Surveys have shown that raising the speed limit from 55 mph to 65 mph produces higher average speeds and a larger percentage of vehicles travelling at very high speeds. As a consequence of the 65 mph speed limit, fatalities on rural interstates have increased 20-30%. This paper describes a study in which information on speeds in various states was obtained by measuring vehicle speeds on rural interstate highways in 6 states that have retained 55 mph limits and 5 adjacent states with 65 mph limits. Details of the data collection and analysis are summarised. A summary of free-flowing vehicle speeds for passenger cars and tractor-semitrailers and the percentage of vehicles exceeding 65, 70 and 75 mph on the studied rural interstate highways in each state is tabulated. The results showed clearly, that the proportions of vehicles traveling at high speed are substantially lower in states with 55 mph speed limits than in states with 65 mph speed limits. The details of the study results are discussed. (A)
Abstract