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The public debate over the most appropriate seat design to best protect occupants at all rear impact speeds is more than an decade old. There have been numerous publications in the technical literature discussing the relative merits of lower versus higher seat back strength. Proponents of lower seat back strength assert that the larger rearward deformation of seat backs allowed by most current seats is less injurious to the seats’ occupants than seats with higher seat back strength. However, proponents of higher seat back strength assert that stiffer seat backs provide greater overall safety benefits to occupants of the seats and also protect passengers that may be seated behind them. The current study used a modified version of a validated MADYMO computer model of a 1986–1994 GM Grand Am production seat, originally developed by the University of Virginia (UVA), to determine the effect of seat back strength on occupant injury in rear impacts.

Since 1994, the New Car Assessment Program (NCAP) of the National Highway Traffic Safety Administration (NHTSA) has compiled upper neck loads for the belt and air bag restrained 50th percentile male Hybrid III dummy. Over five years from 1994 to 1998, in frontal crash tests, NCAP collected upper neck data for 118 passenger cars and seventy-eight light trucks and vans. This paper examines these data and attempts to assess the potential for neck injury based on injury criteria included in FMVSS No. 208 (for the optional sled test). The paper examines the extent of serious neck injury in real world crashes as reported in the National Automotive Sampling System (NASS). The results suggest that serious neck injuries do occur at higher speeds for crashes involving occupants restrained by belts in passenger cars.