Methods for Setting Posted Speed Limits

Traditionally, Minnesota’s posted speed limits are determined using the Institute of Transportation Engineers (ITE) methodology as well as other considerations. The ITE methodology uses field measurements to evaluate roadway segments for the speed at or below which 85 percent of free flowing vehicles are traveling. The Minnesota Department of Transportation (MnDOT) has observed that the ITE methodology often determines a higher operational speed for two-lane rural highways than MnDOT believes is warranted by other engineering and safety considerations. Further, MnDOT is being asked to justify posted limits of 55 mph when statutory limits for such roadways in Minnesota are 65 mph. Consequently, MnDOT would like to identify alternative methods used for determining posted speed limits that produce greater compliance by motorists. CTC & Associates conducted a literature search and contacted three state departments of transportation—Illinois, Texas and Washington—to help identify potential methods, focusing on the following areas: Equipment and sampling methods, including the use of 24-hour tube counts; Methods most effective for improving compliance with posted speed limits; Factors taken into account when setting speed limits, including land use, access points and other roadway users; and Determining whether differing methods are more effective for urban than for rural roadways. CTC & Associates identified research related to the following key topic areas: National Resources; Consultation with State Practitioners; State Practices; International Practices; and Related Research.


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  • Accession Number: 01601711
  • Record Type: Publication
  • Created Date: May 31 2016 1:18PM