section

Roadway Design Section is responsible for identifying the need for and limits of the retaining walls. They will be responsible for providing a profile adjacent to the top of the wall and the soil profile line along the front face of the wall. Roadway Design is also responsible for identifying the acceptable limit of excavation required to maintain traffic and to design any detours when required.

Part 3 800-1


Geotechnical Section

The Geotechnical Section is responsible for investigating the site, drilling exploratory holes as required, determining the external stability of the site and determining the material properties of the existing soil and backfill. The Geotechnical Section will also recommend soil strength parameters and groundwater elevations for computing design lateral earth pressure. They are also responsible for determining the maximum safe slopes allowed during excavation. The Geotechnical Section also is responsible for determining the type of foundation required to support the wall loads, the allowable bearing pressure of the soil and the minimum required depths of the foundation units. This Section determines the soil properties to be used in determining the lateral loads to be applied to the wall and determines the amount of settlement, differential settlement and the time rate of settlement for walls on compressible foundation soils. The Geotechnical Section prepares appropriate Special Provisions for construction of the retaining walls and monitors construction of the foundation elements, assisting the resident engineer as requested concerning geotechnical issues. The Section works closely with the Bridge Design Section on any structural design changes needed during construction because of changed site conditions. 801.03.03

Bridge Design Section

The Bridge Design Section is responsible for the design of the structural elements of the wall, the length of the wall and for producing the required construction plans, when requested by others, for any non-proprietary wall requiring structural analysis. The Bridge Design Section is also responsible for determining whether shoring will be required during construction based on the acceptable limits of excavation provided by Roadway Design and the safe excavation slopes provided by Geotechnical. The Bridge Design Section also selects walls which will handle differential settlement, when present, and provides

details for drainage on plans. Appurtenant traffic and/or pedestrian rails will also be designed and detailed by the Bridge Design Section. This Section works with the Geotechnical Section on required structural design changes during construction because of changed site conditions. 801.04

PROPRIETARY RETAINING WALLS

When a proprietary retaining wall is chosen as an acceptable alternate, the special provisions will specify the pre-approved wall systems which are acceptable for the particular application and site. The proprietary wall type is to be chosen from a pre-approved list of wall types. The contractor will be required to identify the alternate in his bid, with bid shopping after the award of the contract not allowed. The Roadway Design Section will prepare plans showing the location and extent of the walls and the profile along the top of the wall and the soil profile along the front face of the wall. The plans should also show any restrictions regarding excavation which may exist and requirements for appurtenant features such as traffic barrier, handrail or other attachments. Blockouts for lighting, signing, utilities and drainage structures will also be detailed on the plans or identified to be included with the proprietary plan submittals. The Geotechnical Section will prepare special provisions containing the design criteria to be used in evaluating the proprietary wall. As a minimum the following should be included: 1. The minimum factor of safety against overturning 2. The minimum factor of safety against sliding 3. Maximum coefficient of friction against sliding 4. Phi angle of the backfill 5. Allowable bearing pressure 6. Minimum design life 7. Water table level 8. Elevation of footing bottom 9. Maximum tolerable deflection

Part 3 800-2

ROADWAY DESIGN MANUAL – Roads and Bridges structures will not be permitted. Trenching in the vicinity of existing piers or abutments shall be kept a sufficient distance from footings to prevent undercutting of existing footings or to prevent disturbing foundation soils for future foundations.

SECTION 900 MISCELLANEOUS 901

901.01

TRAFFIC STRUCTURAL SUPPORTS GENERAL

Luminaires, traffic signals and sign supports shall be designed using the AASHTO Specifications for Structural Supports except as clarified or modified in this manual. 901.02

WIND SPEED

Major structural supports shall be designed for the wind frequency of 160 kph. 901.03

Where other locations prove to be extremely difficult and very costly, utility lines except natural gas may be allowed in the structures. Natural gas encroachments will be evaluated under the following policy: A. Cases where gas line attachments to structures will not be considered under any condition: 1.

ALLOWABLE STRESSES

2.

The, L /45.7 limitation on dead load deflection contained in Article 1.9.1(A) need not be satisfied since there is no scientific basis to support this limitation. For high mast light poles, the maximum deflection shall be limited to 15% of the pole height under wind load. The maximum allowable yield strength for design purposes shall be 4590 kg/cm2.

3.

4.

