Estimates were made of the effects of observed differences in the crash responses of small and large cars on the likelihood of injury to unrestrained occupants in small car-small car and large car-large car head-on collisions using a simple spring-mass model. Two measures of the likelihood of injury were computed: the relative velocity of an unrestrained occupant and car at the instant the occupant strikes the interior, and the approximate closing speed at which occupant compartment intrusion would be expected to begin. Model estimates of the intrusion thresholds for large car-large car and small car-small car head-on crashes were comparable. However, unrestrained occupants were predicted to strike the interiors of their cars at a lower relative velocity in a head-on crash involving two large cars than in a similar crash involving two small cars. Head-on crashes involving a large and small car were also modelled for purposes of comparison. The estimated intrusion thresholds for small cars in such crashes were considerably lower than in small car-small car crashes. Also, calculations indicated that in a small car-large car head-on crash, an unrestrained small car occupant strikes the interior of his car with a higher relative velocity than an unrestrained large car occupant, and this velocity is higher than if his car struck another small car. However, the difference in the relative velocities with which unrestrained small and large car occupants impact the interiors of their cars in small car-large car collisions was found to diminish with increasing closing speed. These results suggest that the frontal structures of small cars should be longer and less stiff than on current models and the occupant compartment should be stiffer. Such designs would help to reduce injuries to restrained and unrestrained small car occupants in collisions with both small and large cars.
1. . A. ZAREMBA
In developing countermeasures to reduce such losses, an understanding of why crashes involving two small cars result in more frequent and more severe injuries than crashes involving two large cars is important. In this study, differences in the frontal dynamic crash response of recent models of foreign and domestic cars of various sizes were examined using data from barrier crash tests, and estimates were made of the effect of the observed differences on the likelihood of occupant injury in small car-small car and large car-large car crashes using a simple spring-mass model. Crashes involving a large and small car were also modelled for purposes of comparison. All comparisons were made for head-on crashes only. Adequate data regarding the side and rear crash behavior of a sufficient variety of cars were not available to enable a similar analysis for front-to-side and front-to-rear crashes. Also, only unrestrained occupants were considered. This is consistent with the crash studies cited above in which the occupants were either reported to be unrestrained, or their use of restraints was unknown, and they were thus also most likely unrestrained.