In two previous SAE papers (1,2) by the authors, supporting analysis was presented showing the difficulty in achieving a timely response to real-crash events using a single point sensor mounted in the non-crush zone of the vehicle (tunnel, cowl, etc.). The analysis demonstrated the propensity to deploy the air bag(s) late during certain of these events. If a vehicle occupant was not wearing a safety belt, the deceleration forces of the crash could place the occupant out of position and resting against the air bag when it was deployed. In another SAE paper (3) by H. J. Mertz et al, the authors demonstrated that animals, used as surrogates for humans, could be injured if positioned against an air bag at the time of deployment.
Arguments are presented here to show that there is insufficient information in the crash pulse as sensed in the non-crush zone to deploy an air bag in time for the unbelted occupant. It is therefore not possible to create an algorithm for an electronic sensor, based on the crash pulse information in the non-crush zone alone, which will initiate air bag deployment in time for all cases. Therefore, sensing in the crush zone is required.