About the research
The objective of this research was to examine whether a significant change in accident rates could be detected following implementation of the 65 mph speed limit on rural interstate highways in Iowa. Applying time series analysis and controlling for general growth in vehicle miles traveled, an increase in fatal accidents was detected around the middle of 1987 on rural interstate highways. This leads to the conclusion that the increase in speed limit on Iowa’s rural interstate highways in May of 1987 has contributed to a rise in fatal accidents. However, a similar increase in major injury accidents was not found.