To assess the efficacy of occupant protection systems, the authors measured the mortality reduction associated with air bag deployment and seat belt use for drivers involved in head-on passenger car collisions in the United States. They used a matched case-control design of all head-on collisions involving two passenger cars reported to the Fatality Analysis Reporting System in 1992-1997, and driver mortality differences between the paired crash vehicles for air bag deployment and seat belt use were measured with matched-pair odds ratios. Conditional logistic regression was used to adjust for multiple effects. There were 9,859 head-on collisions involving 19,718 passenger cars and drivers. Air bag deployment reduced mortality 63% (crude odds ratio (OR) = 0.37, 95% confidence interval (CI): 0.32, 0.42), while lap-shoulder belt use reduced mortality 72% (OR = 0.28, 95% CI: 0.25, 0.31). In a conditional logistic model that adjusted for vehicle (rollover, weight, age) and driver (age, sex) factors, air bags (OR = 0.71, 95% CI: 0.58, 0.87) and any combination of seat belts (OR = 0.25, 95% CI: 0.22, 0.29) were both associated with reduced mortality. Combined air bag and seat belt use reduced mortality by more than 80% (OR = 0.18, 95% CI: 0.13, 0.25). Thus, this study confirms the independent effect of air bags and seat belts in reducing mortality. (A)
Abstract