Traffic Engineering

FUNDAMENTALs OF TRAFFIC ENGINEERING

FUNDAMENTALs OF TRAFFIC ENGINEERING Ricardo G. Sigua

THE UNIVESITY OF THE PHILIPPINES PRESS E. de los Santos St., UP Campus, Diliman, Quezon City 1101 Tel. No.: 9253243, 926-6642/ Telefax No.: 9282558 e-mail: [email protected] © 2008 by Ricardo G. Sigua All rights reserved. No copies can be made in part or in whole without prior written permission from the author and the publisher.

The National Library of the Philippines CIP Data Recommended entry: Sigua, Ricardo G. Fundamentals of traffic engineering / Ricardo G. Sigua. – Quezon City: The University of the Philippines Press, c2008. 346 p.; 23 cm. 1. Traffic engineering – Philippines. 2. Traffic safety – Philippines. 3. Traffic regulations - Philippines I. Title. HE365.5P5 388.312’09599 2008 P074000094 ISBN 978-971-542-552-0 Book Design by Zenaida N. Ebalan Printed in the Philippines by EC-tec Commercial

Contents PREFACE 1. INTRODUCTION 1.1. Background 1.1.1. Road Transportation Network 1.1.2. Public Transportation 1.1.3. Traffic Management 1.1.4. Pedestrian Facilities 1.1.5. Vehicle Registration 1.1.6. Insurance 1.1.7. Driving License 1.1.8. Driver Apprehensions 1.1.9. Driving Schools 1.1.10. Traffic Enforcement 1.1.11. Legislative Framework 1.2. Transportation and Traffic Engineering Practice 1.2.1. Definitions 1.2.2. Traffic engineering in the Philippines References 2. TRAFFIC MANAGEMENT 2.1. Introduction 2.2.Traffic Regulations 2.2.1. Effective Traffic Regulation 2.2.2. Three Elements of the Road System 2.3.Traffic Control Devices 2.3.1. Four Elementary Requirements of Every Traffic Control Device 2.4.Traffic Signs and Markings 2.4.1. Elements of Design 2.5.International Standard traffic Signs 2.5.1. Warning Signs 2.5.2. Priority Signs 2.5.3. Prohibition Signs 2.5.4. Obligatory Signs 2.5.5. Other Prescription Signs

2.5.6. Information Signs 2.5.7. Direction Signs 2.5.8. Additional Information 2.6. Pavement Markings 2.6.1. Function and Limitations of Pavement Markings 2.6.2. Legal Authority 2.6.3. Standardizations 2.6.4. Types of Markings 2.6.5. Materials 2.6.6. Color 2.6.7. Types of Lines 2.6.8. Width of Lines 2.6.9. Messages 2.6.10. Symbols 2.7. Object Markings and Markers 2.7.1. Object Markings 2.7.2. Raised Pavement Markers Problems References 3. TRAFFIC FLOW FUNDAMENTAL 3.1.Introduction 3.2.Types of Flow 3.2.1. Major Traffic Variables 3.2.2. Other Traffic Variables 3.3. Relationship of Flow, Speed, and Density 3.3.1. Observed Relations 3.3.2. Empirical Relations 3.4. Capacity and Level of Service 3.5. Hydrodynamic and Kinematic Models of Trafic 3.6.Queuing Theory 3.6.1. D/D/1 Queuing 3.6.2. M/D/1 Queuing

3.6.3. M/M/1 Queuing 3.6.4. M/M/N Queuing 3.7.Shock Wave Problems References 4. TRAFFIC STUDIES 4.1. Introduction 4.2.Volume Studies 4.2.1. Types of Volume 4.2.2. Types of Data Collected 4.2.3. Tome of Study 4.2.4. Methods 4.2.5. Presentation of Traffic Volumes 4.2.6. AADT and ADT 4.3. Spot Speed Studies 4.3.1. Time of Study 4.3.2. Size of Samples 4.3.3. Methods 4.3.4. Analysis and Presentation of Spot Speeds 4.4.Travel Time and Delay Studies 4.4.1. Methods Problems References 5. INTERSECTION DESIGN AND CONTROL 5.1. Introduction 5.2. Basic Intersection Design Principles

5.3. Intersection Design Elements 5.4. Methods of Control of Intersection 5.4.1. Unsignalized Intersection

5.4.2. 5.4.3. 5.4.4. 5.4.5.

Roundabout or Rotary U-Turn Slots Signalized Intersection Grade Separation

5.5. Analysis of Unsignalized Intersections 5.5.1. Structure of Major Road Traffic 5.5.2. Critical Gap 5.5.3. Capacity 5.5.4. Passenger Car Equivalents 5.5.5. Reserve Capacity 5.6. Analysis and Design of Roundabouts or Rotondas 5.7. Traffic Signal Control 5.7.1. Types of Signals 5.7.2. Data Requirements for Traffic Signal Setting 5.7.3. Phase 5.7.4. Lost Times 5.7.5. Cycle 5.7.6. Allocation of Green Times 5.7.7. Capacity of Movement Approach 5.7.8. Estimation of Delay 5.7.9. Timing Diagram 5.7.10. Intersection Degree of Congestion 5.7.11. Critical Movement Analysis 5.7.12. Treatment of Left Turn Traffic 5.7.13. Left Turn Lane Length 5.7.14. Effects of left Turn Vehicles on Saturation Flow Rate 5.7.15. Coordination of traffic Signals 5.7.16. Graphical Method of Coordinating Signalized Intersections 5.7.17. Offset Problems References 6. GEOMETRIC DESIGN OF HIGHWAYS 6.1. Introduction 6.2. Design Requirements of Highways 6.2.1. Design Speed 6.2.2. Sight Distances

6.2.3. 6.2.4. 6.2.5. 6.2.6.

