Recently, reports in both the popular and the scientific literature have questioned the safety and efficacy of air bags in passenger cars. Air bags were introduced in the 1960s and were created to reduce injury associated with frontal impacts. Since 1991, and in response to a US congressional mandate, air bags have been required on the driver side of most passenger cars and of light trucks and vans. As a result, air bags are now widely used, standard equipment on most passenger cars, light trucks, and minivans. From the time that air bags were introduced through early 2000, 152 deaths have been attributed to air bag deployment in low-severity crashes, and 58 decedents were drivers (1). These deaths have raised questions about air bag safety and efficacy. Despite concerns, the public perceives air bags as an effective and important automobile safety component (2).
Previous reports have estimated the mortality reduction attributable to air bags for drivers (3, 4) and for front-seat passengers (5). Estimates for drivers range from 24 to 28 percent (4, 5) and are 18 percent (5) for front-seat passengers. Although all studies have documented a benefit, measurement of the joint effect of air bags and seat belts after adjustment for confounding effects has remained difficult. Thus, we undertook a matched case-control study to measure the mortality reduction associated with air bag deployment and seat belt use for drivers involved in head-on passenger car collisions, after adjusting for potential confounders. We hypothesized that using either an air bag or a seat belt would significantly reduce mortality and that using seat belts in combination with air bags would provide a synergistic mortality reduction on the multiplicative scale greater than expected with either restraint system alone.
MATERIALS AND METHODS