B. Gas line attachments on structures will be considered under the following cases or conditions:

For all other applications, for steel with a yield strength greater than 3360 kg/cm2, the allowable stresses for design shall be limited to a yield This limitation strength of 3360 kg/cm2. indirectly places a limit on allowable deflections in an attempt to satisfy the criteria of Article 1.9.1. This limitation also reduces the stresses in any high strength welds which are more brittle and subject to cracking due to fatigue from vibrations.

902 902.01

1. Each case will be judged on its own merit with the utilities providing complete justification as to why alternative locations are not feasible. 2. Economics will not be a significant factor considered in the feasibility issue. 3. Open girder type structures across major rivers. 4. Pedestrian or utility bridges where proper vented casings and other safety systems are used. 5. All lines are protected by casements.

UTILITIES IN STRUCTURES GENERAL

Where utility conflicts exist; water, power, telephone, cable TV and gas lines will be relocated as required for construction of the project. Where it is feasible and reasonable to locate utility lines elsewhere, attachment to

Grade separation structures carrying vehicular traffic on or over freeways. Inside closed cell-type box girder bridges. High pressure transmission lines over 4 kg/cm2 and/or distribution lines of over 150 millimeters in diameter. Gas lines over minor waterway crossings where burial is feasible.

Provision for accommodation of relocated and future utilities on structures should follow the following General Policy.

Part 3 900-1


3. 4. 5. 6.

Size and schedule of sleeved casings. Spacing and details of support brackets. Expansion device details. Total combined weight of carrier pipe and transmitted fluids, conduits, casings, support brackets, expansion joints and other related items. 7. Design calculations.

POLICY

Support bracket details and attachments for all utilities will require Bridge Group approval. All approved utilities shall have individual sleeved casings, conduits or ducts as appropriate. All utilities carrying liquids shall be placed inside casings through the entire length of the structure. The casing shall be designed to carry full service pressure so as to provide a satisfactory containment in case the utility is damaged or leaks.

902.04

The Bridge Group shall be responsible for and have final approval authority for the following aspects of the design:

Water lines, telephone conduits, power lines, cable TV lines, supports or other related items will not be permitted to be suspended below or attached to the exterior of any new or existing structure.

1. Determination of how many lines, if any, the structure can accommodate. 2. Determination of where such lines should be located within a structure. 3. Determination of the size of the access openings and design of the required reinforcing. 4. Determination of construction problems related to required sequencing of project. 5. Tracking man-hours associated with utility relocations for cost recovery.

Product lines for transmitting volatile fluids will not be permitted to be attached to or suspended from or placed within any new or existing structure. 902.03

UTILITY AGENCY RESPONSIBILITY

The utility agency is responsible for obtaining necessary information regarding the proposed construction schedule for the project. The agency shall submit a request including justification for attaching to the structure and preliminary relocation plans including line mass and support spacing as early as possible but no later than the completion of preliminary structural plans. The utility agency shall be responsible for the design of all conduits, pipes, sleeves, casings, expansion devices, supports and other related items including the following information: 1. Number and size of conduits for power, telephone and cable TV lines. 2. Size and schedule of carrier pipe for water lines.

BRIDGE GROUP RESPONSIBILITY

Usually utilities will be accommodated by providing individual access openings for casings and sleeves to pass through. Access openings should be 50 millimeters larger than the diameter of the casings or sleeves and spaced as required by structural considerations. For box girder bridges, access openings should be located as low as possible but no lower than 250 millimeters above the top of the bottom slab to allow for support brackets to be supported from the bottom slab. Where possible all utilities shall be supported from the bottom slab for box girder bridges. For girder bridges, the utilities shall not be placed in the exterior girder bay and shall be supported from the deck slab.

Part 3 900-2

ROADWAY DESIGN MANUAL – Roads and Bridges 903 FALSEWORK POLICY FOR BRIDGE CONSTRUCTION 903.01

903.03

FALSEWORK REQUIREMENTS

To ensure that traffic handling is given proper consideration in the early design stages, it is necessary to identify traffic handling and falsework assumptions in the Bridge Selection Report. If falsework is to be used, the horizontal and vertical clearances shall be shown on the General Plan. Usually, one of the following listed conditions will prevail: 1. Traffic will be routed around construction site. 2. Traffic will pass through construction site. A. No falsework allowed over traffic. This restriction would require precast concrete or steel superstructure with field splices located clear of traffic.

