IRC Code 67: Material and Design Specifications for Road Signs - Ensuring Durability and Visibility

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Road signs are a fundamental part of traffic regulation and road safety. In India, their design and application are governed by the IRC Code 67-2012 — Code of Practice for Road Signs. This standard, developed by the Indian Roads Congress (IRC), aligns with global frameworks like the Vienna Convention on Road Signs and Signals (1968). It ensures uniformity, clarity, and effectiveness in guiding road users.

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In this blog, we dive deep into the material and design specifications outlined in IRC Code 67, emphasizing how these standards ensure durability and visibility on Indian roads.

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Purpose of IRC Code 67

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The primary objectives of this code are:

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• To provide a uniform system of road signage across India.

• To enhance road safety through clear, legible, and strategically placed signs.

• To ensure that signs are durable under Indian climatic and traffic conditions.

• To offer specifications for design, placement, and materials used in road signs.

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Classification of Road Signs

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As per IRC Code 67, road signs are categorized into three main types:

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1. Mandatory/Regulatory Signs: Indicate legal obligations. Example: Stop, No Parking.
2. Cautionary/Warning Signs: Alert road users to potential hazards. Example: School Ahead, Curve Ahead.
3. Informatory/Guide Signs: Provide useful route or facility-related information. Example: Distance Markers, Fuel Stations.

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Each category follows specific design rules for shape, color, and size.

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Material Specifications for Road Signs

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Durability and visibility start with the right materials. IRC Code 67 outlines rigorous material standards to ensure long-term performance:

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1. Substrate Materials

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• Aluminum Sheets: Must conform to IS 736, known for corrosion resistance.

• Aluminum Composite Material (ACM): A sandwich structure with LDPE core, offering excellent rigidity and resistance to warping.

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2. Retro Reflective Sheeting

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Used to enhance nighttime visibility, reflective sheeting is divided into:

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• Class A: Engineering Grade (Type I & II)

• Class B: High Intensity Prismatic (Type III & IV)

• Class C: Micro Prismatic (Type VIII, IX, XI)

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Each class offers different levels of retro-reflectivity, durability, and weather resistance. Class C is recommended for high-speed roads and gantry-mounted signs.

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3. Support Structures

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• Posts made from GI pipes (IS 1239), Square/Rectangular Hollow Sections (IS 4923, IS 3589).

• Foundations are designed for storm wind resistance and vandalism protection.

• Epoxy coating and anti-rust treatments are mandatory for posts and mounting hardware.

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Design and Dimension Specifications

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1. Shape and Color Coding

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• Mandatory signs: Circular, red border, white background.

• Warning signs: Triangular, red border, white background.

• Informational signs: Rectangular, blue or green background based on road type.

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2. Size and Lettering

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• Letter sizes are based on road type and design speed.

• “x-height” is standardized, ensuring legibility at varying speeds.

• Use of “Transport Medium” font is mandatory for consistency.

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3. Color Chromaticity and Luminance

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Colors must conform to ASTM D4956 standards for day and night visibility. This includes chromaticity coordinates and luminance values for each color, ensuring uniform recognition across all road users.

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Placement and Orientation of Signs

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Proper siting ensures visibility and readability:

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• Signs should be placed on the left-hand side, with additional signs on the right for multi-lane roads or curves.

• Ground-mounted signs must be 600 mm to 3 meters from the edge of the pavement.

• Overhead signs require a minimum clearance of 5.5 meters above the roadway.

• Signs on kerbed roads should maintain a minimum height of 2.1 meters.

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Orientation Tips:

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• Installed at right angles to the direction of travel.

• In curves or reflective glare zones, signs should be slightly tilted for optimal visibility.

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Maintenance Guidelines

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Long-term durability is only ensured through periodic maintenance:

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• Biannual inspections: Day, night, and during rainfall.

• Cleaning: Regular removal of dust, algae, and grime.

• Repainting: Every 2 years for signposts.

• Replacement: End-of-life or faded reflective sheeting must be promptly replaced.

• Labeling: Installation date and reference number must be stamped on the rear.

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Supplementary/Definition Plates

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When needed, signs may be supplemented with definition plates (e.g., "For Trucks Only", "8 AM - 8 PM"). These must follow retro-reflective standards and use a white background with black letters.

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Why IRC Code 67 Matters

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• Uniformity: Consistency across the nation simplifies road use.

• Legal Enforceability: As per the Motor Vehicles Act, signs complying with IRC standards have legal validity.

• Enhanced Road Safety: Reduces confusion and increases driver response time.

• Global Alignment: Harmonized with international standards like the UN Protocol and Vienna Convention.

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Conclusion

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IRC Code 67 is the cornerstone for effective road signage in India. From materials and mounting to reflectivity and maintenance, the code ensures road signs are built to last and perform under diverse conditions. For road engineers, contractors, urban planners, and safety auditors, understanding and applying IRC 67 is critical for building safer and more navigable roads.

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