The Collision and Trajectory Models of PC-CRASH

PC-CRASH is a windows^o-based accident-reconstruction program which combines the simulation of pre-collision, collision, and post-collision dynamics for multiple vehicles in a graphical environment. This paper presents the trajectory and collision models on which PC-CRASH is based. PC-CRASH'S model for predicting the 3D kinematics of a vehicle's pre- and post-impact trajectory, which is based on a discrete- kinetic time forward simulation of vehicle dynamics rather than empirically-derived “spin-out coefficients”, is described. The tire-force model (which accommodates ABS), steer angle, wheel braking, weight shift, and suspension effects are introduced and the program's method of handling pre-impact yaw, braking, acceleration and pre-impact steering is outlined. The momentum-based collision model, which relies on restitution rather than vehicle crush or stiffness coefficients, is defined and the program's method for dealing with secondary impacts, inter-vehicle friction, and impulse vectors with a vertical component is explained. The paper concludes with a simple reconstruction which demonstrates the various models and the program's built-in 3D animation capabilities