Risk of injury and fatality in single vehicle rollover crashes: danger for the front seat occupant in the "outside arc".

BACKGROUND

Rollover crashes are responsible for a large portion of motor vehicle occupant injuries and fatalities.

OBJECTIVES

To examine if there is an increased risk of injury or death for either front seat occupant depending on the direction the vehicle rolled over.

METHODS

Between 1992 and 2002, crash data were collected and analyzed from the National Accident Sampling System Crashworthiness Data System (NASS/CDS) database of police reported tow-away crashes in the United States. These data were limited to information concerning single vehicle crashes with right or left initial rollover, in which both driver and front seat passenger were present and secured with lap-shoulder belts. The "outside arc" occupant was defined as the occupant who underwent the greatest degree of initial rotational torque during the rollover. Crashes involving sport utility vehicles (SUVs) were further evaluated for risks of injury or death based on the direction of the initial rollover. The location of roof crush and the types of injuries were also analyzed for these rollovers. This weighted database allows for the calculation of mortality and injury prevalence in the population.

RESULTS

There was a significantly higher fatality rate for outside arc occupants than inside arc occupants in rollover crashes. The weighted percentage fatality for the occupant on the outside arc for all classes of light passenger vehicles was 0.38%, while the percentage fatality for the occupant on the inside arc was 0.23% (odds ratio [OR], 1.64; p = 0.04). As a subgroup, the SUV class showed a weighted outside arc fatality percentage of 0.23%, while the inside arc fatality percentage was 0.02% (OR, 10.69; p = 0.06). Additionally, in SUVs, the weighted percentage having an Injury Severity Score of 9-75 was 0.99% for the outside arc passengers but only 0.19% for the inside arc passengers (OR, 5.42; p = 0.04). Roof crush was located more commonly on the outside arc of the rollovers than on the inside arc (42% vs. 26.3%; p < 0.01). There was a trend toward increased head and neck injuries in the fatal rollover crashes when compared with fatalities in the entire NASS/CDS database (91% vs. 58%; p = 0.06).

CONCLUSIONS

The risk of death for outside arc occupants was higher than for inside arc occupants in rollovers. In addition, outside arc occupants in SUV rollover crashes were more likely to incur moderate or severe traumatic injuries. Roof crush occurs more commonly on the outside arc, and head and neck injuries were more prevalent in rollover crashes.