The automotive crash environment and the safety systems that operate within it present an extremely complex loading environment to vehicle occupants. Responses of the equally complex human structure to this loading environment determine whether or not an injury hazard is presented to the occupant. As improved, more efficient. and more economical performance is sought from automotive safety systems, the criteria and test devices that evaluate their performance must have greater capabilities. This paper addresses NHTSA's rationale and current research efforts to develop and provide enhanced, mechanically based, injury sensing criteria for the head, thorax, and other body regions The techniques and processes being developed to allow their application in the physical testing environment are also discussed.