If you think you don’t need to wear your seat belt because your car has an airbag, think again! Researchers estimate that airbags reduce the risk of driver death in a car accident by about 10% to 14%. That’s not much protection, and research recently published in BMJ (formerly the British Medical Journal ) suggests that airbags offer drivers even less protection than that. But most importantly, the BMJ study suggests that seat belts offer far better protection than airbags in a car accident.

About the study

Researchers at the University of Washington in Seattle searched the U.S. National Highway Traffic Safety Administration’s database for all passenger vehicle crashes between 1990 and 2000. They selected 51,031 vehicles with driver-passenger pairs in which the passenger was in the right front seat and the driver, passenger, or both died as a result of the accident. All passengers were age 16 or older. In selecting the driver-passenger pairs, the researchers excluded 8090 of them due to incomplete vehicle data, passenger age information, or airbag and seat belt data.

The database included information about:

  • Airbags (driver side, passenger side, or both)
  • Seat belt use for drivers and passengers
  • Vehicle type
  • Vehicle speed
  • Direction and location of impact
  • Whether the driver, passenger, or both died within 30 days as a result of the accident

The researchers used sophisticated statistical analysis techniques to estimate the risk of death for drivers in cars with airbags and drivers in cars without them, using passengers in the same vehicle as a comparison group. They also calculated the risk of death for belted and unbelted drivers.

In calculating the statistics, the researchers accounted for differences in age, seat position, vehicle speed, local speed limit, vehicle type, and direction/location of impact. They found little evidence that the associations of airbags and seat belts with risk of death were affected by these factors.

The findings

Drivers of cars with airbags were 8% less likely to die than those who drove cars without airbags, regardless of whether they wore a seatbelt or not. More importantly, drivers wearing seat belts were 65% less likely to die than drivers not wearing seat belts, regardless of whether the car had an airbag. Drivers who wore a seatbelt and had an airbag were 68% less likely to die than those who were unbelted without an airbag.

Although these results are interesting, there are some limitations to this study. First, information in the database regarding seat belt use was based on reports of police, rescue workers, and surviving occupants. It’s conceivable that some surviving occupants may have lied about being belted to avoid fines for not wearing their seat belts. Second, a full 15% of eligible driver-passenger pairs were excluded due to missing data. The strength of these findings could be weakened if these pairs differed significantly from those who were included in the analysis.

How does this affect you?

Does this mean airbags are worthless? Not necessarily. But this study does add to mounting evidence that seat belts provide far more protection in a car crash than airbags do. The most important message you should take away from this study is that an airbag is NOT a substitute for your seat belt.