Speed limits

This cover letter accompanied the 2016 Report on the Evaluation of Certain Highway Speed Limits.

This report is issued to comply with 2014 Minnesota Law Chapter 312--H.F. 3172, Sec. 36. The commissioner of transportation shall perform engineering and traffic investigations on trunk highway segments that are two-lane, two-way roadways with a posted speed limit of 55 miles per hour. On determining upon the basis of the investigation that the 55 miles per hour speed limit can be reasonably and safely increased under the conditions found to exist on any of the trunk highway segments examined, the commissioner may designate an increased limit applicable to those segments and erect appropriate signs designating the speed limit. The new speed limit shall be effective when the signs are erected. Of all the roadways to be studied under this section, approximately one-fifth must be subject to investigation each year until the statewide study is complete in 2019.

This cover letter accompanied the 2015 Report on the Evaluation of Certain Highway Speed Limits.

This report is issued to comply with 2014 Minnesota Law Chapter 312--H.F. 3172, Sec. 36. The commissioner of transportation shall perform engineering and traffic investigations on trunk highway segments that are two-lane, two-way roadways with a posted speed limit of 55 miles per hour. On determining upon the basis of the investigation that the 55 miles per hour speed limit can be reasonably and safely increased under the conditions found to exist on any of the trunk highway segments examined, the commissioner may designate an increased limit applicable to those segments and erect appropriate signs designating the speed limit. The new speed limit shall be effective when the signs are erected. Of all the roadways to be studied under this section, approximately one-fifth must be subject to investigation each year until the statewide study is complete in 2019.

This cover letter accompanied the 2014 Report on the Evaluation of Certain Highway Speed Limits.

This report is issued to comply with 2014 Minnesota Law Chapter 312--H.F. 3172, Sec. 36. The commissioner of transportation shall perform engineering and traffic investigations on trunk highway segments that are two-lane, two-way roadways with a posted speed limit of 55 miles per hour. On determining upon the basis of the investigation that the 55 miles per hour speed limit can be reasonably and safely increased under the conditions found to exist on any of the trunk highway segments examined, the commissioner may designate an increased limit applicable to those segments and erect appropriate signs designating the speed limit. The new speed limit shall be effective when the signs are erected. Of all the roadways to be studied under this section, approximately one-fifth must be subject to investigation each year until the statewide study is complete in 2019.

The Minnesota Speed Management Program (MSMP), a cooperative project between the Minnesota Department of Transportation and the Minnesota Department of Public Safety, was developed within the framework of the Minnesota Comprehensive Highway Safety Plan. The overall goal was to reduce the number of fatal and lifechanging crashes on Minnesota highways. The MSMP involved a speed limit adjustment—on 850 miles of Minnesota’s 55 mph highways the speed limit was increased to 60 mph. It involved increased speed enforcement—by State Patrol, county sheriffs, and local law enforcement—on selected highways. There were four waves of Enhanced Enforcement (one of six weeks, three of eight weeks) each followed by four weeks of Regular Enforcement. The MSMP involved extensive public education, organized by the Office of Traffic Safety, with approximately 10,000 public service messages presented on the radio. Two evaluation efforts were conducted. The University of Minnesota compared travel speed data and crash data obtained during the MSMP with historical data. Throughout the MSMP, there were decreases in the number of drivers traveling at least 10 mph above the speed limits—decreases of -28.7% on 2-Lane/2-Way Highways; -28.7% on 4-Lane Divided Highways; -42.9% on Rural Freeways; and -11.2% mph on Urban Freeways. The University’s evaluation also showed there were reductions in the numbers of fatal and life-changing crashes during the MSMP. MarketLine Research conducted the second evaluation, using telephone surveys, and found nine in ten drivers support the speed limit increase from 55 mph to 60 mph in both Metro and Greater Minnesota. The MSMP, in concert with other efforts that are part of the Minnesota Comprehensive Highway Safety Plan, resulted in reductions in the number of speeders on Minnesota Highways and reductions in the number of fatal and lifechanging crashes—making Minnesota’s roads safer.

The objective of this study was to evaluate the safety impacts of increasing the speed limit from 55 mph to 60 mph on two-lane, two-way state highway road segments in Minnesota. An empirical Bayes (EB) before-after analysis was used to estimate crash modification factors (CMFs) for both segments and intersections. The segment analysis showed an 8 percent reduction in total crashes that was statistically significant, alongside a significant 15 percent increase in combined fatal, serious injury, and minor injury (KAB) injury crashes. The range of most of the segment CMFs hovered close to 1. The intersection analysis was split into two groups (all traffic control types and thru-stop control only). The aggregate CMFs for all intersections within these two groups showed, on average, between a 10% and 20% statistically significant reduction in total and injury crashes. Analysis was also performed on four subgroups (3- and 4-leg, lighting/no lighting) within the two main intersection groups. Disaggregating the intersections into further groups led to smaller sample sizes that led to higher standard errors showing a widespread range of CMFs around 1 for the individual crash types and severities. The aggregate estimated crash safety effects (for total and injury crashes) for combined segments and intersection sites showed a reduction in total crashes but an increase in the KAB injury crashes.

This Implementation Summary relates to Report 2023RIC07, published in April 2023.

This Technical Summary pertains to Report 2023-22, “Impact of Speed Limit Changes on Urban Streets,” published June 2023.