Inverted drop testing as a mechanism to evaluate rollover occupant injury potential

The National Highway Traffic Safety Administration (NHTSA) has concluded that there is a relationship between roof intrusion and the risk of injury to belted occupants in rollovers events [1]. Previous testing on many different production vehicle types indicates that damage consistent with field rollover accidents can be achieved through inverted drop testing from small drop heights. It has been shown in previous drop test pairs with Hybrid III dummies, that the amount of roof intrusion is related to occupant neck injury [2,3]. In 1990, a study was reported by General Motors which involved 8 dolly rollover tests and 5 inverted drop tests performed on both production and rollcaged vehicles with Hybrid III dummies [4]. These studies were conducted to investigate the relationship between roof strength and occupant injury potential. In this paper, the authors further analyze the relationship between roof intrusion and occupant neck injury potential through inverted drop testing performed on Ford Econoline E-350 15-Passenger production and reinforced vans. Each of these van tests used Hybrid III test dummies in order to evaluate the resulting occupant injury potential in relation to the roof intrusion. The resulting roof intrusion and occupant neck loading experienced during the reinforced van drop test were significantly less than that of the production van test. As previously observed, the results of these tests indicate that the reduction of roof crush resulted in a direct reduction in neck loading and therefore an increase in occupant protection. Additionally, the inverse relationship between restraint loading and neck loading of the dummies was confirmed.