Public Policy

Mandatory Seat Belt laws

A recent paper in the May 2008 edition of the Journal of Health Economics by Carpentera and Stehr finds that mandatory seat belt laws save lives.

…we find consistent evidence that state mandatory seatbelt laws – particularly those permitting primary enforcement – significantly increased seatbelt use among high school age youths by 45–80%, primarily at the extensive margin. Unlike previous research for adults, however, we find evidence against the selective recruitment hypothesis: seatbelt laws had consistently larger effects on those most likely to be involved in traffic accidents (drinkers, alcohol-involved drivers). We also find that mandatory seatbelt laws significantly reduced traffic fatalities and serious injuries resulting from fatal crashes by 8 and 9%, respectively. Our results suggest that if all states had primary enforcement seatbelt laws then regular youth seatbelt use would be nearly universal and youth fatalities would fall by about 120 per year.

So should we implement mandatory seat belt laws? From the evidence in their paper, Carpentera and Stehr believe so. However, is this issue truly so clear cut?

One question is whether or not mandatory seat belt laws really caused increased seat belt use. Did the seat belt laws cause increased seat belt use or did increased seat belt use lead to the increased popularity and passage of a law?

This paper is important in that it quantifies the benefits of the mandatory seat belt laws, but does not quantify the costs. What is the cost of enforcement in terms of 1) time law enforcement must dedicate to seat belt policing instead of “real” police work? and 2) the cost to the justice system and work absences due to the adjudication or appeals process for seat belt violation, and 3) the violation of a person’s individual freedom to choose to not wear a seatbelt. In this case, there is no externality to not wearing a seat belt; the person harmed from not wearing a seat belt is that person themselves. A libertarian would be strictly against a mandatory seat belt law. Nevertheless, a compelling argument can be made that minors do not use an optimal decision-making process when deciding whether or not to wear a seat belt.

Do I support a mandatory seat belt law? No.

I believe that parents should help to convince their child to use seat belts and that it is possible that schools should educate children on the benefits of using a seat belt. However, using police resources to fine individuals who do not wear seat belts seems to be a waste of resources. If mandatory seat belt laws are not enforced, then this would free up police resources, but also would weaken the impact of mandatory seat belt laws.

Seat belt save lives. But I think parents and schools–not the government–are the best institutions to spread this message.