Code of Practi ce for Road Sign s IRC IRC 67-20 67-2001 01 Supplementary Supplementary Techni Techni cal Advic e 1. Introduction IRC 67-2001 is the official guide to designing, manufacturing and installing traffic signs in India. It is a good introduction to this complex complex subject, but there are some confusions, contradictions and omissions, which which this note seeks to resolve. It provides technical advice which supplements and in some cases modifies the guidance given in the the IRC Code. The note follows the layout of the IRC Code. 2. Classifi cation of Road Road Signs 3. Siting of Signs wit h Respect Respect to the Carriageway Carriageway Figure 1 illustrates the main requirements. Fig. 1 Heigh Heigh ts and Clearances
B A H D
D
No shoulder
Shoulder
C
E
C
Kerb
Footway
A B C D E F G H
G
D
F A
C
Kerb Minimum (mm) 600 1000 300 2000 2100 5500 750
Desirable (mm) 1000 2000 600 2000 2100 5900
Maximu Maximu m (mm) 2500 3000 1000 2500 2500
5000
Notes 1. Mandatory signs (e.g. Keep Left) on traffic islands are normally mounted so that the bottom edge is about 1000mm above the paved surface.
When several signs have to be placed along the same section of road take care that they do not obscure each other. Locate the signs a minimum of 0.6V metres apart (where V is the 85 percentile speed in km/h). Signs are normally erected on the left side of the road, but for extra emphasis a second sign may be placed on the right side of the road. This is especially useful on left-hand bends.
4. Orientation of the Signs Figure 2 illustrates how signs should be orientated. This helps to avoid glare from reflective signs at night. Fig. 2 Sign Orientation
95
o
5. Material for Signs It is not advisable to use concrete, because the resulting sign or sign support would be too heavy and rigid. Any vehicle hitting the sign would likely be severely damaged. Where concrete is used the sign should be shielded by a guardrail or crash barrier. Retro-reflective sheeting High Intensity Grade sheeting is recommended for most purposes. It is generally not worth using Engineer Grade because its performance is much lower than High Intensity and it is only slightly cheaper. Several manufacturers now produce a high-performance sheeting called variously, Microprismatic, Wide Angle Prismatic, Diamond Grade, or Type IX, but it is considerably more expensive than High Intensity Grade sheeting. It is appropriate for difficult situations, such as in town centres where street lights and illuminated advertising signs reduce the reflective brightness of the signs, or where the sign will be viewed from a wide angle. Sign specifications Specifications for all aspects of sign manufacture are set out in the Road Safety Cell’s “Special Specifications – 800 – Signs, Markings and Other Appurtenances.” This is a modified version of the MoST / MoRTH Specifications.
6. Posts and Mountings for Signs 7. Colour for Signs The IRC Code (para. 7.5) specifies that the colour of informatory (Route Information) signs shall be distinct for different classes of road. See Table 1 overleaf:
Table 1 Colour Code for Route Information Signs Sign group
Road type on which sign is positioned
Road type to whi ch sign refers
Advance Direction and Direction Signs
NH and SH roads
NH and SH roads
Other roads Reassurance Signs Place Identification Signs Temporary Diversion Signs
NH and SH roads NH and SH roads All roads
Other roads NH and SH Other roads NH and SH roads All roads
Colours of sign (lettering / background) White on green (see notes below) Black on white White on green Black on white White on green White on green Black on yellow
Notes 1. Where the sign gives information on NH or SH roads and other roads it will have white lettering on a green background throughout. 2. Signs on NH or SH roads through towns which refer exclusively to local in-town destinations will have black lettering and symbols on a white background.
8. Sizes of Sig ns 9. Visibility of Signs 10. Sizes of Letters The size of lettering on Route Information signs (the IRC Code refers to them as Direction and Place Identification signs) must be related to the speed of approaching traffic. Table 2 gives the details. It differentiates between: • • • •
Advance direction signs (ADS) (IRC Fig.15.1, 15.2 and 15.3) - placed before the junction Direction signs (IRC Fig. 15.4, 15.5) – placed at the junction and pointing in the appropriate direction Route confirmatory (Reassurance) signs (IRC Fig. 15.6) – placed after the junction Place identification signs (IRC Fig. 15.7) – placed at the entrance to a town or village
Refer to the Sign Layout section of this note for illustration of sign placing at junctions. Letter sizes are referred to in terms of “x” heights. This is the height of a lower-case “x” in the English (Latin) alphabet (see section titled “Annexure – 4 Rules for the Design of Informatory Signs” for more information). IRC para. 10.3 states that lettering on ADS on NH/SH should have an “x” height of at least 150mm, but it is recommended that the advice in Table 2 be used instead. References in the same paragraph to letter thickness and size of upper case initial letters are misleading and should be ignored. In the chosen letter style (Transport) the upper case letters (capitals) are always 1.4 times the “x” height.
