Factors affecting injury severity of single-vehicle rollover crashes in the United States

Objective: This study investigated the confounding effects of factors on injury outcomes for all occupants in fatal single-vehicle crashes that involved a rollover event. Method: A generalized ordered logit model was used to investigate the role of roadway attributes, environmental factors, driver characteristics, and vehicle features in injury severity outcomes for occupants. Five years of single-vehicle rollover crash data for the United States were studied. Results: Results showed that the likelihood of serious and fatal injuries increases in rollover crashes with partial or complete ejection of the occupant, no seat belt use, speeding, higher posted speed limits, roadside and median rollovers, undulating terrain, blacktop road surface, and rural roads. We also found that evening, weekdays, previous driver crash, careless or inattentive driving, driver-passenger engagement, aggressive driving, and vehicle type affect injury severity. The deployment of airbags was associated with fewer serious and fatal injuries. Regional differences were found for injury severity outcomes in rollover crashes. Conclusions: The study provides valuable insight for reducing injury severity in single-vehicle crashes where a rollover occurs. Several proven countermeasures may prevent rollovers or reduce injury severity. These strategies include increasing seatbelt use, posting lower speed limits and installing speed enforcement cameras in high-risk areas, flattening roadside embankments, and promoting in-vehicle stability enhancement systems such as electronic stability control and rollover-activated side curtain airbags.