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At least 160 reports and documents have been written on rear impact crashes and occupant protection since 1964. Reviewing automotive crash safety research has identified the importance of reducing relative motion between the head, neck, and torso. Although rear impact accidents produce relatively few severe injuries, National Automotive Sampling System (NASS) Crashworthiness Data System (CDS) data base analysis has determined that rear impact accidents are second only to frontal impacts in terms of cost to society.

An extensive study was conducted studying the optimization of seat belt and airbag systems for simultaneous use during an accident. It is an objective of this study to develop an understanding of restraint system interaction and the compromises required for the individual systems to optimize the total response. The study entailed over one hundred full scale dynamic tests controlling seat belt and airbag attributes carefully and varying these attributes methodically. The study shows that significant reductions in occupant injury criteria are possible by tuning the seat belt characteristics predominantly to approximate an ideal belted restraint system. These so called “Constant Force Restraint Systems” can be further expanded to include new levels of pretensioner performance thereby allowing significant injury criteria reduction without increased head or chest excursions.

A study was conducted utilizing both math modeling and dynamic barrier simulations studying restraint system optimization for an adaptive restraint system. An adaptive restraint system is one which can adjust its characteristics based on some knowledge of the crash environment such as occupant size, crash severity, and occupant position. The restraint system characteristic can be optimized based on a constant force restraint system, that is a restraint system which provides a constant restraint force for the occupant over the entire range of occupant motion. Such a system normally results in a minimization of peak restraint forces as well as peak chest accelerations and maximum chest compression. Constant force restraint systems are normally achieved through high output pretensioning, initially stiff belt systems, load limited torso belts, and a carefully tuned airbag inflation and venting characteristic.