The program PC-CRASH was developed for the reconstruction of vehicle accidents and considers pre-impact, collision and post-impact phases. The present paper describes the physical and mathematical model which was added recently to PC-CRASH in order to enable the simulation of the dynamic behavior of articulated vehicles (with both single and double axle semi-trailers and with steered trailers). The trailer model, a discrete kinetic time forward simulation, builds on the vehicle and trajectory models described and validated earlier. The dynamic interaction of the towing vehicle and the trailer is outlined and the governing equations for the vehicle-trailer connection and the determination of the hitch force are presented. The momentum based collision model, relying on restitution rather than vehicle crush, is extended to simulate those vehicle collisions involving trailers. The ability of the model to predict speed-dependent off-tracking is demonstrated. Sample cases showing some typical trailer movements are presented and discussed.
