Understanding IRC: 7-2017 - Recommended Practice for Numbering Culverts, Bridges, and Tunnels

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The Indian Roads Congress (IRC) has established a comprehensive framework for the numbering of culverts, bridges, and tunnels through its document IRC: 7-2017. This recommended practice aims to enhance asset management and facilitate the identification, inspection, and maintenance of road structures across the country.

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Background

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The original document, IRC: 7-1971, was first published in 1959 and revised in 1971. Recognizing the need for an updated approach, the General Design Features (Bridges & Grade Separated Structures) Committee (B-1) initiated a revision process. The draft was approved in January 2016 and subsequently endorsed by the Bridges Specifications & Standards Committee (BSS) in June 2017. The final approval was granted by the IRC Council during its 212th meeting in July 2017, after considering feedback from various members.

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Importance of a Uniform Numbering System

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A standardized numbering system for all road structures is crucial for effective asset management. It allows for easy identification of the location and type of structures, which is essential for personnel involved in inspection and maintenance. The document covers a wide range of structures, including:

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• Culverts (slab, box, hume pipes, etc.)
• Bridges (minor and major)
• Underpasses and overpasses
• Flyovers and grade separators
• Tunnels
• Any other relevant structures

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Numbering Conventions

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Serial Numbering

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All structures on a road are to be numbered in a serial order, with each kilometer treated separately. The numbering format is a fraction, where the numerator indicates the kilometer and the denominator represents the serial number of the structure within that kilometer. For example:

• The 5th structure in the 4th kilometer is designated as 4/5.
• The 8th structure in the 25th kilometer is designated as 25/8.

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Multi-Lane Carriageways

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For multi-lane carriageways, structures can either be combined or separate. If combined, the structure number follows the standard format. If separate, the left-hand side structure is suffixed with ‘L’ and the right-hand side with ‘R’. Service road structures are indicated with an additional suffix ‘S’. For example:

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• Left side structure on service road: 281/2 LS
• Right side structure on service road: 281/2 RS
• Left side structure on main carriageway: 281/2 L
• Right side structure on main carriageway: 281/2 R
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New Structures

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If new structures are built between existing ones, they are numbered sequentially. For instance, a new structure between the 3rd and 4th structures in kilometer 375 would be designated as 375/3/1, 375/3/2, etc.

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Salient Information for Inspection and Maintenance

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To aid in the inspection and maintenance of structures, the following information should be recorded:

• Year of construction
• Name of the channel/river/crossing
• Length of the structure
• Span arrangement
• High Flood Level (HFL)
• Deck Level
• Roadway details
• Type of structure (e.g., RCC, PSC, T-Beam, Box Girder, etc.)

This information should be displayed on a separate plate located on the right-hand side of the carriageway.

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Inscription of Structure Numbers

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Placement of Numbers

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The structure number must be inscribed near the top left-hand side of the parapet wall or railing posts, visible to approaching traffic. In cases where railings are present without supporting pillars, a separate numbering plate (300 mm x 300 mm) should be installed on both sides of the structure.

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Marker Posts for Pipe Culverts

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For structures like pipe culverts that lack parapet walls, two marker posts (150 mm x 150 mm) should be placed on the left side, one for each direction. The culvert number can be engraved or painted on these posts.

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Information Plates

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Size and Placement

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Information plates should be installed in both directions, with sizes varying based on the structure type:

• Minor bridges and culverts: 300 mm x 500 mm
• Major bridges and other structures: 500 mm x 1000 mm

These plates should be affixed near the top right-hand side of the parapet wall or railing.

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Numerals and Details

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The numerals used for structure numbering should be 100 mm high, conforming to the IRC: 30-1968 standards. The background color should be canary yellow (ISI Shade 309), ensuring visibility and compliance with highway signage standards.

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Maintenance of Structure Numbers

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It is essential to keep the structure numbers and information plates updated, clean, and well-maintained. Regular inspections should be conducted to ensure that any changes affecting the existing position are reflected promptly.

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Conclusion

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The IRC: 7-2017 document serves as a vital guideline for the systematic numbering of culverts, bridges, and tunnels across India's road networks. By establishing a uniform numbering system, it enhances asset management, facilitates efficient inspection and maintenance, and ensures that all road structures are easily identifiable. The detailed provisions regarding the inscription of structure numbers, the placement of information plates, and the maintenance of these identifiers underscore the importance of clarity and consistency in managing infrastructure.

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As road networks continue to expand and evolve, adherence to these recommended practices will not only improve operational efficiency but also contribute to the safety and reliability of transportation systems. By implementing the guidelines set forth in IRC: 7-2017, stakeholders can ensure that road structures are effectively monitored and maintained, ultimately leading to better service for all road users.

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