An extensive research program to evaluate the feasibility of improved side impact protection has been conducted by the National Highway Traffic Administration. This program concentrated on the potential reduction in thoracic injuries to vehicle occupants in side impact.Test conditions, test procedures, and test hardware for evaluating thoracic side impact protection were defined, developed, and evaluated. Injury mitigation concepts which included vehicle structural modifications and the addition of padding to the inner door surface were developed and evaluated. Test results support the feasibility of providing significant improvements in thoracic side impact protection.In addition, side impact tests were conducted on ten production automobiles. Results from these tests indicated a relatively low injury potential for occupants in some vehicles and a very high injury potential for occupants in other vehicles. This large range of performance suggests that side impact improvements needed by some of the vehicle fleet are within the state-of-the-art.