Minimum Radius Curvature Superelevation Design Volume Number of Lanes

6.3. Horizontal Alignment 6.3.1. Circular Curve 6.3.2. Compound Curve 6.3.3. Reverse Curve 6.3.4. Broken Back Curve 6.3.5. Easement Curve or Clothoid 6.4. Vertical Alignment 6.4.1. Properties of Parabolic Vertical Curve 6.4.2. Types of Vertical Curves 6.4.3. General Equation of Vertical Curve 6.4.4. Sight Distances at Vertical Curve 6.4.5. Sight Distances at Crest Vertical Curve 6.4.6. Sight Distances at Sag Vertical Curve Problems References

7. ROAD SAFETY AND TRAFFIC ACCIDENT ANALYSIS 7.1. Introduction 7.2. Assessment of Road Safety 7.2.1. Accident per Population 7.2.2. Accident per Registered Vehicles 7.2.3. Accident Definition 7.2.4. Road Accident Reporting 7.2.5. Present Situation 7.2.6. Key Socioeconomic Indicators 7.2.7. Accidents at Intersections 7.2.8. Accident Rates for Intersections 7.2.9. Accident Rates for Road Sections 7.2.10. Accidents by Time of Day 7.3. Identifying Hazardous Locations or Blackspots 7.3.1. Classic Statistical Method 7.3.2. Rate Quality Control 7.3.3. Setting Benchmark Method

7.4. Response of Safety 7.4.1. The Inter-agency Road Safety Committee and the National Road Safety Committee 7.4.2. Agencies and Institutions Involved in Road Safety 7.5. Initiative of Road Safety 7.5.1. Imposing Motor Vehicle User’s Fee 7.5.2. Motor Vehicle Inspection System 7.5.3. Seat belt Law 7.5.4. Banning Use of Cellular Phones and Handset Radios 7.5.5. Other Initiatives 7.6. Road Safety Issues 7.6.1. Legislative 7.6.2. Institutional 7.6.3. Technical 7.6.4. Education and Campaigns 7.6.5. Sociocultural 7.7. Cost of Traffic Accidents 7.7.1. Uses of Accident Cost Estimates 7.7.2. Approaches to Estimating Cost of Accidents 7.7.3. Determination of Cost Components 7.7.4. Estimation of Cost Components 7.8. Estimation of Average Cost of Accidents 7.8.1. Estimation of Cost of a Single Fatal Accidents 7.8.2. Estimation of Cost of a Single Serious Injury Accident 7.8.3. Estimation of Cost of a Single Minor Injury Accident 7.8.4. Estimation of Cost of a Single Property-Damage-Only Accidents 7.8.5. Summary of Average Cost of Each Type of Accident 7.9. Estimation of National Cost 7.9.1. Data Availability and Quality 7.9.2. Calculation of National Costs Problems References 8. INTRODUCTION TO TRAVEL DEMAND FORECASTING 8.1. Introduction

8.2. The Four-Step Forecasting Model 8.3. The Origin-Destination Table (OD Matrix) 8.4. Methods of Estimating Trips Generation and Attraction 8.4.1. Growth Rate Method 8.4.2. Category Analysis 8.4.3. Regression Analysis 8.5. Trip Distribution 8.5.1. Present Pattern Method 8.5.2. Model Method 8.6. Modal Split 8.6.1. The Generalized Cost 8.6.2. Disaggregate Choice Model 8.7. Route Assignment 8.7.1. The Shortest Path 8.7.2. Network Assignment Problems References 9. INTRODUCTION TO INTELLIGENT TRANSPORTATION SYSTEM 9.1. Background 9.2. Current Deployment of ITS in the Philippines 9.3. Road Pricing 9.4. Some Issues Related to Sustainable Deployment of ITS in Developing Countries 9.5. Conditions for Acceptable Deployment/Implementation of ITS in Metro Manila 9.6. Conclusion References GLOSSARY OF TERMS INDEX THE AUTHOR

This work is dedicated to . . . My Lord God Almighty – the Way (John 10:35), the light unto my Path (Psalms 119:105) My wife, Helen – my faithful journey companion (Proverbs 31: 25-28) Our children, Karen, Paul, and Luke – my arrows in my warrior hand (Psalms 127: 3-5) “And I will make all My mountains a road, and My highways will be raised up. Behold, these shall come forth from afar; and lo, these will come from the north and from the west . . .” (Isaiah 49: 11-12)

PREFACE The scarcity of books on transportation, especially those particularly relevant and appropriate to a Philippine setting, as long been a legitimate compliant of students educators, and practitioners. While it is true that transportation engineering is a young field relative to other civil engineering disciplines, the demand for good education and training on the field has escalated due to rapid urbanization. As cities and towns grow and develop, the problem related to transport and traffic intensify in geometric proportions. To avoid costly and, at times, irreversible mistakes, a solid foundation in traffic engineering is a must. We cannot continue to rely on reactionary or trialand-error approaches to our road and traffic woes. Only through a firm grasp and systematic application of basic knowledge and theories could we truly come up with credible and effective solutions. Only through systematic evaluation and research could we discard ineffective designs, improve our skills, and upgrade our systems. The book include basic concepts that a senior civil engineering student is expected to thoroughly understand. Topics like queuing and shock wave theories are rather advanced, but the basic formulations are presented and conceptualized in simplified manner that even undergraduate students can easily comprehend. It is likewise written as a handy self-contained reference or easy guide for practicing traffic engineers. A notable recurring theme woven into all discussions is road order and safety. In the quest for efficiency, sophistication, or cost effectiveness, basic safety and orderliness must never be compromised. Accident prevention should always be the first and foremost concern in every design. Preservation of human life remains the most important goal of a good traffic engineer. We are faced with myriads of transportation and traffic problems: congestions, populations, energy, inadequate public transportation – the list is endless. Even more affluent countries are not devoid of transportation problems, in varying degrees and forms. But, universally, there is nothing more gratifying than having the field of traffic engineering help meet the needs of our communities towards acquiring not only road efficiency and also a safer and more orderly road environment. The completion of this book would not have been possible without the valuable assistance of the following: The University of the Philippines Office of the Vice President for Academic Affairs, for the textbook writing grant;

The UP College of Engineering (COE) and the UP National Center for Transportation Studies (NCTS), formerly the Transport Training Center, for having been the venue all throughout this years for my teaching and honing the substance of the basic concepts; Colleagues in the UP COE and NCTS, for their encouragement and full support as I wrote the detail of each chapter; Civil engineering professors in other universities, for stressing the need for a local book in transportation engineering; Partners in national agencies and the private sector, for providing statistics, photos and other reference materials; and The UP Press editorial staff, for the painstaking work of editing and layouting the manuscript. R. G. Sigua

