“NHTSA recorded 238 airbag-related deaths between 1990 and 2002,” Meyer said. “They occurred at very low speeds, with injuries impossible to link to anything else. But it seems likely that airbags also cause deaths at high speeds when deaths are attributed to impact.”

Airbags have been required for drivers and front-seat passengers in all cars since the 1998 model year in the United States.

It’s hard to know for sure what would have happened in a crash without an airbag, Meyer said, “but by comparing patterns in data you can compare different situations and derive disturbing conclusions.”

Meyer used a dataset that contains random samples of all accidents to analyze the role of airbags in all accidents. Earlier studies used a subset of accidents in which at least one person was killed.

By looking only at more dangerous, high-speed collisions, Meyer was able to reproduce previous results showing the beneficial effect of airbags. However, when she examined a random sample of all accidents, airbags were related to higher probabilities of death.

“Making airbags ubiquitous, then verifying their effectiveness using only fatal highway crashes is like making everyone get radiation treatment, then estimating lives saved by looking only at cancer patients,” she said. “Overall, there will be more deaths if everyone is given radiation, but in the cancer subset, radiation will be effective.”

Meyer’s findings directly contradict assertions about airbag safety on the NHTSA Web site.

“We must get it right, now,” she said, “because in a few years there will be virtually no cars on the road without airbags, and making comparisons will be impossible.”

For more information, contact Mary C. Meyer at wfinlay@uga.edu.