Head and Neck Injury Potential in Inverted Impact Tests

The National Highway Traffic Safety Administration (NHTSA) has concluded that there is a relationship between roof intrusion and the injury risk to belted occupants in rollovers. Roof crush occurs and potentially contributes to serious or fatal occupant injury in 26% of rollovers. The inverted drop test methodology is a test procedure to evaluate the structural integrity of roofs under loadings similar to those seen in real world rollovers. Drop test comparisons have been performed on over 20 pairs of production and reinforced vehicles representing a large spectrum of vehicle types. The structural modifications in the reinforced vehicles maintained the occupant survival space and seat belt geometry. This paper analyzes inverted drop testing performed on several production and reinforced matched vehicles with restrained Hybrid III test dummies. Review of neck load data indicates that reduced roof crush results in a direct reduction in neck load, thereby increasing occupant protection. Restraint loading and performance, relating to roof structure integrity, is also evaluated.