The massive safety effects of vehicle regulations -- and seat belt regulation in particular

by Brian Wolfman

We've told you before about the huge reductions in on-the-road deaths caused by various forms of vehicle safety regulations. And we heard just yesterday about the latest vehicle safety rule-in-the-making--not many years away--being pushed by the National Highway Traffic Safety Administration (NHSTA): cars talking to each other to avoid crashes.

But seat belts are the single most effective traffic safety device for preventing death and injury, according to NHTSA. Wearing a seat belt can reduce the risk of crash injuries by 50 percent. Seat belts saved more than 75,000 lives from 2004 to 2008. Forty-two percent of passenger vehicle occupants killed in 2007 were unbelted. A 2009 NHTSA study estimates that more than 1,600 lives could be saved and 22,000 injuries prevented if seat belt use was 90 percent in every state.

Seat belt use didn't happen by chance. it took regulation and a large publicity campaign (largely taxpayer funded) to get where we are. It wasn't until 1968 that federal law required all new vehicles (except buses) to be equipped with seat belts. And it wasn't until 1984 that a single state (New York) required their use. Now, all but one state (New Hampshire) requires their use. One key determinant of seat belt use is whether a state is a "primary law state" (where a vehicle occupant can be pulled over solely for not using a seat belt) or a "secondary law state" (where a vehicle occupant can be ticketed for not using a seat beat, but only if the car is pulled over for some other infraction). NHTSA just issued its 2013 seat belt use survey, which shows that in "primary" states seat-belt use is at 91%, while in "secondary" states use is only at 80%. And since states began enacting "primary" laws, seat belt use has increased dramatically. Between 1995 and 2013 alone, use has gone from 60% to 87%.

There are many statistical studies on the effects of seat belt use on traffic-related deaths and driving behavior. This one from about 10 years ago by economists Alma Cohen and Liran Einav may be interesting to our more mathametically inclined readers.