Abstract
The relation between occupant deceleration and injury is briefly considered and an Injury Index is proposed. A simple representation of side impacts leads to some assessment of the factors that determine the velocity with which the occupant strikes the side of the passenger compartment. If the interior structure could be arranged so that belt wearers were completely restrained by their belts in moderate impacts, but additionally supported by an energy absorbing structure during severe impacts, worthwhile protection would be provided for the unrestrained occupant and additional protection given to the belted occupant.