The vehicle-occupant impact dynamics during a crash are studied using a simple mathematical model. The model yields explicit analytical relationships between occupant responses and physical parameters of the vehicle structure and occupant restraint system. These parametric relationships, verified by experimental crash tests of the total system, are useful in describing the physical concepts of the impact event, and predicting occupant dynamic behavior during a vehicle crash. The limitations of the model are discussed and the design procedures using the equations and “carpet” plots are presented to aid the designer in the selection of a restraint system and vehicle structural parameters to meet predetermined design criteria. The application of the “carpet” plot in studying the sensitivity of the occupant response to the vehicle structural parameters is also demonstrated.