About speed limits
Why we have speed limits
A uniform speed of vehicles in a traffic flow results in the safest operation. Posted speed limits can help keep the traffic flowing smoothly provided the majority of drivers find the speed limits reasonable. This is called “voluntary compliance.” To best achieve voluntary compliance, the speed limits must be consistent throughout the state. Speed limits also give motorist an idea of a reasonable speed to drive in an unfamiliar location.
When established properly, speed limits are essential for law enforcement to identify excessive speeds and curb unreasonable behavior.
How we set speed limits
Minn. Statute 169.14 establishes statutory speed limits on most typical roadways under ideal conditions. Unless otherwise posted:
- 10 mph in alleys
- 30 mph on streets in urban districts
- 55 mph on other roads
- 65 mph on expressways
- 65 mph on urban interstate highways
- 70 mph on rural interstate highways
Based on a traffic study
All other speed limits are set by the Commissioner of Transportation based upon an engineering and traffic investigation. These factors are considered:
- Road type and condition
- Location and type of access points (intersections, entrances, pedestrian access, etc.)
- Sufficient length of roadway (1/4 mile minimum)
- Existing traffic control devices (signs, signals, etc.)
- Crash history, traffic volume, sight distances (curve, hill, etc.)
- Travel speed samples
- Test drive results speed study
Types of speed limits
A black and white sign shows the maximum speed that a motorist may travel under ideal conditions. It can be a statutory value or else it must be authorized by the Commissioner of Transportation.
A black and yellow speed sign is used with a hazard warning sign to advise motorists of a comfortable speed to navigate certain situations. For instance, when traveling on a winding road, the curve warning sign would be used with an advisory speed sign.
Ensuring the safety of children who cross public streets near schools is the responsibility of drivers, parents, school officials and road authorities. When combined with proven safety strategies, school zone speed limits can be effective.
MnDOT’s Safe Routes to School program has more information on school zone safety.
MnDOT outlines the guidelines, proper layouts and procedures for implementing various speed limit types to be used in work zones. Get more information about work zone safety.
Speed and safety
Lower speed limits don't reduce speeds
Studies show that there is little change in speed patterns after posting a lower speed limit. Drivers are much more influenced by changes to the roadway, its environment and conditions.
Lower speed limits don't reduce crash frequency
Lower speed limits are often viewed as a quick fix to traffic safety, but this is not the case. Crashes are most often the result of other factors. In many cases, posting a lower speed limit creates a greater speed variance between the slowest and fastest-moving vehicles. This speed variance, also called “speed differential,” can contribute to crashes and make the roadway less safe.
State highways, U.S. highways, and interstates
Contact the district traffic engineer at your MnDOT district office.
County roads and county highways
Contact the appropriate Minnesota county.
Contact the appropriate Minnesota city.