NS749: Evaluation of Driver Speeds After Implementation of Speed Limit Reduction on Urban Streets
Problem and objectives
In 2019, Minnesota Legislature passed a law which reduced the barriers for cities to systematically reduce speed limits. In the City of St. Louis Park, traffic speeds were collected in advance of urban speed limit reductions (2021). In 2022, speed data was collected on streets where the speed limit was reduced and where the speed limit was unchanged with modest reductions noted. Theoretically, driver behavior is habitual, and it is anticipated that greater reductions will be experienced over time suggesting repeat traffic speed monitoring and assessment in three to five years after implementation (2025 to 2027). Many advocates persistently state that lowering speed limits will result in lower operating speeds, if just given enough time for a cultural shift on roadways. This study would follow up on those impacts. The first research found little to no impact with the lowering of speed limits. This study would examine if those changes occurred over a longer period (2-4 years later).
The goal of this research is to follow up on the earlier research, survey which Minnesota agencies have lowered speed limits, gather data on what changes have been seen (measured and anecdotal), where needed, collect “after” speed data, analyze and identify the best practices answering some of the questions posed by local agencies:
- Who has changed speed limits and who has considered?
- What is the effectiveness of these implementations on driver speed over a long timeframe?
- What other countermeasures have been implemented along with speed limit reductions? (Support with communication? Enforcement? Changes to roadway? Other?)
From these questions, this research will ascertain how effective speed limit reductions are, with and without accompanying treatments. To answer these questions, the following will be conducted:
- Review/synthesize current best practice and previous research on speed limit reductions.
- Survey MN agencies to identify places where speed limits have been changed, with follow-up interviews that would develop case studies.
- Collect any measured speed data from agencies that changed speed limits; ideally building a data set with data from three to five years after implementation.
- In cases where speed limits have been changed but “after” speed data has not been collected, facilitate collection of “after” speed data.
- Review and analyze the research data to determine any significant changes due to speed reductions.
- Assess potential changes to driver behavior with the various collected data sources.
Suggested deliverables
- Develop interim study/research (survey and follow-up interview) to understand which agencies have reduced speed limits and how it was implemented.
- Report on agencies that consider changing speed limits but didn’t and why.
- Report on how changing speed limits has affected actual driver’s speed and include recommendations.
The 2024 legislature requested a review of the validity of the establishment of speed limits statewide, due in March 2025. It was determined that the legislative request and this research project are unique ideas on differing timelines for completion and that this solicitation should move forward free of the legislative request.
Previous research
- Guidelines for Determining Speed Limits on Municipal Roadways
- Impact of Speed Limit Changes on Urban Streets
- TRS: Setting School Zone Speed Limits
- Speed Limit Guidance for Municipal Roadways
Possible members for technical advisory panel
- Sara Buermann, Wright County
- Vic Lund, St. Louis County
- Dave Kramer, Winona County
- Brian Sorenson, MnDOT
- Tony Winiecki, Scott County
- Nate Drews, MnDOT TE
- Max Moreland, MnDOT TE
- Randy Newton, St. Paul
- Mark Vizecky, MnDOT
- Additional city reps (metro and Greater MN)
Expected benefits
The numbers 1 and 2 indicate whether the source of the benefit measurement is from:
- A specific research task in your project that supports measuring this particular benefit, or
- Implementation of the research findings (anticipating positive results)
- Safety: For those communities with both existing and planned follow-up, data from this work will report on how driver speeds have changed since posting reduced speed limits. (1)
- Decrease Engineering/Administrative Cost: Identify tools for practitioners to use to guide posted speed limits (2)
- Operation and Maintenance Savings: Help agencies identify best practices for posted speed limits. (2)