When an understanding of complex motions associated with various accidents is required, computer simulation is an invaluable tool, which allows the modeling and visualization of rollovers and collisions. In addition to vehicle accidents, computer simulation can also be used to create many other systems of masses and contacting surfaces, such as a toppling light pole after it has been struck. Simulation can reconstruct the motion of a falling I-beam at a construction site or determine the jack-knife behavior of an articulated truck. Such modeling can determine the speeds and forces during an event and can even predict how an event accident could have been avoided.