Parametric studies are used to provide design direction for improved occupant performance in a crash event. Design of experiments analysis techniques and optimization algorithms provide quantitative information from such a study. An analysis technique is being used which provides qualitative information, helping to explain the physics of the problem. Understanding the physics provides scientific answers to the questions why and how when assessing the effects of parameter changes. This technique allows the dissection of the restraint system into components, providing insight to the contribution of each component's energy absorption to the occupant's overall response. Data from instrumented experiments or simulations are used to describe the management of the occupant's kinetic energy in a crash. The use of this technique is first demonstrated using a simple parameter study of a passenger side air bag system. An analysis of a driver side restraint subsystem illustrates the dissection of the subsystem into its components. Energy transfer within the occupant is also measured and can provide information on restraint system effectiveness. A design process is then suggested which would provide a complete (quantitative and qualitative) understanding of the restraint system as it is developed.