The project examined the effects of the national maximum speed limit change on vehicular speeds and safety on 1200 miles of rural interstate highways in the state of Illinois, where the increase from 55 to 65 mph occurred in May of 1987. The speed limit increase does not apply to trucks. Analyses were made of speed data from four individual speed monitoring sites, and the aggregate of 15 sites, on rural interstate roads. The results indicate that there was an increase in the 85th percentile speed of passenger vehicles, on the order of four, or five, miles per hour, correlated with the change in the law. The frequency of all accidents increased on the order of 14 percent, in correlation with the law change. However, the same evidence could not be found for increases in either the frequency of serious accidents, or the accident rate. Furthermore, there was no strong evidence that speed differentials between trucks and cars were affected, or the car-truck accident experience changed.
Safety Impact of the 65 mph Speed Limit: A Time Series Analysis
1989
132 pages
Report
No indication
English
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