1 INTRODUCTION 1.1 BACKGROUND The Philippines, a member of the Association of Southeast Asian Nations, is an archipelagic country consisting of more than 7,100 islands. With a total land area of about 300,000 sq. km, it has 81 provinces, 136 cities, and 1,494 municipalities (NSCB 2007). Metro Manila is the seat of the government and the primary center of business and trade. Other urban centers include the major cities of Cebu and Davao (see figure 1.1). The population of the Philippines is about 80 million, with a growth rate of 2.2 percent per annum. The population density stands at 227 persons/sq. km. Metro Manila comprises sixteen cities and one municipality (NSCB 2007). Its land area is 636 sq. km, and it has a population of 10.4 million. This implies that about 14 percent of the country’s population is concentrated in only 0.3 percent of the country’s land area. Its population density is about 16,000 persons/sq. km, one of the highest in Southeast Asia. The population growth rate is about 3 percent, higher than the national average (ALMEC Corp. 1999). 1.1.1 Road Transport Network Some 80 percent of domestic passenger traffic and 60 percent of freight traffic currently use the road, and 75 percent of government expenditures on transport infrastructure goes to road systems 9Abueva 2004). The Philippines has a total road length of about 161,000 km, with an average road density of 0.53 km/sq. km or 2.35 km per 1,000 people. Philippine roads are mostly made of concrete pavement. Due to heavy, overloaded trucks, pavements are often damaged, a factor that contributes to traffic accidents. Due to a long rainy season, floods occur throughout the Philippines, Floodwaters often cause damage to road pavements due to inadequate drainage. There are about 11,500 bridges in the national network (measuring about 335,500 lineal meters), of which 1,700 bridges are temporary (DPWH 2004). Metro Manila has a total road length of about 4,800 km. The major arterial roads form circumferential and radial patterns, although road expansion is seen toward the north and south

Figure 1.1 The Philippines (Metro Manila inset)

directions, following the development of Metro Manila. Figure 1.2 shows the major road network of Metro Manila with daily traffic. Many of the roads have reached their capacity. Due to traffic congestion, the average travel speed is estimated to be as low as 14 kph, with roughly one-third of the travel time wasted as idle time (Sigua 1997). A typical urban travel in Metro Manila is shown in figure 1.3. According to the 2000 study of the University of the Philippines National Center for Transportation Studies, traffic congestion in Metro Manila has caused more than P101 billion in losses. The condition of the roads in Metro Manila is generally good while it is poorer outside the metropolis.

Figure 1.3 Typical urban travel in Metro Manila 1.1.2 Public Transportation The mode of public transportation in Metro Manila is predominantly road-based, consisting largely of jeepneys and buses for primary and secondary routes, and motorized tricycles and pedicabs for feeder routes. There are about 330 bus routes and 600 jeepney routes. These

routes include those serving the adjoining areas of Metro Manila. The jeepneys cover more than 610 km of roads while buses operate mainly on about 350km of roads (ALMEC Corp 1999). Figure 1.4 shows the major bus and jeepney routes. During rush hours, the inadequate provision of public transportation becomes apparent. Many commuters can be seen standing on the carriageway while waiting for buses and jeepneys. Passengers clinging to anything at the back of jeepneys are a common sight. 1.1.3 Traffic Management Traffic control devices such as traffic signs and markings generally follow the international standard, the Philippines being a signatory to the Vienna Convention in 1968. However, many of the signs installed conform neither to color nor shape as provided for in the standard. The number of traffic signs installed is generally insufficient. In highly urbanized areas, these signs can hardly be recognized, much less read, as they compete with giant billboards in terms of visibility and craftsmanship. Traffic signals are commonly installed at major intersections in many cities and towns in the Philippines although the number is still inadequate. Oftentimes, these signals do not provide display phase exclusive for pedestrians. In Metro Manila, there is a growing concern about the safety of pedestrians due to the closure of intersections and with the U-turn slot scheme replacing the control of traffic signals. Pedestrians have practically no opportunity to cross the road because of the “uninterrupted” flow of traffic. Without traffic signals controlling the traffic flow at intersections, driving has become riskier because of frequent swerving/weaving. There is an urgent need to evaluate the effectiveness of the scheme, which has the sole purpose of improving speed along the arterials without consideration of safety.

Figure 1.4 Major bus and jeepney routes

1.1.4 Pedestrian Facilities Sidewalks are in relatively good condition; however, many obstructions can be found on them such as illegal vendors, electrical posts, police outpost, etc. With the sidewalk occupied, pedestrians have to walk on the carriageway. There are still very few overhead pedestrian bridges even in Metro Manila and at places where these have been constructed, pedestrians still prefer to risk their lives or limbs by crossing the road at grade level. Moreover, pedestrian overpasses are often inaccessible to the elderly and the handicapped.

Figure 1.5 A pedestrian overpass in Metro Manila (Photo taken by the author)

1.1.5 Vehicle Registration The registration of vehicles in the Philippines is handled by the Land Transportation Office (LTO), a line agency of the Department Transportation and Communication (DOTC). Table 1.1 shows the number of registered motor vehicles in the Philippines in 2002. The number of utility vehicles or jeepneys has a share of 37 percent. The number of motorcycles has increased tremendously in the last three years due to the influx of cheaper models into the country. It reached the 1.5 million mark in 2002. However, this number accounts for both the motorcycles (MCs) for private use and tricycles (TCs) for public transport use. There is therefore a need to separate the categories since they serve completely different purposes.

Type Cars UV SUV Trucks Buses MC/TC TOTAL Source: LTO 2005

Table 1.1 Total registration of motor vehicles for 2002 Number 749,553 1,554,619 97,695 257,774 33,915 1,470,383 4,163,939

% 18.00 37.34 2.35 6.19 0.81 35.31 100.00

About 40 percent of the total numbers of vehicles are registered in Metro Manila. Motor vehicles are classified as follows: 

Private vehicles – refers to motor vehicles owned by private individuals or companies and are not intended to be used for hire.



For hire vehicles – refers to motor vehicles authorized to be used as public vehicles by virtue of a franchise granted by the Land Transportation Franchising and Regulatory Board (LTFRB).



Official/Government Vehicles – refers to motor vehicles owned by the Philippine government.



Diplomatic Vehicles – refers to motor vehicles owned by a foreign government or by their diplomatic officials in the Philippines.

1.1.6 Insurance Motor vehicle owners are required to obtain insurance covering third-party liabilities. The minimum insurance to be paid to victims of traffic accidents (fatal) was P50, 000 in 2002.

