Code of Practice for Road Signs (Third Revision)

The scope of IRC 67 covers comprehensive specifications and standards for road signs including their classification, siting, orientation, materials, colors, sizes, visibility, and maintenance. Key specifications include:

• Material Specifications: Aluminum Composite Material (ACM) thicknesses of 3 mm and 4 mm with mechanical and aluminum skin properties as per Table 6.1 (Clause 6.1). For example, 4 mm ACM requires a minimum tensile strength of 40 N/mm² and peel off strength of 4 N/mm.

• Retro-reflective Sheeting: Minimum coefficients of retro-reflection for Type IX and Type XI prismatic grade sheeting are specified in Tables 6.8 and 6.9 (Clause 6.8 and 6.9) respectively, with values varying by color and observation angles.

• Sign Sizes and Letter Sizes: Detailed in Clauses 21 and 24 onwards, covering mandatory, cautionary, informatory, and other sign types.

This standard ensures uniformity and safety in road signage across Indian roads.

Sources: Clause 6.1, Clause 6.8, Clause 6.9, Preamble Table

For Layouts of Map Type Advance Direction Signs (ADS) as per IRC 67:

• Route Symbol Width:
  • NH, SH, Urban roads: 6 s/w
  • MDR: 4 s/w
  • Village roads: 2.5 s/w
• Route Symbol Tips: Chamfered at 60°
• Side Turning Symbol: Extended 2/3rd distance from forward symbol to border
• Destination Names: Stacked with aligned initial letters (English & Hindi)
• Forward Destination: Centered on forward route symbol; displaced right/left if only one side turning
• Back & Side Destinations: Below route symbol, 18 s/w from forward destination
• Spacing: Minimum 4 s/w lateral and 3 s/w vertical between route symbol and place names
• Forward Symbol Size: Minimum 12 s/w; bottom 1.5 s/w from bottom border
• Font Height: From Table 11.1 (speed-based)

For roundabouts:

• Roundabout symbol outer radius 12 s/w, inner radius 7 s/w, concentric circles discontinued
• Minimum 2.5 s/w vertical spacing between route symbol and place name
• Place names placed so imaginary tile touches circle of radius 2 s/w beyond outer circle

Stroke width (s) = 1/4 of lower case "x" height; letters placed in imaginary tile 2x "x" height = 8 s/w height.

These details are illustrated in Figs. 16.01 and 16.02.

This ensures clarity, uniformity, and legibility of map type ADS per IRC 67.

Sources: Clause 11.1, Clause 16.01, Clause 16.3.2.1

For Layouts of Flag Type Direction Signs (Fig. 16.04) as per IRC 67:

• The appropriate end of the sign plate shall be chamfered at 120°, with the pointed end reduced by 1 s/w (stroke width).
• The chevron is placed 3½ s/w from the end border and 1½ s/w from the top and bottom edges.
• Place names are separated by 1½ s/w from the chevron.
• Chevron widths vary with lines of information:
  • 4 s/w for 2 lines,
  • 3½ s/w for 1 line,
  • 4½ s/w for 3 lines,
  • 5 s/w for 4 lines.
• Font height for different speeds is taken from Table 11.1 (Columns 7 & 8).

Additional common principles:

• Stroke width (s/w) is ¼ of the lower case "x" height.
• Letters are placed in an imaginary tile of 2x height (8 s/w height).
• Borders are 1½ s/w wide with internal corner radii of 2 s/w (outer) and 1 s/w (inner).

These specifications ensure clarity and uniformity in flag type direction signs as per IRC 67 Clause 16.04 and Clause 11.1.

Sources: Clause 16.04, Clause 11.1

For Layouts of Reassurance Signs (Fig. 16.05) as per IRC 67 Clause 7 and Clause 11.1:

• Kilometrage shall be centered over place names and route numbers if used.
• Place names shall be left aligned.
• Kilometrage shall follow the related place name on the same line, aligned right, with a minimum spacing of 3 stroke widths (s/w) from the longest place name.
• The farthest destination is placed on the top panel, nearest on the bottom panel.
• Font height for different speeds shall be taken from Table 11.1 (Columns 7 & 8).

Additional general layout rules from Clause 16.01:

• Stroke width (s) is 1/4 of the lower case "x" height.
• Letters are placed in an imaginary tile of 2 times "x" height (8 s/w height).
• Related words on the same line are separated by 1.5 s/w.
• Borders are 1.5 s/w wide with internal corner radii of 2 s/w (outer) and 1 s/w (inner).

These specifications ensure clarity and uniformity in reassurance sign layouts.

Sources: Clause 7, Clause 11.1, Clause 16.01

For Layouts of Place Identification Signs as per IRC 67, Clause 16.06 and related clauses:

• The lines of legend shall be centered one over the other.
• The font height for different speeds shall be taken from Table 11.1 (Columns 7 & 8) as per Clause 11.1.
• Stroke width (s) is 1/4 of the lower case "x" height, and letters are placed in an imaginary tile of 2x height (8 s/w height) as per Clause 16.01.
• Related words on the same line are separated by 1.5 s/w; borders are 1.5 s/w wide with internal corner radii of 2 s/w (outer) and 1 s/w (inner).
• Borders are separated from the top and sides of the imaginary tile by 2.5 s/w and from the bottom by 1.5 s/w.

These specifications ensure uniformity and legibility of place identification signs on roads.

Sources: Clause 16.06, Clause 11.1, Clause 16.01

As per IRC 67 Clause 2.4, maintenance of road signs involves ensuring their legibility and visibility at all times. This includes regular functional evaluations at periodic intervals to assess if signs need replacement or updating to suit current traffic conditions. Cleanliness, clear lettering, and proper mounting are essential to maintain effectiveness and command respect from road users. While no specific formulas or tables are provided in the retrieved context for maintenance, the emphasis is on periodic inspection and upkeep to retain sign functionality.