For cast-in-place structures, the preferred method of construction is to route traffic around the construction site and to use earth fills for falsework. This provides an economical solution, a safe working area and eliminates possible problems associated with the design, approval, construction and performance of falsework including the possible effect of excessive deflections of falsework on the structure. When the street or highway must be kept open and detours are not feasible, falsework shall be used with openings through which traffic may pass. Because the width of traffic openings through falsework can significantly affect costs, special care should be given to minimizing opening widths consistent with traffic and safety considerations. The following should be considered: 1. Staging and traffic handling requirements. 2. The width of approach roadway that will exist at the time the bridge is constructed. 3. Traffic volumes and percentage of trucks. 4. Vehicular design speed. 5. Desires of local agencies. 6. Controls in the form of existing facilities. 7. The practical problems of falsework construction. 8. Consideration of pedestrian requirements.

B. Stage construction required. Stage construction must be detailed on the plans. Construction joints or hinges would be required. C. Falsework openings required. The size and number of openings must be shown. General discussions and a table of falsework openings are covered under "Falsework Clearances". 903.02

FALSEWORK CLEARANCES

FALSEWORK USE

When traffic must pass through the construction site, three possible conditions exist. Condition 2.A. is limited to sites which can be spanned by precast members or where steel is competitive in cost. The staged construction option of Condition 2.B. is not always feasible while the presence of a hinge is a permanent disadvantage. Condition 2.C. is used for all other cases when it is necessary to route traffic through the construction site. The elimination of permanent obstructions by using longer spans and eliminating shoulder piers will usually outweigh objections to the temporary inconvenience of falsework during construction.

The minimum width of traffic openings through falsework for various lane and shoulder requirements shall be as shown in Table 900.01. The resulting falsework span shown in Table 900.01 is the minimum span. When temporary concrete barrier is used, 0.6 meters of safety margin per side is allowed for deflection. When blocked-out "W" beam is used, 1.2 meters of safety margin per side is allowed for deflection. The normal spans may be reduced or increased if other forms of protection are used depending on the required space for installation and deflection. The actual width of traffic openings through falsework and the resulting falsework span to be used in design shall be determined by the Abu

Part 3 900-3

ROADWAY DESIGN MANUAL – Roads and Bridges Dhabi Roads Section Project Manager and shall be stated in the Bridge Selection Report. To establish the grade line of a structure spanning an existing street or highway, allowance must be made for depth of falsework, where used, to provide the clearance needed to permit traffic through the work area during construction. The minimum allowances to be made for depth of falsework shall be as shown in Table 900.02 and shall be based on the actual falsework openings determined by the Abu Dhabi Roads Section Project Manager. The minimum vertical clearance for falsework over freeways shall be 4.50 meters.

Where the vertical falsework clearance is less than 4.50 meters, advance warning devices shall be specified or shown on the plans. Such devices may consist of flashing lights, overhead signs, over-height detectors or a combination of these or other devices. A standard insert sheet has been developed for the details of the over-height detectors or safety beams. Providing for these devices in the specifications or on the plans shall be the responsibility of the Abu Dhabi Roads Section Project Manager. Note to bridge designer: Special consideration shall be given to limit the maximum allowable tension in a precompressed tensile zone of posttensioned box girder bridges supported on falsework with large openings.

Table 900.01 FALSEWORK SPAN REQUIREMENTS Facility to be spanned Freeway & Non-Freeway

NOTES: (1)

Detour No. Lanes 1 2 3 4

Roadway Shoulder Widths (meters) 0.6 & 0.6 0.6 & 0.6 0.6 & 0.6 0.6 & 0.6

Minimum Width Resulting Falsework Span (1) of Traffic Temporary Blocked-out Opening (1) Conc. Barrier "W" beam (meters) (meters) (meters) 4.8 7.2 8.4 8.4 10.8 12.0 12.0 14.4 15.6 15.6 18.0 19.2

Traffic Opening and Falsework Span are measured normal to detour centerline.

Table 900.02 FALSEWORK DEPTH REQUIREMENTS 7.2 8.4 10.8 12.0 14.4 15.6

Falsework Opening (meters) Minimum Required Falsework Depth(mm) Max 3365 kg/m 485 per girder line 3365 - 4580 kg/m 510 per girder line

18.0

19.2

510

585

815

915

1070

1095

1145

560

815

890

1070

1120

1145

1170

NOTES: 1. DL based on 2550 kg/m3 concrete. 2. Table 900.02 is based on the superstructure concrete being designed for zero tensile stress at the falsework openings. Superstructures designed with concrete tensile stresses can significantly increase the required falsework depths shown in the table and amount of falsework required. 3. Structures with greater than 4580 kg/m Dead Load per girder line will require special considerations for required falsework depths.

