The purpose of the study described in this report was to evaluate the effect of vehicle power to weight ratios on the speeds of commercial vehicles operating in different types of terrain in developing countries. The results of the study undertaken in Ethiopia show that the speeds of medium and heavy goods vehicles are considerably influenced by the power to weight ratio of the vehicle in addition to the physical characteristics of the road, but that the speeds of buses are apparently influenced only by the physical characteristics of the road. The effects of vehicle characteristics on speed that were successfully identified in this study have been used to modify the speed-estimating equations in the road transport investment model for developing countries. (Author/publisher)
Abstract