Limitations of the flexible pavement design method laid down in IRC-37 are apparent in the light of the current state of technology in pavement design. Its basic deficiency is that it does not take into account the sensitivity of a pavement to wheel-load magnitude beyond a certain value implicit in the design method. The method considers the traffic variable in terms of the number of commercial vehicles which is not a precise characterisation of commercial traffic for physical input to design as evident from the well-known fourth-power axle-load damage relationship. A recently concluded pilot study of axle-load spectrum on the National Highway Network in the country shows that the vehicle damage factor (standard axles per commercial vehicle) varies from a modest value of 0.6 in Kerala to an alarming value of 7.8 on some N.H. sections in Uttar Pradesh. Besides, the recent amendment to the Motor Vehicles Act, 1939 now permits a maximum safe axle weight of 10.2 Ton single axle. Its consequence in terms of road damage is reflected in its axle equivalence factor of 2.4 as against 1.0 of the earlier permissible load of 8.2 T. The current design method does not respond to these variations in axle-loading. As the pavement performance is a function of the wheel-load magnitude and frequency, in the raffic flow, technical expediency demands that the factual data on vehicle damage factor is used to quantify traffic input to design and to make more objective pavement design decisions. With this objective in view design curves relating pavement thickness to design life in cumulative standard axles need to be developed for immediate use. (Author)

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  • Corporate Authors:

    Indian Roads Congress

    Jamnagar House, Shahjahan Road
    New Delhi,   India  110 011
  • Authors:
    • Sivaguru, N
    • Sharma, S C
  • Publication Date: 1983-12

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Filing Info

  • Accession Number: 00389120
  • Record Type: Publication
  • Report/Paper Numbers: Paper No. 360
  • Files: TRIS
  • Created Date: Oct 30 1984 12:00AM