This bulletin documents the work on estimating the power/mass ration (p value) for heavy vehicles. The aim of the work was to estimate p values for heavy vehicles, broken down into three main types: (1) lorries without trailers and all buses; (2) lorries with trailers, 3-4 loaded axles; and (3) lorries with trailers, 5-9 loaded axles. The estimates were to be compared with previous measurements and the new results implemented in the VTI traffic simulation model. In order to obtain data for the estimates, journey time measurements were made on two uphill sections. The power/mass ratio was estimated using a model based on Newton's second law of motion. A total of 3 879 vehicles were analysed with respect to speed change between the measuring points on the incline. The results show that for all types of heavy vehicles the p value has increased since 1974. This means that the increased limit for maximum permissible load is more than compensated for by increased engine power. The largest verified increase was noted for lorries without trailers and all buses. The new p value distributions are now used in the VTI traffic simulation model and also in other models at VTI. (A)
Abstract