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Inverted drop testing of vehicles is a methodology that has long been used by the automotive industry and researchers to test roof integrity. In our laboratory, the inverted drop test methodology was employed on late model production vehicles to simulate the damage incurred by a real world rollover accident. The extent and shape of residual damage matched well with the corresponding accident damage. Modified vehicles were reinforced based upon previously documented techniques. Incorporation of these techniques demonstrated a significant increase in roof strength and corresponding reduction in roof crush with minor weight addition. Finally, a production vehicle and structurally enhanced vehicle were drop tested with instrumented Hybrid-III occupants. This pair of tests confirms that reduction of roof intrusion and increased headroom can significantly enhance occupant protection. It also highlights the need to maintain adequate survival space for the vehicle’s occupants.

The government, automotive industry and scientific community are currently scrutinizing the adequacy of the FMVSS #216 roof crush standard in the United States. As a result of concern about the ability of FMVSS #216 to enforce reasonable protection to occupants in rollovers, The National Highway Traffic Safety Administration (NHTSA) has recently published a Request For Comments in the Federal Register regarding updating this standard1. The inverted drop test methodology is a promising alternative test procedure to evaluate the structural integrity of roofs and is being considered by NHTSA as a possible compliance test. Recent testing on many different vehicle types indicates that damage consistent with field rollover accidents can be achieved through inverted drop testing at very small drop heights. Drop tests matrices were performed on 9 pairs of vehicles representing the majority of personal transportation vehicle types.

In this study we continue and build upon previous research conducted with various production three-point restraint systems; studying resulting vertical excursion on restrained inverted occupants. Vertical excursions will be reported for various sized occupants restrained by both production vehicle belt systems as well as systems incorporating alternative designs. Vertical excursions have been reduced by an average of 77% with optimized belt geometry combined with belt pretensioning.