The National Highway Traffic Safety Administration (NHTSA) estimates that airbags installed in automobiles have saved some 10,000 lives as of January 2004. A just-released study by a statistician at the University of Georgia, however, casts doubt on that assertion.
In fact, said UGA statistics professor Mary C. Meyer, a new analysis of existing data indicates that, controlling for other factors, airbags are actually associated with slightly increased probability of death in accidents, according to a news release from the University of Georgia Public Affairs Office.
The new analysis directly contradicts earlier studies about the effectiveness of airbags, which have been required for drivers and front-seat passengers in all cars since the 1998 model year in the United States.
While the value of airbags seems dubious in the new study, the value of seatbelts is not. The analysis found that proper use of a seatbelt reduces the odds of death by 67 percent for any given speed category and airbag availability. Airbags, however, cause no statistical difference in car-crash deaths, except for occupants without seatbelts at low speeds, where the odds of death are estimated to be more than four times higher with an airbag than without.
The reason earlier studies have found that airbags save lives is that they used only a special subset of the available data, said Meyer. The Fatality Analysis and Reporting System (FARS) is a high-quality compilation of information about every highway accident for which a death occurred. The Crashworthiness Data System (CDS) is another high-quality dataset, containing random samples of all accidents. The previous studies used FARS, and Meyer’s study used CDS.
“When we look at the random sample of all accidents, we find that airbags are associated with increased risk of death,” she said, “and this increase is due to more deaths with airbags in low-speed crashes and no seatbelts. However, if we limit the dataset to include only collisions in which a fatality occurred, we get a significantly reduced risk of death due to airbags.”