Safety Impact of the Increased 65 MPH Speed Limit on Iowa Rural Interstates

Project Details
STATUS

Completed

PROJECT NUMBER

UIA-16-C

START DATE

07/01/94

END DATE

07/01/94

RESEARCH CENTERS InTrans, CTRE, MTC
SPONSORS

Iowa Department of Transportation
Midwest Transportation Center

Researchers
Principal Investigator
Johannes Ledolter

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.

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