Influencing factors on the injury severity of restrained front seat occupants in car-to-car head-on collisions.

The results of 319 cases of belt-restrained front seat car occupants (234 drivers and 85 passengers) from 241 vehicles in car-to-car head-on collisions were examined. Ninety-five occupants were uninjured, 195 sustained a total injury severity of Maximum Abbreviated Injury Score (MAIS) 1-3 and 29, MAIS 4-6. There were 27 fatalities, and the main causes of death were polytrauma and hemorrhage. The main factors influencing occupant injury severity were: the energy equivalent speed (EES); the change of velocity (delta upsilon); the maximum deformation depth; and the collision angle. With an EES > 50 km/h fatal injuries can be expected, and above 60 km/h no occupant remained uninjured. The results of a multivariate analysis were: EES influenced the injury severity at all body locations except the spinal cord; occupant position effected only head injury severity, with drivers being more severely injured; occupant age influenced the injury severity at the thorax, abdomen, and extremities and MAIS as well. Age was a further factor influencing injury severity, e.g. with an EES of 50 km/h the probability of being fatally injured was 30%-45% higher for occupants over 59 years than those under 20.