Carpe Diem

Automobile Safety: Seatbelts Cause Accidents

Do automobile safety features like seat belts and air bags really save lives? Maybe not.

Economist Sam Peltzman argues that manadatory safety features like seat belts and air bags reduce the probability of death or serious injury to the driver in an accident, but the increased feeling of safety from seat belts or airbags would actually cause drivers to drive slightly more recklessly, which would increase the number of accidents.

Think about it: Who gets stuck in the mud or snow more often – drivers in 4-wheel drive vehicles or standard 2-wheel drive vehicles? Probably drivers in 4-wheel drive vehicles – feeling “empowered” by the 4-wheel drive feature, they take more risks, and get stuck more often.

Likewise, seatbelts and airbags make drivers feel slightly more “empowered” with the increased safety and protection, and would drive slighlty more recklessly. Drivers would be more likely to survive a serious accident with seatbelts and airbags, but the number of accidents would go up, so the net effect on overall deaths from car accidents could go up, down or stay the same. What does the empirical evidence show? According to Peltzman (from Russell Roberts on Cafe Hayek):

“Holding other factors constant that might change the number of accidents (and this is never easy but he did the best he could with the data at hand), Sam Peltzman found that mandatory seat belts did indeed cause more accidents. But this effect was roughly the same as the effect in the opposite direction, that accidents were less harmful. So the net number of fatalities of drivers was unaffected by the law. Sam found some evidence that the effect of the law might be to reduce driver fatalities. Unfortunately, because drivers were more reckless, there were more accidents involving pedestrians and cyclists. So their death rate due to cars increased. Total deaths were unchanged.”

Conclusions: 1) Incentive matters. 2) Mandatory safety requirements don’t necessarily increase overall saftey, because of conclusion #1.

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