Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
The purpose of weighbridge is to control overloading and thus protect the road pavement. A weighbridge is economical if the saving in pavement maintenance is greater than the costs of the weighbridge. The saving depends on the length of road that the weighbridge controls. A measure of weighbridge economy - the so-called break-even length - has been introduced and derived from the equality of weighbridge costs and pavement maintenance savings. The break-even length depends on several factors of which the type of pavement, distribution of axle loads, magnitude of heavy-vehicle traffic, width of the pavement to be protected, cost of pavement maintenance, and the weighbridge operating cost are particularly important. For bituminous pavements the break-even length is about 50 km for volumes of heavy vehicles ranging from 200 per day to 3 000 per day. For volumes over 3 000 HV/day maintenance intervals become impractically short and a concrete pavement should be used instead of bituminous one. In case of a concrete pavement the break-even lengths are enormous – several thousands of kilometres – indicating that the cost of a weighbridge exceeds by far the savings in road maintenance. Although potentially beneficial from other points of view, a weighbridge on a concrete road cannot be justified in terms of reduced pavement maintenance.