The Insurance Surely Association of the Philippines under the Office of the Insurance Commissioner accredited 112 insurance companies all over the Philippines by 2002. It regulates the industry to prevent the proliferation of fly-by-night insurance companies. 1.1.7 Driving License The issuing procedure of driving license in provided for under Republic Act (RA) 4136. The LTO has the full responsibility for issuance of driving licenses. There are three types of driving licenses: student driver’s permit, nonprofessional driver’s license, and professional driver’s license. a. Student driver’s permit The applicant must be at least sixteen years old and must be physically and mentally fit to operate a motor vehicle. He or she must be able to read and write in Filipino or English. b. Nonprofessional driver’s license New applicant must be at least seventeen years old and must be a holder of a valid student permit for at least one month. He or she must be physically and mentally fit to operate a motor vehicle, and must not be a drug user or an alcoholic. c. Professional driver’s license New applicant for professional driver’s license must be at least eighteen years old and is required to submit a valid nonprofessional driver’s license or a valid student driver’s permit that is used for at least five months. He or she must not be a drug user or an alcoholic. The requirement of having a medical examination and drug test was introduced only very recently.

Driving license requirements The holder of a student driver’s permit is only allowed to operate a motor vehicle if accompanied by a licensed driver who is liable for any damage caused by the student driver’s operation of the motor vehicle. A student driver’s permit is good for only one year while the nonprofessional and professional driver’s licenses are valid for three years, expiring on license holder’s birth month. License holders are required to renew their license before the expiry date.

Written and practical examinations Applicants for nonprofessional and professional driver’s licenses are required to pass both written and practical examinations.

The written examination is given to gauge the applicant’s knowledge of traffic rules and regulations based on the Traffic Code, safe driving practices, and the mechanics of motor vehicles. The written test for nonprofessional driver’s license applicants has forty questions, and candidates must be able to answer at least thirty questions correctly. In the case of the professional driver’s license applicants, sixty questions are given, and applicants must be able to get at least forty-five correct answers to pass the test. The practical examination is given to test a candidate’s ability to park a vehicle properly, to start on slope, etc. The total number of professional licenses, nonprofessional licenses, and student permits issued in 2002 was about 2.9 million. The breakdown is shown in figure 1.6.

Professional

Non-professional

Student permit

Figure 1.6 Breakdown of driver licenses and permits issued in 2002

1.1.8 Driver Apprehensions There seems to be an increasing trend in the number of drivers apprehended (table 1.2). This could be attributed to the concerted efforts of the different agencies (the Land Transportation Office, the Metro Manila Development Authority [MMDA], and the Philippine National Police – Traffic Management Group [PNP-TMG]) in apprehending violators over the past years.

Table 1.2 Number of apprehended drivers Year 1999 2000 2001 2002

Total 480,122 475,626 570,748 612,477

Source: LTO 2005 As to the type of apprehensions, most of these are fines for violating traffic rules and regulations (table 1.3)

Table 1.3 Breakdown of types of driver apprehension (1999-2002) Type Number % Fined 594,126 92.89 Suspended license 345 0.05 Revoked license 4,447 0.70 Impounded vehicle 5,771 0.90 Others 34,933 5.46 Source: LTO 2005 1.1.9 Driving Schools Driving schools and driving instructors must have accreditation from the LTO. In 1980, the then Ministry of Transportation and Communications (MOTC) issued an order covering the rules and regulations governing the supervision and control over driving schools. Standard requirements were set fourth for driving site, school building, classrooms, library facilities, motor vehicles, instructors, and course of instruction. In 2002, about 170 LTO-accredited driving schools were in operation all over the country. 1.1.10 Traffic enforcement Traffic laws are enforced by the Traffic Management Group (TMG), the traffic division of each district police, and the LTO. In 1978, Presidential Decree (PD) 1605 was issued to centralize enforcement matters in Metro Manila to the Metro Manila Commission (MMC), now the Metro Manila Development Authority. The TMG, being a national support unit of the PNP, has traffic management offices scattered in the different regions and provinces nationwide. In selected areas or provinces, especially in highly urbanized cities/municipalities, the TMG has traffic management teams (TMTs) that are also capable of performing the functions of the TMG operational support units that are likewise based in Metro Manila. In coordination and cooperation with the MMDA for

Metro Manila and the local police units in the different regions, the TMG has at its disposal the traffic enforcement units. Each Regional Traffic Management Office (RTMO) can dispatch personnel to strategic choke points and major thoroughfares to conduct traffic direction and control to ensure the smooth flow of traffic. In Metro Manila, the TMG and the MMDA assist each other in traffic management, especially when on-going infrastructure projects cause heavy congestion. Alongside this function, the personnel of TMG render the following tasks: traffic accident investigation, and the traffic safety education through seminars and conferences, etc. 1.1.11 Legislative Framework This section discusses some of the legislations pertinent to road safety (Santiago 1980). Republic Act 4136, otherwise known as the Land Transportation and Traffic Code, provides for the system of registration of motor vehicles, checks on accessories of vehicles, and defines road traffic rules and regulations. Commonwealth Act 146, otherwise known as Pubic Service Act, rests on the regulatory body (LTFRB) the power to compel any public service provider to furnish safe, adequate, and proper service as regards the manner of furnishing the same as well as the maintenance of necessary materials and equipment. Executive Order (EO) 125 reorganized the then Ministry of Transportation and Communications into a Department and defined its powers and functions, including the establishment of the Land Transportation Office as the sectoral agency responsible for implementing and carrying out policies, rules, and regulations governing the land transportation system of the country. Executive Order (EO) 202 created the Land Transportation Franchising and Regulatory Board with the main function of regulating the land transport industry pursuant to the Public Service Act. Republic Act 6975 established the Department of the Interior and Local Government (DILG), including the creation of the PNP under which the Traffic Management Group has been reorganized as the traffic enforcement arm of the PNP covering national roads.

1.2TRANSPORTATION AND TRAFFIC ENGINNERING PRACTICE 1.2.1 Definitions Transportation engineering is a filed or branch of civil engineering that deals with the application of technology and scientific principles to the planning, functional design, operation, and management of facilities for any mode of transportation in order to provide for the safe, rapid, comfortable, convenient, economical, and environmentally compatible movement of people and goods.

On the other hand, traffic engineering is that phases of transportation engineering that deals with the planning, geometric design, and traffic operations of roads, streets and highways, their networks, terminals, abutting lands, and relationships with other modes of transportation (Evans 1950). In the United States, it was in 1921 when the title “traffic engineer” was first recognized, although a number of traffic engineering-related activities were already going on. Table 1.4 shows some of these activities:

Table 1.4 Milestones in the developing profession of traffic engineering Year Activity 1904 Traffic survey methods were being employed. 1907 Pedestrian islands were used in San Francisco. 1908 The first driver’s license law was adopted. 1911 White-painted pavement center lines were first applied. 1915 Origin-destination studies and accident spot maps were first used. 1916 Speed and delay study was first made by observing traffic from a high building; pedestrian regulation and “no left turns” were prescribed; curb parking was prohibited to facilitate traffic movement. Source: Evans 1950 The use of traffic signals for controlling traffic came much earlier. The first recorded use of traffic signals was in 1868 in Great Britain. The signals were illuminated by town gas. However, the use of gas was discontinued after an explosion incident. The development of traffic signal technology is shown in table 1.5.

