Axle and Wheel Loads in Developing Countries and Consequences for Material Specifications (05-0326)**
André Molenaar, Delft University of Technology, Netherlands

Overloading of trucks is a serious problem in developing countries. It results in high axle and wheel loads which have a devastating effect on the pavement structure. It is common practice to express the damaging effect in terms of an equivalent number of standard axle loads. The question arises whether this is a useful approach in case of overloaded trucks. The reason for this doubt is because of the fact that due to poor maintenance of the trucks, improper loading etc, wheel loads might occur which are much higher than the axle load divided by the nr. of wheels. Furthermore contact pressures might be excessive because of high tire pressures that have to be used because of overloading. This paper describes the results of a rather extensive axle and wheel load survey that took place in Ghana in the early 1990’s. It will be shown that axle load measurements are not sufficient at all to determine the magnitude of the overloading problem. Wheel load and tire pressure measurements should always be part of surveys into the overloading of trucks. Furthermore it will be shown how material specifications should be increased in order road pavements to be able to sustain excessive loadings.