RECOMMENDED DESIGN OF PAVEMENTS, GOVERNED BY THE TRAFFIC DENSITY AND THE WIDTH OF THE CARRIAGE WAY FOR HILL ROADS.

The design of pavement is governed by the traffic density, ie the number of vehicles using the road during peak hours, and the maximum wheel load. The daily traffic volume is about 8 to 10 times the maximum hourly volume. Character of the traffic and the speed of vehicles are also major considerations. Rate of traffic increase per annum is also to be considered and which may vary from 10 to 20 percent in a developing country like India. As such land width required is the total width to accommodate the road way, berms, drains and width reserved for future developments. Maximum land width is exclusive of land required for the borrow pits, while desirable land width includes land for borrow pits. Formation width is carriage way plus shoulders. It is the top width of embankment or bottom width of cutting excluding the side drains. In open country roads, earth berms need to be provide of width 1.8 m minimum on each side. The width of the separate parking lane, where ever provided may be kept 3 m. The carriage way intended for one line of traffic movement is generally half of the total width of the carriage way however increase of width is required on approaches to towns and areas to provide for the increase in traffic. The roadway widths given above are exclusive ol the parapets usual width 0.6 m and the side drain usual width 0.6 m and these should be provided in addition to the shoulders as necessary. In hard rock stretches, the width of the shoulders may be reduced by 0.4 m on either side on double lane roads and 0.2 m in other cases. The full roadway widths should be carried through on culverts, scuppers and the causeway. The roads subject to heavy snow fall, where regular snow clearance is required over long periods to keep the road open to traffic, roadway width may be increased by 1.5 m for district roads and the village roads. (Based on IRC:52-1981& 70-1977).