Year 1868 1910 1922 1926 1927 1928 Source: Evans 1950.

Table 1.5 Development of traffic signal control Activity First traffic signal in Great Britain (illuminated by gas) Manually operated semaphore signals Idea of timing signals for progressive movement First automatic traffic signals in Great Britain Earliest known application of time-space diagram coordination First traffic-actuated signals

for

In 1930, the Institute of Traffic Engineers (ITE) was founded, and traffic engineering as a profession was finally officially established and defined. The society played a key role in promoting the profession through advanced training, research studies, standardization, laws, and application of traffic engineering techniques (Evans 1950).

1.2.2 Traffic Engineering in the Philippines The traffic engineering practice in the Philippines is still new. Most intersections were previously controlled by traffic police officers or by manually operated traffic signals. Outside Metro Manila, manually operated semaphore signals displaying STOP or GO message were installed on top of police outposts located at the center of the intersection. In 1977, the Traffic Engineering and Management (TEAM) Project first implemented an area traffic control system in Metro Manila. It was almost at the same period when the Traffic Control Center, later renamed as the Traffic Engineering Center (TEC), was established. The center was responsible for the implementation of various traffic engineering and management measures such as traffic signalization, geometric improvement of intersections, etc. In 1976, the Transport Training Center (TTC) was established in the University of the Philippines with assistance from Japan through the Japan International Cooperation Agency (JICA). TTC started its training program in 1978 in the fields of traffic engineering, transportation planning, and traffic management for traffic law enforcers. TTC was renamed as the National Center for Transportation Studies and became a regular unit of UP Diliman in 1993, with research and support to graduate programs in the fields of transportation engineering and transportation planning as additional functions.

REFERENCES Abueva, Jose V., ed, 2004. The Macapagal-Arroyo presidency and administration: Record and legacy (2001-2004). Vol. 1. Quezon City: UP Press. ALMEC Corporation. 1999. Metro Manila Urban Transportation Integration Study (MMUTIS) final report. Department of Public Works and Highways (DPWH). 2004. Infrastructure atlas 2004. Evans, Henry K., ed. 1950. Traffic engineering handbook, Second ed, New Haven, Connecticut: Institute of Traffic Engineers. Land Transportation Office, 2005. Statistics, Unpublished. National Center for Transportation Studies (NCTS). 2000. A study on cost of traffic congestion in Metro Manila, Quezon City: NCTS. National Statistical Coordination http://www.nscb.gov.ph.

Board

(NSCB).

2007.

NSCB

website.

Santiago,Mariano R., ed. 1980. A compilation of edicts related to the land transportation system of the Philippines. Quezon City: Bureau of Land Transportation. Sigua, Ricardo G. 1997. Development of driving cycle for Metro Manila. Journal of the eastern Asia Society for Transportation Studies 2, no 4. Seoul: Eastern Asia Society for Transportation Studies (EASTS).

2 Traffic management 2.1 INTRODUCTION Traffic management is a term used to embody the activities undertaken by a highway transportation agency to improved roadway system safety, efficiency, and effectiveness for both providers and consumers of transportation services. There are two distinct types of traffic management. The first one utilizes traditional traffic engineering tools or simple devices to regulate and control traffic. The second relies more on advanced technology through the use of Intelligent Transportation Systems (ITS) advanced of ITS has been primary goal of many developed countries. However, it is not uncommon in both developed and developing countries to have a combination of conventional methods and ITS applications. An introduction to ITS is provided in chapter 9. 2.2 TRAFFIC REGULATIONS Many individuals feel that traffic control measures are an encroachment on their individual driving right. It must be stressed, however, that driving is not a right but a privilege. It is therefore necessary to show that restrictions are for the general welfare, and it must be demonstrated that regulations do not curtail the rights or actions of the majority. Traffic regulation must cover all aspects of the control of both vehicle (registration, ownership, mechanical fitness, accessories, size, weight) and driver (age, ability to operate specific types of vehicles, financial responsibility). Traffic regulation must be reasonable and effective. This can only be achieved through careful study. Facts must be sought through the conduct of traffic studies, accident analysis, keeping driver record and other data. All traffic regulation are dependent upon the laws of the states and local governments, especially the ordinances of cities. Legislative bodies and traffic authorities must keep in mind that unreasonable restrictions or regulations are not likely to last very long. 2.2.1 Effective Traffic Regulation There are fundamental requirements for traffic regulation to be effective. These are as follows:

a. Regulation should be rational. Irrational regulations cannot be enforced except by tremendous effort and expense. Social, economic, and human problems must be considered. If the habits of a community are greatly at variance with the regulations, success cannot be attained for any substantial period of time. b. Regulation should be developed progressively. Regulations must be planned over a long period of time, and the effect must be carefully observed so that alterations can be made as experience dictates, experience shows that abrupt changes in regulation often lead to increase in the occurrence of traffic accidents. c. Regulations alone often are not enough. Regulation constitute but one approach to the overall traffic problem. When public acceptance is poor and enforcement is lax, regulation may be totally ineffective. They must be used in conjunction with control devices, overall highway planning and design, and administrative policies. 2.2.2 Three Element of Road System The road system consist of the following: a. The road b. The vehicle c. The driver Figure 2.1 suggests a balance among the three elements, i.e., a breakdown or deficiency in one can lead to the failure of the entire system. Road/ Environment

Vehicle

Human/ Driver

Figure 2.1 Interaction of the three elements of the road system The road and vehicle may be subject to constant change and improvement. However, in a given period of time, they may be considered inflexible. The major portion of existing regulations

are therefore aimed at the driver. Worldwide, licensing has become the most effective way of controlling the number of drivers on the road. It should be used, therefore, to influence drivers to become familiar with the rules of the road. This is especially true for the Filipino drivers, considering the most accidents have been attribute to them. For vehicles, a number of controls exist, the most effective of which is vehicle registration. Others are checks on equipment and accessories (lights, bells, mirrors, helmets, etc.), and vehicle’s dimensions and weight. Currently, the Motor Vehicle Inspection System (MVIS) is being revitalized and expanded to cover the whole country. 2.3 TRAFFIC CONTROL DEVICES Traffic control devices are means by which the road user is advised as to detailed requirements or conditions affecting road use at specific places and times so that proper action may be taken and accident or delay avoided. There are three distinct functional groups of traffic control devices: a. Regulatory devices These have the authority of law and impose precise requirements upon the actions of the road user. b. Warning devices These are used to inform road users of potentially hazardous roadway conditions or unusual traffic movements that are not readily apparent to passing traffic. c. Guiding devices These are employed simply to inform the road user of route, destination, and other pertinent information. 2.3.1 Four Elementary Requirements of Every Traffic Control Device To be effective, every traffic control device must be able to meet the following requirements (FHWA 1988): a. b. c. d.

