Data on towaway accidents involving 1973, 1974, and 1975 American passenger cars were collected according to a systematic sampling plan to measure restraint system performance. The data on over 9,000 drivers and right-front passengers were collected by the Calspan Corporation, the Highway Safety Research Institute, and Southwest Research Institute. While an earlier analysis considered injury patterns in terms of the rate of occurrence of specific injuries, this study explores injury patterns in terms of the injury severity to occupant body regions, e.g., the percent of occupants with an AIS-2 or greater head injury as a function of restraint usage.

Analyses of the data showed that higher percentages of occupants were restrained--by either the lap belt alone or full restraints--in both 1974 and 1975 cars than in 1973 cars. While full restraint usage was less frequent in 1975 cars than in 1974 models, it was still more than seven times more frequent than in 1973 models. When adjustments are made for differences in crash severity, the results showed that occupants using restraints incurred substantially fewer moderateor-worse injuries than unrestrained occupants. Fully restrained occupants fared better than those using only a lap belt.

Injury patterns were described in terms of the percentage of occupants sustaining lesions by body region and injury source. Restrained occupants received fewer specific injuries (per person) than unrestrained occupants. Restraint systems were more effective in eliminating moderate-or-worse injuries than they were in preventing minor injuries. Fewer restrained occupants received injuries to the head, face, extremities, and chest region, but more received minor neck, abdominal, and pelvic-region injuries. Full restraints reduced the frequency of injuries from the steering wheel and column and front interior, but did not eliminate them. Moderate-and-worse injuries attributed to the restraint system were extremely rare.