The Evolution and Devolution of Speed Limit Law and the Effect on Fatality Rates

Abstract

The three most recent decades provide an outstanding opportunity to study the changing federalist landscape concerning the regulation of speed on the nation's highways. Speed limits were the province of the states until the 1970s when, in an effort to save energy, the central government nationalized the maximum speed at 55 miles per hour. The national standard remained until the 1980s, when a partial devolution transferred some power to set speed limits back to the individual states. At that time, states could increase the maximum speed to 65 miles per hour on (at fewest) four-lane, controlled access highways in low population density areas. Some states elected to loosen the limits within their borders, while others did not, citing concerns of highway safety as paramount. The 1990s saw the complete devolution of speed limit control to the states, when Congress returned to the states unlimited control. States reacted differently in both of the two latter phases, providing a fruitful landscape for comparative analysis of the effects of the devolution of speed limit control.

The focus of this research is to examine which states raised the speed limits at the two stages of devolution, and what the subsequent effects were. I examine the issue of highway safety as a consequence of speed limit change, comparing states to elucidate differences to determine effects. Analysis of highway deaths per mile driven indicates that the nationalization of the 55 miles per hour contributed to an initial greater decline in the former than had been the trend, but the long-term decreasing trend pattern reemerged following the shock of the change in federal speed limit policy. Additionally, the speed limit devolution and resulting raising of speed limits in certain states did not lead to a statistically significant rise in fatalities per miles driven. Automobile safety features and enforcement emerge as important factors in increasing highway safety; speed limits are far less important.