It should compel attention. It should be convey a simple clear meaning at a glance. It should allow adequate time for easy response. It should command the respect of the road users for whom it is intended.

Every traffic control must meet all these requirements in logical sequence. The effectiveness of a sign or marking normally depends on its size, color contrast, shape (simple, regular shapes), relative position, and maintenance to compel attention. To convey a clear meaning, the shape, color, and message must be well understood. The message should be kept as short as practicable because not more than three familiar words can be conveyed at a glance. After capturing the clear meaning of the device, it should provide adequate time for response.

Simpler message like STOP or YIELD requires only a second, while multiple choice (as in destination or guide sign) may require three to four seconds. Finally, all these requirements – the design features of size and brightness, position allowing time for response, properly maintained control device – should command the respect of road users. Thus, shabby, ill-kept sign must be discarded and replaced. 2.4 TRAFFIC SIGNS AND MARKINGS Traffic signs are employed more frequently than any other devices to regulate, warn, or guide road users. Traffic markings normally consist of lines, patterns, words, symbols, reflectors, etc. they may be considered as specialized types of traffic signs in which the message is in contrast with the color and brightness of the pavement or other background. Philippine traffic signs conform to the 1968 Vienna Conventions of the United Nations on Road Traffic and Road Signs, which the country officially adopted on June 6, 1973. Traffic signs are necessary to give information as to routes, directions, destinations, etc. their function becomes more relevant when used to warn road users of hazards and regulate any prohibitive action at specific places and/or at specified times. To ensure uniformity, traffic signs shall be installed only by a duly authorize public body or official for the purpose of guiding, regulating, and warning traffic. In case of temporary construction work, however, special permission is given to contractors or utility companies to install signs to protect the public provided that such signs conform to the set standards. Traffic signs are normally of fixed/permanent type although some variable signs have been employed and have become useful in locations where traffic and environment conditions often change. Traffic signs are classified depending on their intended uses: a. Informative: the signs are intended to guide users while they are traveling. b. Regulatory: the signs are intended to inform users of special obligations, restrictions, or prohibitions with which they must comply. c. Warning: these signs are intended to warn users of a danger on the road and to inform them of its nature. 2.4.1 Elements of Design Uniformity in design includes shape, color, dimension, symbols, wording, lettering, and illumination or reflectorization. 

Shapes Shapes of signs are standardized as follows: a. Equilateral triangular shape with one side horizontal shall be used for danger warning signs. b. Round shape shall be used for regulating traffic.

c. Rectangular shape shall be used for informative signs. d. Octagonal shape shall be used for STOP signs only. e. Inverted equilateral triangle shall be used for YIELD signs only. 

Color Danger warning signs shall have a yellow or white background with black symbols and red borders. Prohibitory signs and restrictive signs shall have a white background with black symbols and red border. Mandatory signs with the exception of STOP and YIELD signs shall have a blue background and white symbols. STOP signs shall have a red background and white symbols. YIELD signs shall have a yellow background and red border. Informative sign shall have a white or light-colored symbols on a dark-colored (blue or black) background or a blue or dark-colored symbol on a white or light-colored background.

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Size The minimum dimension of signs depends upon the intended applications. Large sizes are necessary at wider roadways and on high speed highways. According to section 2.5 of the DPWH Highway Safety Design Standards Part 2: Road Signs and Pavement Markings Manual, regulatory signs are of four sizes based on the speed of the facility as follows: a. b. c. d.

A for urban low-speed roads B for rural roads with speed limit between 60 kph and 70 kph C for high-speed rural highways D for expressway

In the case of a STOP or YIELD sign, for example, table 2.1 below should be followed: Size

Dimension (mm)

A

600 x 600

B

750 x 750

C

900 x 900

Source: DPWH 2004

The reader is advised to refer to the DPWH manual for the dimensions of various traffic signs and for other details – letter, symbol, border, bar sizes, etc. 

Illumination and reflectorization Signs are intended to convey messages during both daytime and nighttime. During hours of darkness, this can be achieved through illumination or by using reflective materials for signs.

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Placement and height of signs In general, signs shall be mounted approximately at right angles to the directions, and facing the traffic they intend to serve. Mounting signs at exactly right angle must be avoided especially on roads following the east and west directions as the sun’s brightness reflecting on the signs will be too glaring for the drivers. However, there may be no standard location for traffic signs. Each location must be carefully studied so as to achieve the most advantageous position. Signs are generally placed in the right side of the roadway. On wider roads, overhead signs are often necessary. On roads with medians, signs may be placed on both sides. Signs may also be placed on channelized islands. a. Lateral placement On uncurbed roads in the rural areas, the sign should be at least 60 cm clear of the outer edge of the road shoulder, the line of guideposts, or face of guardrails. The clearance should not be less than 2 m nor more than 5 m from the edge of the traveled way, except for large guide signs on expressways where ample clearance may be required. (see figure 2.2). In urban areas, signs soul be located away from the face of the curb not less than 30 cm but not more than 1 m. if curb is mountable or semimountable, the minimum clearance should be 50 cm. On uncurbed roads, the distance given for rural areas shall be used. b. Height In rural areas, the height of the sign should normally be between 1 m and 1.5 m above the nearest edge of traveled way. For intersection direction signs, the height should be increased to 2 m. Final height is dictated by visibility factor as the sign should be mounted clear of vegetation and it must be clearly visible under headlight illumination at night (see figure 2.2). On curbed roads such as in urban areas, the signs should be mounted at a minimum of 2 m above the top of the curb to prevent obstruction to the pedestrians.

