SUV rollover in single vehicle crashes and the influence of ESC and SSF

The modern Sport Utility Vehicle (SUV) fleet continues to go through a transformation in response to the concern that they are at an increased risk of rollover. Our research objective was to look at changes in rollover rates for single vehicle crashes in the modern SUV fleet (corresponding to NCAP rollover testing model years) and the impact of electronic stability control (ESC) and lowered center of gravity. We looked at 2001-2006 NASS-GES data on a probability sample of 3,331 SUVs involved in single vehicle crashes, weighted to represent 324,149 crashes in the study population. Static Stability Factor (SSF) information from NCAP testing and ESC presence (from IIHS) were also incorporated. 20.2% of these SUVs were involved a rollover, which decreased by more than half from model year 2001 (25.3%) through 2006 (11.5%). Nearly 9% had ESC as a standard feature, including 47% in model year 2006. The majority of the late model year decline in rollover rates can be attributed to ESC presence and higher SSF. Rollover was two-thirds less likely (adjusted OR=0.33, 95% CI=0.20-0.55) in SUVs with ESC as a standard feature versus those known not to have ESC. Those SUVs with SSF > or = 1.20 were significantly less likely to rollover (adjusted OR=0.31, 95% CI=0.20-0.48). Additional significant predictors of rollover included SUV size, driver age and alcohol use. Our study builds on the previous work of NHTSA, IIHS, and others with regard to rollover risk by looking at an even wider array of late model year SUVs.