Seatbelts are the lifesavers in your car

New Orleans Times-Picayune editorial "Seatbelts are the lifesavers in your car" (September 9th, 2010) speaks positively of seat belts.  While they have undoubtedly saved lives, they have also undoubtedly cost them through the externalities their cost-shifting generates.

More Louisianians buckled up this year compared to last, according to the Louisiana Highway Safety Commission, but the New Orleans area actually saw a 1.1 percent decline in the percentage of people using seat belts.

Even with the statewide increase for drivers and front-seat passengers, which went from 74.5 percent to 75.9 percent, Louisiana still lags behind the nationwide usage rate of 83 percent.

That's discouraging, because buckling up is a simple and easy thing to do, and it's a proven life-saver.

The most interesting economic concept when it comes to seat belts and safety regulation is the "Peltzman Effect", as Sam Peltzman discusses in his 1975 Journal of Political Economy article "The Effects of Automobile Safety Regulation" (gated).  Below, we reproduce his diagram graphically (click to enlarge).  What the diagram indicates is that risky driving gives us something we enjoy--for example getting to our destination more rapidly.  Our first bit of risky driving is particularly beneficial--perhaps when we are in a hurry.  As we increase our risky driving, the marginal benefit decreases.  This is represented by the downward sloping red line. Under a regime with no seat belts, we end up at an equilibrium represented by point A on the risky driving schedule.  Under a regime with seat belts, we end up at an equilibrium represented by point B.  As driving becomes safer, we drive more riskily.

This, in turn may cause more pedestrian deaths, whose cost is presumably not fully borne by drivers.  Below, we graphically depict the relationship between risky driving and pedestrian deaths (click to enlarge).  We can see that pedestrian deaths rise as we go from point A and B.  (Point C will be discussed below).

As a thought exercise, famous among Austrian economists, is what would occur if instead of seatbelts or airbags, we installed a large spike in driving wheels, faced toward the driver a driving wheel looking similar to this:

In this case, we would have the following relationship between risky driving probability of death to driver (click to enlarge):

If this is the case, we end up at point C on the diagram above (again, click to enlarge).

This article serves to demonstrate a few concepts.  First, a common refrain on Corrections: when we reduce the cost of behavior that has benefits and costs, we increase the partaking of that behavior.  Second, when that behavior has externalities, as it does with driving, we may actually foist the cost of risky driving onto pedestrians rather than consumers.