Analytical Model to Determine the Influence of Horizontal Alignment of Two-Axle Heavy Vehicles on Upgrades

Abstract

Existing design policies determine the speed variation of vehicles on upgrades solely as a function of specific values: initial speed, grade, and weight to power ratio. This paper establishes a dynamic model that considers in addition the influence of the roadway’s horizontal alignment. The model was validated on both tangents (using existing speed-distance profiles and similar simulation models) and curves (by an existing simulation model and field measurements). The model output was examined on a roadway alignment. It was found that sharp horizontal curves influence the speed of heavy vehicles significantly on mild upgrades. Therefore the conventional speed profile determination has to be supplemented by incorporating the horizontal alignment as well. The proposed model can be used to provide solutions in a more efficient and realistic way than does the current practice.