Arizona's experience with the 65-mph speed limit is presented in terms of driver behavior and accident experience. The speed limit on Arizona's rural interstate was raised to 65 mph on April 15, 1987. Driver behavior is presented in terms of the speeds at which motorists actually drive on the rural interstate. Before and after data are presented from the last quarter of 1983 through the first quarter of 1988. Vehicle speeds increased by only about 3 mph or less during the four quarters following the speed limit increase. A 5-year history of interstate accident data-from 1983 through spring 1988-is presented that provides a before-and-after comparison. Information on total accidents, fatal accidents, and injuries is presented. Accident rate information is presented to account for the effect of increasing vehicle-miles of travel. Accident data on the urban interstate are presented for comparison purposes.

Speed limits on rural highways has been a topic of intense interest to both the general public and the traffic engineering and enforcement communities during the past 15 years. The national maximum speed limit of 55 mph was enacted in 1974 and remains in effect on most of the nation's rural highway mileage. In April 1987, the United States Congress passed legislation allowing individual states to increase the speed limit on the rural interstate system to 65 mph. To date, about 40 states have chosen to increase the speed limit on the rural interstate.