Table 2 Size and Siting o f Route Inform ation Signs Advance Directi on Signs (ADS)
1 85th percentile approach speed of cars
2 “x” height (mm)
Up to 50 km/h 50 - 65 km/h 65 - 80 km/h 80 - 90 km/h Over 90 km/h
75 (60) 100 (75) 125 (100) 150 (125) 200 (150)
3 Minimum clear visibility to the sign (m) 45
4 ONE sign: distance from junction (m)
Direct ion Si gns Reassurance Signs Place Identification Signs
45
5 TWO signs: distance between 1st and 2nd sign (m) -
60
90
50
80
90 - 150
70
90
150 - 225
100
115
225 - 300
100
6 “x” height (mm)
60 (50) 75 (60) 100 (75) 125 (100) 150 (125)
7 Minimum clear visibility to the sign (m) 35 45 60 75 105
Notes th 1. The 85 percentile speed is the speed exceeded by only 15% of vehicles. 2. The “x” height is the height of a letter "x". Multiply the “x” height by 1.4 to get the equivalent height of a capital letter. 3. In the case of signs on roads with more than 2 lanes in the same direction use the next larger x-height. 4. In columns 2 and 6 the smaller “x” heights shown in brackets are the absolute minimum sizes to be used where site space is limited. 5. In columns 3 and 7 the clear visibility distances indicated are minimum values. Greater distances should be provided wherever possible. 6. Two advance direction signs can be used where there is too much information to put on one sign. Typically, the first sign will show primary destinations; the second sign will show local destinations and will be closer to the junction. The distance between the two signs is indicated in column 5. So, where the approach speed is 60 km/h, the first sign will be 140m in advance of the junction and the second sign will be 90m in advance of it. 7. Reassurance Signs are normally placed about 100-150m after the junction. Place Identification Signs are normally placed about 90m in advance of the start of the built-up area.
11. Maint enance of Signs 12. Defin iti on Plates / Suppl ementary Plates Table 3 Suppl ementary Plates – Letter Size Letter height (capital letters) (mm) 100 125 150
Warning signs length of side (mm) 700 900 1000
Regulatory si gns diameter (mm) ≤600
750 900
The IRC Code section 12. states that the border of supplementary plates shall be 20mm wide, but this contradicts Annexure 4, section H which states that the border shall be 1 stroke width. The latter is correct. See comments on Annexure 4 for further explanation.
13. Mandator y / Regul atory Signs Table 4 Size of Mandatory / Regulator y Signs Site type Signs attached to traffic signal heads Sites where space is limited (e.g. on narrow traffic islands) Traffic speeds up to 50 km/h Traffic speeds between 50 km/h and 65 km/h – STANDARD SIZE Traffic speeds above 65 km/h Sites where additional emphasis is required – because of a bad accident record
Diameter of sig n (mm) 300 450 600 750 900 900
Mandatory / regulatory signs are normally sited at or near the point where the instruction applies.
No Entry signs (Fig. 13.3) It is recommended that these be a minimum of 750mm diameter, and be installed in pairs (lefthand side and right-hand sides of the road). Speed Limit signs (Fig. 13.22) It is recommended that these signs be installed in pairs (left-hand side and right-hand sides of the road) for maximum visual impact. They may also be mounted on yellow backing boards. The speed limit should be one of the following: 30, 40, 50, 60.
14. Cauti onary / Warni ng Signs Table 5 Size and Siting of Cautio nary / Warning Signs Site type
Traffic speeds up to 50 km/h Traffic speeds between 50 km/h and 65 km/h – STANDARD SIZE Traffic speeds above 65 km/h Sites where additional emphasis is required – because of very high speeds and / or a bad accident record
Length of triangle side (mm) 700 900 1000 1340
Distance of sign from hazard (m) 45 90 120 200
Sharp Bend / Curve Signs (Fig. 14.1) The advice given in IRC para.14.4.1 on where to use this sign goes against international signing practice and should be ignored. The Vienna Convention on Road Signs and Signals specifies that this sign should be used to warn of dangerous bends, and the usual definition of this is: “a bend in the road which is difficult to negotiate without slowing down significantly, and the severity of which cannot easily be seen”. It cannot be defined by reference to curve radius alone. Changes in alignment that are not hazardous should be signed with roadside delineator posts.
