Considerations for Rollover Simulation

Rollover crashes are responsible for a significant proportion of traffic fatalities each year, while they represent a relatively small proportion of all motor vehicle collisions. The purpose of this study was to focus on rollover events from an occupant's perspective to understand what type of industry test method, ATD, computer based model, and injury assessment measures are required to provide occupant protection during rollovers. Specific injuries most commonly experienced in rollovers along with the associated injury sources were obtained by review of 1998-2000 NASS-CDS records. These data suggest that models capable of predicting the likelihood of brain injuries, specifically subarachnoid and subdural hemorrhage, are desirable. Ideally, the model should also be capable of predicting the likelihood of rib fractures, lung contusions and shoulder (clavicular and scapular) fractures, and facet, pedicle, and vertebral body fractures in the cervical spine. Such predictive capabilities would require the development of new models and injury assessment values. The NASS data also indicated that neck injury normally occurred without concomitant brain injury or skull fracture. On the other hand, most of the time when there was a skull fracture there was also a brain injury, while only half of all brain injuries occurred with a concomitant skull fracture. These suggest the likelihood of both contact and non-contact related brain injury. Somewhat surprisingly, the distribution of MAIS and injured body regions for non-ejected occupants of vehicles that rolled did not vary widely between rollovers of ¼, ½, and ¾ + turns. Analysis of the distribution of rolls revealed that 50% of rollovers involved ½ or less turns, 75% are 1 full roll or less and that ejection risk and the risk of neck injury increased with the number of ¼ turns. Based on these data, two design points are recommended. The first is a 2-4 quarter turn rollover with sufficient energy to induce roof crush. The second is a 2 roll simulation to evaluate ejection prevention strategies and injury potential.