Abstract
This report gives the results of an investigation carried out into the way the fuel consumption of ix vehicles ranging from a small saloon car to heavy articulated lorry varied with road conditions Measurements were carried out over a wide range of traffic conditions on different types of roads. From the results obtained, a curve giving the variation of averaged fuel consumption with traffic speed has been derived for a traffic stream of average composition. The relevance of the results to cost-benefit analysis of road improvement schemes is outlined.