Non-IRC Warning Signs The following signs are recommended for use, although they are not included in the IRC Code.
Height Limit Ahead (Fig. K2.1) This provides advance warning of a height restriction, such as might be caused by a low bridge.
Accident Blackspot Sign (Fig K2.2) This sign is used to warn of a serious accident blackspot.
Dangerous Obstruction Sign (Pass either side) (Fig. K2.6) This sign is used to warn of an obstruction which can be passed on either side – such as the nose at the start of an exit lane off an expressway. The sign has yellow chevrons on a black background.
Sharp Change of Direction at T-junction Signs (Fig. K2.7) This sign is used at T-junctions to tell traffic approaching on the minor road that it must turn left or right. The sign has yellow chevrons on a black background. See the Sign Layouts section for an illustration of where it is used.
Dangerous Obstruction Sign (Pass one side) (Fig. K2.9) These signs are used to warn of hazardous obstructions close to the edge of the lane, such as bridge parapets. There is one for the left-hand side and one for the right-hand side. The sign has yellow diagonal bars on a black background.
Sharp Change of Direction Chevron Signs (Fig. K2.8) This sign is mostly used at dangerously sharp bends, especiall y those where the sharpness is difficult to see in advance. Although becoming widely used in India it does not appear in the IRC Code of Practice. There are three types – see Fig. 3 overleaf. The single chevron sign is for placing at intervals around the outer edge of large radius curves. It is also useful where there is only sufficient space for a small sign, such as in cuttings or on embankments. The other two
signs (with multiple chevrons) are for use at sharp radius curves – they have more visual impact than the single chevron sign. The two-chevron sign is also used on the centre island of roundabouts to indicate that drivers must turn sharply left on entering the circulatory carriageway (see the Sign Layouts section). Signs K2.8A and K2.8B have yellow chevrons on a black background. Sign K2.8C has a black chevron on a yellow background. Fig. 3 Positioni ng of Chevron Signs
K2.8A K2.8C
K2.8B
15. Informatory Signs Section 15.3 of the IRC Code sets out the requirements for the design of Route Information signs, but note: Signs will have green backgrounds only if they refer to NH or SH – for other roads the • background will be white; Including distances and route numbers on Advance Direction Signs and Direction Signs is • not recommended, because it will make the signs too big and expensive;
• •
At a junction the Direction Signs and the Reassurance Signs, if any, must repeat the place names given on the Advance Direction Signs; The place names on Reassurance Signs shall be listed in order of distance (furthest at the top) not population size.
Care is needed when selecting the place names to put on signs. It is important to be consistent at each junction along a route. In other words, once a place name appears on a sign it must appear on every subsequent sign until that place is reached. Major places that are near to the route, but not on it, can be shown on the sign. At major junctions on National Highways the signs will normally refer only to the more important places, such as Alappuzha, Ernakulam, Kannur, Kasargod, Kochi, Kollam, Kottayam, Kozhikode, Malappuram, Palakkad, Thiruvananthapuram and Thrissur. Reassurance Signs may show the destination at the end of the route (e.g., Salem and Kanyakumari on NH47). When considering the provision of Facility Information Signs it is recommended that priority be given to signs showing the location of Hospitals, First Aid Posts, and Police Stations.
16. Backing Boards Signs can be mounted on yellow or grey backing boards to make them more prominent. This is useful where there is a distracting background or the sign is particularly important. Yellow backing boards are very effective but should only be used for critical signs – if they are too widely used drivers will stop noticing them. Signs assemblies (two signs, or a sign and a supplementary plate) will often look neater, and be much stronger, if they are combined on a single plate. Fig. 4 Mounting of Signs on Backing Boards
An nexur e 4 Rul es f or th e Design of Inf or mat or y Ro ad Si gn s Alphabets The alphabets (fonts) to be used on traffic signs are: Transport Medium – for white letters (English) on green, or blue backgrounds Transport Heavy (Bold) – for black letters (English) on white or yellow backgrounds Shree502 – for white or black letters (Malayalam).
