As concerns about fuel availability and costs faded, however, speeds began to gradually climb on U.S. highways. By the mid-1980s, a substantial majority of vehicles on rural interstates were exceeding 55 mph. In response to claims that the 55 mph limit had made the United States a nation of law breakers and assertions that deaths and injuries would not increase because people already were traveling at the speeds at which they felt comfortable, Congress allowed states to increase speed limits on rural interstates to 65 mph in 1987. The National Highway System Designation Act of 1995 repealed the maximum speed limit, allowing states to set their own limits for the first time since 1974. Many states quickly moved to raise speed limits on both rural and urban interstates and limited access roads.
Many drivers tend to drive somewhat faster than posted speed limits, no matter what the limits are.
Although people often opt to travel somewhat faster than the posted limit, they do not completely ignore it but choose a speed they perceive as unlikely to result in a ticket. The more important speed-related safety issue on freeways involves the proportion of vehicles traveling at very high speeds, not the proportion violating the speed limit. The Institute's frequent monitoring of free-flowing travel speeds on interstate highways posted at 55 mph and speeds on roads with 65 and 75 mph limits shows that, in general, higher speed limits lead to greater proportions of cars traveling at very high speeds. For example, in New Mexico, which raised its limits to 65 mph on rural interstates in 1987, the proportion of motorists exceeding 70 mph grew from 5 percent shortly after speed limits were raised to 36 percent in 1993. After speed limits were further increased to 75 mph in 1996, more than 42 percent of motorists exceeded 75 mph.