Relationship for estimating vehicle operating costs on paved and unpaved roads in developing countries

The caribbean study was conducted along similar lines to the first full scale field investigation into vehicle operating costs carried out in kenya and was designed to complement that study. The vehicle performance study provided a new set of relationships for estimating vehicle speed and fuel consumption. The severe terrain in which the study was conducted in st lucia produced speed estimating equations of a different order of magnitude to the existing kenya relationships. A method has been evolved to make use of these two sets of relationships to provide realistic vehicle speed estimates for intermediate physical and environmental conditions. The fuel consumption relationships derived from the st lucia study provide improved estimating equations over a larger range of operating conditions. The major differences between the two sets of user survey relationships are the significantly higher effect on spare parts and tyre consumption of a deteriorating bitumen surfaced road compared with a gravel road of the same surface roughness, and the lower rate of depreciation of heavy vehicles. The two sets of relationships have been combined and modified to make them suitable for inclusion in the new TRRL rtim2 model. They can be used to study various aspects of a road investment programme such as the optimum maintenance standards for the road or the effects of providing a paved or unpaved surface (a).