The Transport lettering has been specially developed for traffic signs. Transport Medium has thin strokes so as to counteract the effect of the overglow of white reflective material against a darker background. Transport Bold is always used for black letters on white, so that the overglow of the white background does not obscure the letters. All three styles are available as Windows TrueType fonts for those wishing to design route signs on computer. Never condense the lettering or reduce the letter spacing in order to squeeze the words into the available space, as this will greatly reduce its legibility, especially at night. Capital letters (English) are 1.4 times the “x” height. The rules for designing sign layouts are specified in stroke widths. 1 stroke width (s/w) is one quarter the “x” height. To ensure correct spacing when forming a word, the letters in each alphabet are placed on imaginary tiles - see Fig. 5 below. The tiles vary in width, but have a fixed height which ensures correct line spacing. Designing signs on computer using Autocad or other drawing software means that letter spacing and line spacing is taken care of for you. Fig. 5 Tiles and letters
0.4 s/w 5.6 s/w 2 s/w
X
2 s/w 1.4x
8 s/w 2.0x
4 s/w
1.0x
2s/w Imaginary Text Tile
The IRC Code (page 28) Table 4(a) contains a “Remarks” section which sets out letter heights and stroke widths for various types of signs. It is recommended that the advice given in Table 2 of this note (where letter height is related to traffic speed) be used instead. Layout of Signs A. General Route Information signs are not standard sizes. Never try and squeeze words onto a sign plate of a specific size. You must first determine the size of the lettering to be used, which has to be large enough for drivers to read at a distance. Refer to Table 2 in this note for the letter sizes for informatory signs. The letter size that you select, (more specifically, the “x height”) is critical to the design, because the design rules specify dimensions in terms of stroke widths – and a stroke width is always one quarter of the “x” height. The design rules common to all Route Information signs are as follows (although there are a few exceptions): Make the sign as small as the design rules allow •
• • • • • •
Place names are to be given in Malayalam and English – with the Malayalam word stacked above the other and with their initial letters aligned (i.e. ranged left) No more than four destinations (place names) are permitted on one sign No more than two destinations are permitted for any one direction (except for Reassurance Signs) Where two destinations are shown for one direction the nearer of the two shall be stacked above the other and with their initial letters aligned All the lettering on the sign shall be the same size regardless of the importance of the destination Corners of the signs are to be rounded for greater safety and better appearance.
Figure 6. shows the basic layout for a simple sign. Fig. 6 Basic Layout
2.5 s/w 1.5 s/w
2.5 s/w 8 s/w
Place names stacked with their initial letters aligned - Malayalam name above English name
8 s/w 1.5 s/w
Radius of 2 s/w on internal corners 2.5 s/w B. Letter and word spacing C. Map-type advance direction signs (other than for roundabouts) Map-type ADS give the clearest information on the layout of the junction ahead, but they are big and expensive, so they should only be used at complex junctions. The actual layout of the junction shall be shown in diagrammatic form, but the route symbol representing the approach road shall always be vertical. Where the junction is on a bend there should be a vertical section (6 s/w in length) before the route symbol starts to curve. Figure 7 illustrates the layout principles. It shows a junction with a simple layout, for ease of illustration. A stack-type sign would be just as acceptable here, and would be more economic. The IRC Code (page 33) C.(iv) (e) specifies 1.5 s/w between route symbols and the place names below. This needs to be increased to 2.5 s/w in order to keep sufficient separation between the route symbol arrowhead and the lettering.
Fig. 7 Layout of Map-Type ADS
1.66 SW 1 SW
0
60
min. 12.5 s/w
L 2/3 L 4 s/w (DR)
radius 1 s/w
symbol width (SW)
2.5 s/w
1.5 s/w 4 s/w 6 s/w (NH or SH)
2.5 s/w
D. Map-type advance direction signs for roundabouts Roundabouts should always have map-type ADS. Figure 8 illustrates the layout principles. The actual layout of the junction shall be shown in diagrammatic form, but the route symbol representing the approach road shall always be vertical. Where the junction is on a bend there should be a vertical section (6 s/w in length) before the route symbol starts to curve. The IRC Code (page 33) D.(i) specifies the length of entry arm as either 22 or 30 s/w, but it is recommended that this be ignored as it would make the sign unnecessarily large. Fig. 8 Layout of Map-Type ADS for Roundabouts 12 s/w
12 s/w min. (all exit arms) 12 s/w 7 s/w 14 s/w 30
o
E. Stack-type signs Figure 9 illustrates the layout principles. Arrows may be vertical or horizontal or at any angle in 0 between in increments of 22.5 . The IRC Code (page 33) E.(iii) specifies that black borders on local advance direction signs shall be 4 s/w wide, but this will make the border too prominent, so it is recommended that the standard width of 1.5 s/w be used. Fig. 9 Layout of Stack-Type ADS
F. Direction signs Figure 10 illustrates the layout principles. Fig. 10 Layout of Direction Signs
3.5 s/w
W
0
60
Width of chevron (W): 1 line of text = 3.5 s/w 2 lines of text = 4 s/w 3 lines of text = 4.5 s/w 4 lines of text = 5 s/w
0
120
radius 1 s/w
1.5 s/w radius 3 s/w
1.5 s/w
G. Route confirmatory (Reassurance) signs Figure 11 illustrates the layout principles. Fig. 11 Layout of Route Confirmator y (Reassurance) Signs
equal equal
2.5 s/w
2.5 s/w
Borders are to be designed as on stack-type signs.