Figure 2.2 Height and lateral placement of signs c. Location of advance warning signs In urban areas, warning signs should be placed no less than 30 m but no more than 100 m in advanced of the hazardous area, while in rural areas they should be placed no less than 75 m but no more than 225 m ahead of the hazardous area. The final location shall be determined based on the nature of the hazard, reaction time, and operating speed in the area. 2.5 INTERNATIONAL STANDARD TRAFFIC SIGNS 2.5.1 Warning Signs The Vienna Convention allows two forms for the warning sign – one is triangular in shape with a red border and the other is diamond in shape (table 2.2). Upon signing the convention, the signatory has to state which shape should be adopted. In the Philippines, the first form is the one being used although the second may still be found in the rural areas. The coloring may also differ in each form. However, the choice of color is left to the discretion of the signing body. Examples of warning signs are shown in table 2.3.

Table 2.2 Shapes and colors of warning signs

Table 2.3 Examples of Warning signs

2.5.2 Priority sign Priority sign have various forms. The two most commonly used priority signs are the STOP and Yield sign (table 2.4). Table 2.4 Example of priority signs

2.5.3 Prohibition Signs Prohibition signs are round with a red border and either a white or a yellow background. Access restrictions signs can have a red bar from low right to top left. Parking prohibitions have a blue background. The signs that signal the end of a prohibition are white or yellow with a small black border and a black bar from left below to right top. The bar can be replaced by a series of small bars. In addition the symbol for which the end of prohibition is intended is given in gray. Examples of prohibition signs are shown in table 2.5. Table 2.5 Examples of prohibition signs

Table 2.5 (continued)

2.5.4 Obligatory Signs The obligatory signs are round and in blue color. Examples are shown in table 2.6. Table 2.6 Examples of obligatory signs

Table 2.6 (continued)

2.5.5 Other Prescription Signs These signs are, in general, rectangular with either blue base with a white foreground, or with a light base with a dark foreground. These signs give prohibitions, obligations, or danger messages for particular lanes on a multilane road. Each lane is represented by an arrow, to which the appropriate sign is affixed. Table 2.7 shows some examples. The background color blue is used for major roads, white for minor roads and within built-up areas, and yellow for road works. Table 2.7 Examples of prescription signs

Table 2.7 (continued)

2.5.6 Information Signs These signs are rectangular with a white or yellow plate with the symbol that stands for the serviced involved, the signs can be either blue or green. Examples are shown in table 2.8.

Table 2.8 Examples of information signs

2.5.7 Direction Signs A profusion of colors and forms is available. In general the forms shown must be adopted, and in some cases even the color shown must be used and not be changed. Table 2.9 Examples of directional signs

2.5.8 Additional Information These signs are small and rectangular; they supplement the information on the main sign (table 2.10). Table 2.10 Examples of supplemental signs

2.6 PAVEMENT MARKINGS 2.6.1 Functions and Limitations of Pavement Markings A system of clear and effective pavement markings is essential for the guidance and control of vehicles and pedestrians. They take the form of lines, symbols, messages, or numerals, and may be set into the surface of, applied upon, or attached to the pavement. In some cases, pavement markings are used as a supplement to other traffic control devices, such as traffic signals and road signs. In other instances, they may simply guide traffic or give advance warning, or they may impose restrictions supported by traffic regulations. Pavement markings have some definite limitations: a. They are subject to traffic wear and require proper maintenance. b. They may not be clearly visible if the road is wet or dusty (e.g., near shoulder edge or median). c. They may be obscured by traffic. d. Their effect on skid resistance requires careful choice of materials.

e. They cannot be applied on unsealed roads. Despite these limitations, they have the advantage under favorable conditions of conveying warning message or information to drivers without diverting their attention from the road. 2.6.2 Legal Authority Markings shall only be applied and/or removed by the Department of Public Works and Highways (DPWH) or an authority to which these powers are delegated. All line-marking plans must be approved by the DPWH before installation. 2.6.3 Standardization As is the case with all other traffic control devices, it is imperative that markings be uniform so that they may be recognized and understood instantly by all drivers. Manuals are available from the DPWH, and on request, it will furnish traffic authorities, road markers, material suppliers/manufacturers, and similarly interested agencies, detailed drawings of the standard designs and locations. 2.6.4 Types of Markings Markings are classified into the following groups: 

Pavement and curb markings a. Longitudinal lines are those laid in the direction of travel. These include Center line, Lane Line, Double Yellow Line, “No-Passing” Zone Markings, Pavement Edge Line, Continuity Lines, and Transition Line. b. Transverse lines are those laid across the direction of travel. These include Stop Line, Yield (Give Way) Lines, and Pedestrian Crossing Markings. c. Other lines, which include Turn Lines, Parking Bays, Painted Median Islands, and Bus & PUJ Lane Lines. d. Other markings, which include Approach Markings to Islands and Obstruction, Chevron Markings, Diagonal Markings, Markings on Exit and Entrance Ramps, Curb Markings for Parking Restrictions, Approach to Railroad Crossing, Messages and Symbols and Pavement Arrows.



Object Markings a. Object within the roadway b. Object adjacent to the roadway

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Reflector Makings a. Retro-reflector raised pavement markers b. Hazard markers c. Delineators

2.6.5 Materials Road markings should be of nonskid materials and should not protrude more than 6 mm above the level of the carriageway. Raised pavement markings should not protrude more than 15 mm above the level of the carriageway. The following are the commonly used material for road markings: 

Paint Paint with or without glass beads embedded or premixed can be applied either by hand or with lie marking machines. For proper reflectorization at night, the amount of glass beads used should be no less than 0.45 kg and no more than 0.50 kg per liter mixed paint.



Thermoplastic materials Use of thermoplastic materials with or without reflective properties is recommended at location subject to extreme traffic wear. The average service life of thermoplastic materials has been experienced to be equivalent to eight times that of beaded traffic paints.



Precut sheeting Precut materials both with or without reflective properties are used. It is usually in adhesive tape form, with aggregate, pigment, and plastic rubber combined on one side and adhesive on the other side.



Raised pavement markers These are studs of plastic, ceramic, aluminum, cast iron, etc. that are embedded into the carriageway or attached to the road surface with adhesive. They may be reflective or nonreflective.

2.6.6 Color The color of pavement markings shall be white, except for the alternative uses of yellow in the following cases: a. b. c. d. e.

