Computation of run-off-road vehicle speed from terrain tracks in forensic investigations

Analysis of a “run-off” accident requires a knowledge of the physical properties of the soil, otherwise any evaluation can only be approximate. In order to reconstruct a run-off accident one must examine the soil’s mechanical parameters and create a soil database. The purpose of our project was to make measurements for a later soil database and a computer simulation to determine the speed of a vehicle at the point where it left the road. A series of measurements were performed for this purpose at the Department of Automotive Technology of the Szent István University to obtain data for a soil database as part of a project to develop a run-off-the-road accident simulation model. The model is designed to determine the speed of the vehicle as it leaves the road. Knowledge of this speed is crucial in the investigation of such accidents, and investigators have to estimate it from vehicle tracks left on the road and on the adjacent terrain. The model may be validated and verified by determining the soil–vehicle resistances on relevant terrain. In our paper we introduce a set of computations capable of computing the vehicle’s initial velocity.

Highlight
► Our aim is to determine the speed of a vehicle at the moment it runs off the road.
► The run-off speed depends on travel resistances and distance traveled on terrain.
► The results show that rolling resistance decreases as cone index increases.
► On loose soils coefficients of rolling resistance are higher than on hard surface.
► Change in coefficient of bulldozing resistance is related to the soil cone index.