ECONOMIC IMPLICATIONS OF VEHICLE OVERLOADING --HIGHWAY CONSTRUCTION & MAINTENANCE. PROCEEDINGS OF SEMINAR F HELD AT THE PTRC TRANSPORT & PLANNING SUMMER ANNUAL MEETING, BATH UNIV. ENGLAND 7-11 SEPTEMBER 1987, VOLUME P293

The damaging effects of higher axle loads can be met by marginal increase in pavement costs to obtain substantial savings in vehicle operating costs per unit of load. Economic relationships between vehicle loads and pavement costs are not properly understood and there are some misconceptions about damage caused by heavy goods vehicles. The damaging effect of load varies by 4.5th power of the ratio of a given load to the standard load; pavement strength varies with thickness by a power of ten while pavement costs vary linearly with thickness; and vehicle operating costs vary inversely with load. Accordingly, increase in damaging effect due to higher load can be met by a much smaller increase in pavement costs to obtain substantial savings in overall transport costs. This aspect has been neglected so far. Restrictions on loads would require more vehicles and more road space to carry the same load. This would cost relatively more than strengthening of roads as, in the first case, cost of land, sub-base, base and surface would have to be incurred while, in the second case, only increase in thickness of pavement would be required, the cost of which would be marginal. Therefore, a policy of imposing restrictions on loads would end up in higher pavement costs for a road authority and higher transport costs for road users. The paper traces the effects of loads on pavement and vehicle operating costs, compares the two to arrive at an optimum level, clarifies issues and recommends policy measures to minimise overall costs. Optimum pay loads have been found to vary with volume of traffic and strength of road and are far higher than present limits or existing loads. The overloading of vehicles is a blessing in disguise as it saves both pavement and vehicle operating costs. The poor condition of roads in Pakistan is due to inadequate specifications. A policy of strengthening the roads which would be needed any how, rather than restrictions on loads, is recommended.(a) for the covering abstract of the seminar see IRRD 816254.