H. Supplementary Plates Figure 12 illustrates the layout principles. Fig. 12 Layout of Supplement ary Plates 1 s/w
2.5 s/w
1.5 s/w Radius of 1 s/w on internal corners
2.5 s/w
Supplementary plates always have black lettering and border on a white background. The English legend is always in capital letters. Note that unlike other signs the border is only 1 s/w wide. I. Table of measurements of stroke widths Stroke widths are one quarter of the “x” height. If you follow this rule exactly you may find that you are using dimensions expressed in parts of a millimetre, in which case you can, if you wish, round them up or down to the nearest millimetre. The Table in Section I of the IRC Code gives you alternative dimensions, which, if used, will avoid the need for rounding. In practice, it will not matter which method you use.
Incorporating Warning and Regulatory Signs within Route Information Signs Where there is a significant hazard or restriction on one of the routes shown on a sign it is helpful to drivers to warn them, as this may influence their choice of route. This can be done by incorporating the appropriate regulatory / warning sign in the design. Figure 13. illustrates how this should be done. Fig. 13 Regulatory and Warning Signs w ithin Route Information Signs (A) on map-type signs
24s/w
24 s/w
1.5 x the width of the route symbol
1.5 s/w
1.5 x the width of the route symbol
1.5 s/w
(B) on stack-type signs
24 s/w
2.5 s/w
24 s/w
2.5 s/w
2.5 s/w
2.5 s/w
Symbols on Route Information Signs Symbols may be used on route signs to help road users make the correct route choice. The most common example is the aircraft symbol used to denote an airport (see Figure 14 below). On route signs with a green background a white symbol will be used; on other signs the symbol will be black. The aircraft (airport) symbol is normally positioned to the right of the airport name or the name of the place where the airport is located. It can also be used on its own. The aircraft generally points in the same direction as the route symbol, arrow, or chevron, except that it never points below the horizontal. The height and width of the symbol shall be equal to 10 s/w. Fig. 14 Airpo rt symbo l 10 s/w
10 s/w
Overhead Route Information Signs Overhead (gantry-mounted) signs can be useful on roads with two or more lanes in the same direction. Advertising companies offer to erect overhead traffic signs in return for being allowed to include advertising, but the signs they put up are usually poorly-designed and have no value as traffic signs. In future, advertising companies must only be allowed to erect overhead signs when the following conditions are met: 1. there is a real need for a sign at the proposed location; 2. the route information part of the sign is designed / approved by PWD and is in accordance with the rules set out in IRC-67-2001 and this document (the PWD Road Safety Cell can advise); 3. the advertising appears on a separate panel above the route information sign (not below it) and does not divert attention from the route information; 4. the sign is manufactured using microprismatic grade reflective sheeting to specifications set by PWD; 5. the sign supports do not encroach into the carriageway and the clearances set out in Figure 1 in this document are respected. Overhead signs are in a poor viewing position relative to side-mounted signs, so the letter size has to be much larger to compensate. The IRC Code (page 7) para. 10.3 states that the “x” th height on overhead signs shall be 300mm, but 200mm will normally be adequate where 85 percentile speeds are ≤ 80 km/h. Layouts for overhead signs may vary to suit the particular requirements at the site. Figures 15 and 16 show two different types.
Fig. 15 Overhead-mount ed Adv ance Directi on Sign A Ë o Ls M > Angamali
SWL· p U k Oj s P¡
> Kottayam
Punalur
>
Note: this is an advance direction sign on a dual 2-lane primary road ahead of a junction where there is a left slip road leading to Angamali. Note that there is no route information above the right-hand carriageway.
Fig. 16 Dedicated Lane Adv ance Directi on Sign (overhead mou nted)
Note: this is an advance direction sign on a 3-lane road. Lanes 1 and 2 can be used by traffic heading for East Fort and Vallakadavu. Lane 3 is only for traffic that will turn right at the junction to go to Kovalam.