Sources: Clause 2.4

According to IRC 67, regulatory signs are circular with a red border, white background, and black symbols (Clauses 14.3 and 14.4). The sizes and dimensions for mandatory and regulatory signs are specified in Tables 14.3 and 14.4 (not fully reproduced here). For 'STOP' signs, Table 14.1 provides sizes based on approach speed on the minor road:

For cautionary signs, Table 15.1 specifies sizes, border widths, clear visibility distances, and siting distances based on design speed:

These tables guide the selection of sign size, shape, and color for effective visibility and compliance.

Sources: Clause 14.1, Clause 14.3, Clause 14.4, Clause 15.1

As per IRC 67, Clause 15.1 and Table 15.1, cautionary signs have specified sizes, border widths, clear visibility distances, and siting distances based on design speed. The key parameters are:

These distances ensure adequate driver reaction time and visibility. Installation warrants must follow these siting distances based on design speed and visibility as per Clauses 21.4 and 22.4 referencing Table 11.1 for regulatory and warning signs.

This ensures safety by placing signs at appropriate distances ahead of hazards for the given speed.

Sources: Clause 15.1, Table 15.1, Clause 21.4, Clause 22.4

For Direction and Place Identification Signs as per IRC 67, key specifications include:

• Font Height: Determined by vehicle speed from Table 11.1 (referenced in Clauses 11.1, 4, 5, 6, 7, 8).

• Route Symbol Widths:

  • NH, SH, Urban roads: 6 s/w
  • MDR: 4 s/w
  • Village roads: 2.5 s/w (Clauses 4 and 5)

• Chamfering: Route symbol tips chamfered at 60°; flag type sign ends chamfered at 120° (Clauses 4, 6).

• Layout Rules:

  • Side turning symbols extend 2/3 distance from forward symbol to border.
  • Multiple destinations stacked with aligned initials (English and Hindi).
  • Forward destination centered or displaced for one side turning.
  • Minimum spacing: 4 s/w laterally, 3 s/w vertically between symbols and place names.
  • Forward symbol minimum 12 s/w; bottom 1.5 s/w from border. (Clauses 4, 5)

• Roundabout Signs: Outer radius 12 s/w, inner radius 7 s/w, concentric circles discontinued (Clause 5).

• Reassurance and Place Identification Signs: Legend lines centered; kilometrage aligned right with minimum 3 s/w gap (Clauses 7, 8).

• Sign Placement Heights: From Table 4.1 (Clause 4.1), e.g., minimum 600 mm to maximum 9000 mm depending on sign type.

These details ensure legibility and uniformity in sign design and placement.

Sources: Clause 11.1, Clause 4.1, Clause 4, Clause 5, Clause 6, Clause 7, Clause 8

IRC 67 provides specifications for Facility and Other Useful Information Signs primarily in Clause 16.17, which includes Fig. 16.17 showing definitions and supplementary plates. These signs are designed to convey essential information to road users clearly and effectively. Key aspects include:

• Design and Layout: Signs should have clear symbols and text for easy recognition.
• Supplementary Plates: Used to provide additional information or clarify the main sign.
• Dimensions and Colors: Follow standard sizes and color codes for visibility and consistency.

Unfortunately, the exact formulas, tables, or detailed specifications for these signs are not provided in the retrieved context. For precise dimensions, color codes, and placement guidelines, refer directly to IRC 67 Clause 16.17 and associated figures.

If you need detailed tables or formulas, please provide the specific clause or section.

Sources: Clause 16.17, Fig. 16.17

As per Clause 22.7 and Clause 21.7, the size of letters on traffic signs shall follow Table 11.1, which relates letter x-height to design speed and sign type for legibility. Supplementary plates attached to facility, regulatory, or cautionary signs should have letters of 100 mm size, with 100-125 mm recommended for timing information like "09:00 am to 08:00 pm". According to Clause 11.1, letter size (x-height) depends on road speed and classification to ensure adequate legibility without being obtrusive. Table 11.1 specifies letter sizes and minimum clear visibility distances for various sign types (advance direction, flag type, reassurance, place identification) for both shoulder and gantry mounted signs. The table also notes minimum values in brackets for constrained sites and typical distances for advance direction signs at grade-separated junctions (250-750 m and 750-1500 m).

Sources: Clause 22.7, Clause 21.7, Clause 11.1, Table 11.1

IRC 67 provides detailed sign plan examples for typical road situations in Annexure V (Figures V.1 to V.10), covering junctions, roundabouts, flyover approaches, curve delineation, cloverleaf interchanges, and rest areas. These plans are indicative and must be adapted by engineers considering local conditions (Clause 23).

Key formulas for sign legibility include:

• Cut-off distance C = S × cot 10° = S × 5.7, where S is offset from driving lane center.
• Reading distance R = Reading time × Speed, with reading time = 2 + (N/3) seconds (N = number of words).

Tables VI.1 and VI.2 specify "x"-height of letters for shoulder and gantry mounted signs based on speed, lanes, and distances. For example, at 100 kmph on a 2-lane road, shoulder mounted signs require 273 mm uppercase "X" height, gantry mounted 312 mm (Tables VI.1 & VI.2).

Font heights for different speeds are given in Table 11.1 (Clause 11.1). Layouts for various sign types (map-type, flag-type, reassurance, place identification) are detailed with dimensions in Clauses 14.5 and 11.1.

These specifications ensure visibility and comprehension for drivers under typical Indian road conditions.

Sources: Clause 23, Table VI.1, Table VI.2, Clause 11.1, Clause 14.5