Double yellow “no-passing” lines Unbroken portion of “no-parking” lines Curb markings for prohibition of parking On islands in line of traffic Bus and PUJ lanes

Black may be used in combination with white or yellow in hazard markers to warn drivers at locations where the protruding objects – such as bridge piers, traffic islands, or other permanent objects – on or near the roadway. However, the use of black does not establish it as a standard color for pavement marking. 2.6.7 Types of Lines Depending on the direction that lines are marked on the pavement, lines may be longitudinal, transverse, or oblique. And depending on the use and meaning of such lines, they are either broken or solid lines. A broken line shall consist of line segments of equal lengths separated by uniform gaps. The speed of vehicles on the section of road or in the area in question should be taken into account in determining the lengths of the strokes and of the gaps between them. A solid unbroken line is used where crossing of the line is either discouraged or prohibited. It is generally used to replaced or supplement a broken line where required, e.g., barrier lines, center lines, etc. solid lines may be either yellow or white, depending whether crossing the line is legally prohibited or not. 2.6.8 Width of Lines The width of solid or broken lines varies from 100 mm to 300 mm, depending on the usage of the specified line. Transverse lines are usually wider because of the angle at which the driver sees markings on the carriageway. 2.6.9 Messages Messages when used should be limited to as few words as possible, never more than three. They shall only be used to supplement other traffic control devices. The distance between words is variable, depending on the message and location at which it is based. (Usually twice the length of the word if achievable). The first word of the message is to be nearest the motorist on rural roads. In urban lowspeed areas, the order is optional. Messages are white in color. Letters or numerals used in roads in urban areas shall measure at least 2.5 m; on high-speed highways, they may need to be at least 5 m. Messages generally in use are STOP, KEEP CLEAR, SCHOOL, PED XING, RAILROD XING, SIGNAL AHEAD, NO RIGHT (LEFT) TURN, BUS LANE, and PUJ LANE.

2.6.10 Symbols a. Give way (yield) symbol The symbol used to supplement the give way sign consist of an isosceles triangle having two equal sides of 3.1 m and a base of 1 m. Outline width is 450 mm at the base and 150 m for the sides. The distance of the symbol from the holding line is between 5 m and 25 m, depending on the location and vehicle speeds on the road. b. Pavement arrows Pavement arrows are used for lane use control. White in color, they are generally 5 m in length on urban roads and 7.5 m on high-speed roads. For half-turn movements, the stems of the straight arrows can be bent to suit the particular direction of movement. The first set of arrows should be placed at a distance of 15 m from the stop bar, and the subsequent sets should be placed at 45 m apart. c. Numerals The only numerals that should be used are those associated with speed limits at location to supplement speed limit signs, which are continuously disregarded by drivers. 2.7 OBJECT MARKINGS AND MARKERS 2.7.1 Object Markings Physical obstruction in or near a roadway that constitute serious traffic hazard, including installations designed for the control traffic, shall be adequately marked typical obstructions of this character are bridge supports, monuments, traffic islands, beacons, signal and sign support, loading islands, railroads and draw-bridge gates, post of narrow rocks, and structures giving restricted and overhead clearance. For additional emphasis it is also advisable to mark obstructions rather than islands with reflectorized white paint with not less than five alternating black and reflectorized white stripes. The stripes shall slope downward at an angle of 45 degrees toward the side of the obstructions, and shall be uniform and not less than 100 m in width. A large surface, such as a big pier, may require stripes of 300 mm (see figure 2.3).

Figure 2.3 Object markings (Courtesy of R. Rellosa of 3M Phil)

In addition to the marking on the face of an obstruction in the roadway, warning of approach to the hazard shall be given by line markings on the pavement. Reflectorized yellow should be used on curbs of all islands located in the line of traffic flows especially on curbs directly ahead of traffic at T and offset intersections. 2.7.2 Raised Pavement Markers Raised pavement markers are small rectangular or dome-shaped devices that are fixed to the pavement surface to simulate or supplement painted pavement markings (figure 2.4). The markers can be reflective or nonreflective.

Figure 2.4 Raised pavement markers (The one on the right has built-in lightning.) (Left photo courtesy of R. Rellosa of 3M Phil.; right photo courtesy of Solamarkers Inc.) Raised pavement markers are generally not obscured at night and under wet conditions. The reflective type are more brilliant than reflectorized paint markings. Because of the high cost of installation and maintenance, use of raised pavement markings may be considered only in accident prone areas, e.g., on hilly areas where there is frequent fog and rain,. Figure 2.5 shows the visual effect of raised pavement markers.

Figure 2.5 Visual effect of raised pavement markers in between reflectorized pavement markings

Hazard markers Hazard markers are rectangular and generally consist of a series of alternating black and white bands (figure 2.6). The white portion is always reflectorized, but the reflectorized material may cover only the central portion of each white band in order to achieve a balance between the areas of black and white under headlight illumination. The bands may consist of either diagonal strips where only a target is required, or of chevrons where directional as well as target properties are desirable. Delineators Delineators are small reflective panels or button mounted on guide posts or guard fences as an effective aid for night driving (figure 2.7). Delineators are made of reflective material capable of reflecting light clearly visible under normal atmospheric condition from a distance of 300-500 m when illuminated by the upper beam of a standard automobile head lamp. Placement of delineators at the roadside of a circular curve is shown in figure 2.8.

Figure 2.6 Chevron markers (Photo courtesy of R. Rellosa of 3M Phil.)

Figure 2.8 Placement of permanent delineators along a roadway

Problems 1. Drive along Epifanio de los Santos Avenue (EDSA) or along any major roads in your locality. Note if traffic sign are visible or if they are obscured because of too many advertisement or billboard signs. Must there be regulations on putting up advertisement signs? 2. Nowadays, many local government units have been able to get support from private companies in fabricating and installing traffic signs at location under their jurisdiction, provided that the company’s logo or identification is indicated in a certain area of the sign (one-eighth to one-fifth of the total surface area). Would you agree to this? Why or why not? 3. In the town or city you are residing, identify the different traffic signs and see if they conform to the Vienna Convention as to color or shape. Would you agree if the signs do not conform to the national standards because they were fabricated at lower cost in your locality? 4. Most international signs consist mainly of symbols with minimum or almost no words in them. Would you suggest putting words in Tagalog or in any dialects in order to convey their meaning? Why or why not?

REFERENCES Department of Public Works and Highways (DPWH). 2004. Highway safety design standards. Road Safety Design Manual. Manila: DPWH. Planning and Project Development Office, Ministry of Public Highways. 1980 Manual on pavement markings. Federal Highway Administration (FHWA), US Dept. of Transportation. 1988. Manual on uniform traffic control devices for streets and highways (MUTCD). Santiago, Mariano R. ed. 1980. A compilation of edicts related to the land transportation system of the Philippines. Quezon City: Bureau of Land Transportation.