The issue of reducing speed limits to increase public safety is an emotional, political, and controversial topic that has been debated by safety advocates, engineers, politicians, transportation officials, and the public for many years. A statutory change in 2019 put a spotlight on the topic, requiring a deeper look into how speed limits are established and the effectiveness that lowering speed limits has on reducing vehicle traveling speeds, as well as the impacts on pedestrian and bicycle traffic.
In a recent project from the Local Road Research Board’s Research Implementation Committee, researchers developed a quick reference guide that provides an explanation of the updated statute and describes best practices for setting speeds on local roads.
Background
MN Statute 169.14 was passed in 1937, establishing consistent statewide speed limits for alleys and streets in urban districts, local roads, expressways, and interstate highways.
Statutory speed limits on most roadways include:
- 10 mph in alleys.
- 30 mph on streets in urban districts (can be reduced to 25 mph if a speed zone is adopted and the roadway is property signed).
- 55 mph on other roads.
- 65 mph on expressways.
- 65 mph on urban interstate highways.
- 70 mph on rural interstate highways.
If state or local authorities believed that the statutory limits would not be effective, the statute allowed for speed zones (non-statutory regulatory speed limits) to be established. This required that a speed study be conducted by MnDOT, and that the transportation commissioner approved the change.
The statute was updated in August 2019 by the Minnesota State Legislature. The change gave cities the authority to establish speed limits for streets under their jurisdiction without having MnDOT conduct a speed study, and without approval by the transportation commissioner provided that:
- Speed limits are implemented in a consistent and understandable manner.
- The city erects appropriate signs to display the speed limit.
- The city develops procedures to set speed limits based on the city’s safety, engineering, and traffic analysis considering national urban speed limit guidance and studies, local traffic crashes, and methods to effectively communicate the change to the public.
What Does This Mean for Municipalities?
The revised statute maintains a 30-mph speed limit in urban districts with the ability to reduce the limit to 25 mph with adoption of a speed zone and proper signage. The change simply affords communities the opportunity to change speed limits on roads under their jurisdiction. This authority is granted only to city streets and does not apply to town roads, county highways, or trunk highways located in the city.
What Was Our Goal?
This project sought to understand the effectiveness of speed limit changes and outline a process for agencies to follow when deciding to make a change.
“Our goal was to provide a documented process that can be used by local agencies considering a speed limit change. It puts the information they need in one easy-to-use reference guide. It also includes essential history and background information, and offers alternative pedestrian and bicycle safety strategies,” said Will Manchester, director of Public Works, City of Minnetonka and the project’s technical liaison.
What Did We Do?
An extensive literature review helped identify the extent of knowledge that exists among local agencies regarding establishing roadway speed limits and issues associated with changes. The experience of agencies that have navigated this process was utilized to create a summary document for use in developing the reference materials.
This guidance includes local and national studies on the effectiveness of speed limit changes. It also includes a compilation of case studies from Minnesota cities, and a facts/myths section that charts how speed limits affect speed and how speed and speed limits affect bicycle and pedestrian crashes.
The guidebook explains the recent statutory change and the consequence of the change to communities. It outlines a process that agencies can follow to conduct a corridor-specific speed limit study, set speeds, establish and implement a citywide speed limit, and develop signage.
What Did We Learn?
Data analyzed does not suggest that lowering a speed limit will result in lower travel speeds. Effectively lowering vehicle speeds requires a combination of physical, operational, and regulatory measures to be successful.
Whenever possible local agencies should implement proven alternative strategies and modify the roadway environment to reduce travel speeds. Effective strategies include adding sidewalks, median crossing/refuge islands and crosswalk lighting and beacon systems. Road diets or reallocation of roadway lanes can also be employed to add features like bike lanes or pedestrian refuge islands on existing roads.
The guidance also recommends conducting a robust public involvement campaign prior to implementing a citywide reduction in speed limits. This step is crucial to separate data from perception and determine if a community would like to consider a change, as well as if residents and elected officials understand the likelihood of achieving a reduction in travel speeds.
Crossroads 