Since the 1984 publication of the results of NHTSA's initial research on thoracic side impact protection, substantial progress has been made. Specifically, the NASS data have been reviewed relative to side impacts, an updated injury criterion has been developed, the MVMA has conducted a very significant crash test project, and the NHTSA has conducted additional full system production vehicle tests.The review of the NASS data and a comparison with the previously used NCSS data indicate the thoracic injury remains the highest ranking injury in non-rollover, non-ejection side impacts.The updated injury criterion, TTI-86, is applied to the side impact dummies in the modified vehicle tests which have been conducted by NHTSA and MVMA. The TTI-86 is also applied to twenty production vehicle tests which have been conducted by NHTSA. The improved performance of the modified vehicles is compared to the average performance of the twenty production vehicles. This comparison indicates the potential for significant safety improvements for reducing thoracic injuries in side impact collisions for the given test conditions and crash severities and for several of the production vehicles that have been tested.