DID THE 65-MPH SPEED LIMIT SAVE LIVES

In 1987, most states raised the speed limit from 55 to 65 mph on porti ons of their rural interstate highways. There was intense debate about the increase, and numerous evaluations were conducted afterwards. The se evaluations share a common problem: they only measure the local eff ects of the change. But the change must be judged by its system-wide e ffects. In particular, the new 65 mph limit allowed the state highway patrols to shift their resources from speed enforcement on the interst ates to other safety activities and other highways-a shift many highwa y patrol chiefs had argued for. If the chiefs were correct, the new al location of patrol resources should lead to a reduction in statewide f atality rates. Similarly, the chance to drive faster on the interstate s should attract drivers away from other, more dangerous roads, again generating system-wide consequences. This study measures these changes and obtains surprising results. We find that the 65 mph limit reduced statewide fatality rates by 3.4% to 5.1%, holding constant the effect s of long-term trend, driving exposure, seat belt laws, and economic f actors.