Limiting performance of seat belt systems for the prevention of thoracic injuries

The theoretically optimal performance of seat belt systems for occupants in automobile frontal crashes is investigated based on a two-mass injury mode l of the thorax. The performance is measured by thoracic injury criteria wh ich include: the maximum chest acceleration, compression and viscous respon se. The relationship between the best possible performance (limiting perfor mance) of the seat belt system and the distance between the occupant and th e interior components of the vehicle is displayed in the form of trade-off curves, which can be Used for the evaluation of seat belt performance. The characteristics of the optimal seat belt force and the kinematics of the sy stem are illustrated. The results indicate that the optimal seat belt force is not constant during an impact and that an initial impulse is required. However, constant seat belt force can provide thoracic restraint that is cl ose to the optimal solution.