The Effect of Obesity on Rollover Ejection and Injury Risks

Obesity rates are increasing among the general population. This study investigates the effect of obesity on ejection and injury risk in rollover crashes through analysis of field accident data contained in the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) database. The study involved front outboard occupants of age 15+ years in 1994+ model year vehicle rollover crashes. Occupants were sorted into two BMI groups, normal (18.5 kg/m² ≤ BMI < 25.0 kg/m²) and obese (BMI ≥30 kg/m²). Complete and partial ejection risks were first assessed by seating location relative to roll direction and belt use. The risk of serious-to-fatal injuries (MAIS 3+F) in non-ejected occupants were then evaluated. The overall risk for complete ejection was 2.10% ± 0.43% when near-sided and 2.65% ± 0.63% when far-sided, with a similar risk for both the normal and obese BMI groups. Complete ejection was highest for unbelted occupants, irrespective of BMI, and uncommon for belted occupants with a risk of 0.2% or less for all belted groups. The risk of partial ejection was greater for obese compared to normal BMI occupants. For near-side occupants, the overall risk of partial ejection was 2.24% ± 0.70% for normal BMI and 3.56% ± 0.50% for obese occupants (p>0.10). The corresponding risk for was 1.27% ± 0.31% and 3.42% ± 0.83% for far-side occupants (p<0.01). Belt use was effective in reducing ejection risks for all occupants. The effectiveness was lowest for obese near-side occupants. The risk of serious-to-fatal injury for non-ejected occupants was lower when belted than unbelted, irrespective of BMI group. The overall risk was higher for obese than normal BMI occupants, especially for the near-side position. The results of this study suggest differences in occupant responses with increasing BMI for individuals involved in a rollover crash. Further research on the effects of increased BMI on occupant responses is needed.