Head, face and neck (HFN) injuries associated with upper interior contacts account for a large percentage of all serious to fatal injuries annually. In the past, many of these injuries were the result of unrestrained occupants in rollovers and side impacts. Mandatory belt use laws have helped keep the head and torso inside the vehicle, but HFN injuries in side and rollover accidents persist. Regulatory actions for side and rollover protection deal with torso injuries but head injuries have been addressed only by upper interior padding.

Rollovers have been characterized as violent events and roof crush as the natural consequence of such violence. The original claims were based in part on the “Malibu” experiments, which suggested that head and neck injuries for occupants are unavoidable even with improved roof strength and the use of production restraints.

An analytical effort to understand rollover injuries, using the field accident data of the NASS files and residual headroom as an indicator, was reported by the authors at the 1996 ESV conference in Melbourne, Australia. This work led to a revised theory of rollover head, face and neck (HFN) injury mechanisms and their relationship to, for example, roof crush, headroom, restraint excursion, padding, glazing and vehicle geometry. In an effort to investigate both the original claims and the revised theory, some additional analyses were conducted and a series of experiments were devised.

This paper briefly summarizes the previous work, describes further analyses and experimentally identifies the low crash severity, roof crush, padding and restraint relationship to HFN injury, through physical, computer, and volunteer occupant tests.

The conclusion is that a causal relationship exists between HFN injury and occupant protection system design and performance (including, for example, roof intrusion, vehicle geometry, headroom, restraint excursion, glazing, upper interior padding in combination).