Influence of the unbelted rear-seat passenger on driver mortality: "The backseat bullet"

This study examined whether unrestrained left rear-seat passengers increase the risk of death of belted drivers involved in serious crashes with at least one fatality. The information from every fatal crash in the United States between 1995 and 2001 was analyzed. Variables such as point of impact, restraint use, seat position, vehicle type, occupant age, gender, and injury severity were extracted from the Fatality Analysis Reporting System. The odds of death for a belted driver seated directly in front of an unrestrained passenger in a serious head-on crash was 2.27 times higher (95% confidence interval [CI] = 1.94 to 2.66) than if seated in front of a restrained passenger. In contrast, a belted driver seated in front of an unrestrained passenger in a driver-side lateral-impact crash had no increase in mortality over a driver with a restrained rear-seat passenger (odds ratio, 0.8; 95% CI = 0.6 to 1.06). Logistic regression showed that passenger restraint, point of impact, vehicle type, passenger age, and driver age had a statistically significant influence on the outcome (death) of belted drivers. Adjusting for confounders (other than point of impact), the odds of fatality for a belted driver in a head-on crash was 2.28 times greater (95% CI = 1.93 to 2.7) with an unbelted rear-seat passenger. The unbelted rear-seat passenger also had an increased risk of death (odds ratio, 2.71; 95% CI = 2.44 to 3.01) when compared with restrained rear-seat passengers. Unrestrained rear-seat passengers place themselves and their driver at great risk of fatal injury when involved in a crash.