Part 3 900-4


904.01

5.

CONSTRUCTION JOINT GUIDELINES FOR BRIDGE CONSTRUCTION GENERAL

The type of structure and method of construction, combined with sound engineering judgment, should be used in determining the number and location of superstructure construction joints. The use of construction joints should be minimized for ease of construction and subsequent cost savings. Some items which should be considered are: 1. Method of construction - earthen fill falsework, conventional falsework or girder bridge without falsework. 2. Phase construction because of physical constraints such as traffic handling. 3. Span length and estimated rotation and deflection. 4. Degree of fixity at abutments and piers. 5. Effects of locating a construction joint in a region of negative moment. 6. Volume of concrete to be poured without a joint. 7. Consequences of continuous pour, including adverse effects caused by a breakdown during the pour. Some important requirements regarding construction joints contained in the Standard Specifications are as follows: 1.

2.

3.

4.

The sequence of concrete placement shall be as shown on the project plans or as approved by the Engineer when not shown on the project plans. The rate of concrete placement and consolidation shall be such that the formation of cold joints within monolithic sections of any structure will not occur. The rate of concrete placement for major structures shall not be less than 27 cubic meters per hour unless otherwise specified or approved in writing by the Engineer. Placement of the deck concrete shall be in accordance with the placing sequence shown on the project plans.

6.

7.

904.02

The Contractor shall submit drawings showing the placement sequence, construction joint locations, directions of the concrete placement and any other pertinent data to the Engineer for his review. The drawing shall be submitted at least four weeks prior to the date of deck placement. Construction joints shall be placed in the locations shown on the project plans or as approved by the Engineer. All construction joints shall be perpendicular to the principal lines of stress and in general located at points of minimum shear and moment. LONGITUDINAL CONSTRUCTION JOINTS

Longitudinal construction joints in bridge decks and/or superstructures should be identified as optional unless required by construction phasing. The optional deck joints should be placed on lane lines or at center of structure. All longitudinal construction joints should be keyed. 904.03 PRECAST CONCRETE GIRDER BRIDGES Precast concrete girder bridges made continuous over supports shall have transverse construction joints placed so that the girders undergo their positive moment deflections prior to the final pour over the negative moment areas of the fixed piers or abutments. There shall be no horizontal construction joint between fixed pier diaphragm or abutment diaphragm and the deck. Girder bridges will usually require details on the plans showing a plan view with joint locations, deck pour sequence and direction of pour, if required. There should be a minimum of 12 hours between adjacent pours. A continuous pour from abutment to abutment will not be allowed. Construction joints where required should be parallel to the centerline of the pier. Their location will be near the point of minimum dead load plus live load moment and shear. This distance is generally one-quarter of the span length from the pier if the adjacent spans are approximately equal length.

Part 3 900-5


the pier. Their location should be near the point of dead load counterflexure.

STEEL GIRDER BRIDGES

The effects of uplift and allowing a continuous pour should be considered when developing deck pour schedules for multi-span continuous steel girder bridges. The required rate of pour should be compared to the quantity of concrete to be placed and the potential for poured sections to set up and develop tensile stresses from pours in adjacent spans shall be considered when determining the need for construction joints. Consideration must be given to the potential for negative moment stresses in the deck due to placement of positive moment pours in adjacent spans. Girder bridges will usually require details on the plans showing a plan view with joint locations, deck pour sequence and direction of pour, if required. Except where otherwise required, there should be a minimum of 12 hours between adjacent pours. Construction joints, where required, should be parallel to the centerline of

904.05

CAST-IN-PLACE BOX GIRDER BRIDGES

Box girder bridges made continuous over supports shall have transverse construction joints placed so that the webs undergo their positive moment falsework deflections prior to the final pour over the negative moment areas of the fixed piers or abutments if the superstructure formwork is supported on conventional falsework. The transverse construction joints may be omitted if the superstructure formwork is supported on earthen fill. The webs and all diaphragms should be poured concurrently with the bottom slab. Transverse construction joints where required should be parallel to the centerline of the pier. Their location near the inflection point is generally one-quarter of the span length from the pier if the adjacent spans are approximately equal length.

Part 3 900-6

ADM Roadway Design Manual

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