Analyses of some of available experimental results suggest that frontal and rear-end automobile collision processes may be simulated by a simple model with a mass, which represents the vehicle mass, and a spring, which represents the resisting force due to crushing of the vehicle structure. Indications are that in the case of barrier and head-on collisions, the spring is one-way linear, and the rate does not vary with colliding speeds provided that the type of vehicle and the mode of collisions remain the same. On the other hand, in the case of rear-end collisions, experiments indicate that the spring is almost rigid-plastic. The occupant's motion was also studied by a simulated model. A parametric study was made to obtain a design criterion for safety harnesses and vehicle interior geometry relative to occupants for injury reduction.