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prepared by Mn/DOT Office of Traffic, Security and Operations
September 1998

Index to the Brochure

What are the Legal Speed Limits?

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MN Statute 169.14 click here for Mn Statute Text

Minnesota's speed regulations are based on the same Basic Speed Law that is used in all 50 states: "No person shall drive a vehicle upon a highway at a speed greater than is reasonable or prudent having due regard for weather, visibility, the traffic on, and in no event at a speed which endangers the safety of persons or property." Speed laws are created for the protection of the public and the curbing of unreasonable behavior. To effectively enforce a law, the public must believe that the law is reasonable.

Statutory limits are based on the concept that uniform categories of highways can operate safely at certain preset maximum speeds under ideal conditions. Whether the speed limit is posted or unposted, drivers are required to reduce speed below these values for poor weather conditions, curves or hills and potential hazards such as pedestrians.

These are the most common statutory speeds:
	10 mph in alleys
	30 mph on all streets in urban districts
	70 mph on rural interstate highways	greater mn interstate and expressway speed limit map
	65 mph on urban interstate highways	metro area speed limit map
	65 mph on all expressways	metro area and greater mn speed limit map
	55 mph on all other roads

Whenever these statutory speed limits are not the correct value for a specific highway, the commissioner of transportation may authorize the posting of other regulatory speed limits.

How Does Mn/DOT Determine
the Regulatory Speed Limit?

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The commissioner of transportation sets regulatory speed limits on state and local roads based on a thorough engineering and traffic investigation.

These factors are considered:

• road type and surface (curve, hill, etc.)
• location and type of access points (intersections, entrances, etc.)
• sufficient length of roadway (1/4 mile minimum)
• existing traffic control devices (signs, signals, etc.)
• accident history
• traffic volume
• sight distances
• test drive results
• speed study

The most important part of the traffic investigation is the speed study. When choosing a speed, drivers take many roadway environment factors into consideration. Therefore, the speed that the majority of people consider prudent is an important value. Data is collected by performing radar checks at selected locations on the roadway under ideal driving conditions. A technical analysis is done on the results to determine the 85th percentile. This is the value indicating the speed at which most (85%) drivers are traveling under. Experience has shown that a posted speed limit near this value is the maximum safe and reasonable speed. Studies have shown that traveling much faster or slower than this value can increase your chance of being in a crash.

Engineering judgement is an important tool. The traffic investigator must use knowledge of nationally accepted principles combined with experience to assign the safe speed.

What are the Types of Speed Limits?

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	REGULATORY SPEED LIMIT SIGN
	This black and white sign shows the maximum speed that a motorist may travel under ideal conditions. It must be authorized by the commissioner of transportation. click for MnMUTCD specifications on size and sign installation

	ADVISORY SPEED SIGN
	This black and yellow speed sign is used to advise motorists of a comfortable speed to navigate certain situations. It is used with a warning sign. For instance, when traveling on a winding road, the curve warning sign would be used with an advisory speed sign. This sign may be posted by the local road authority on local roads. click for MnMUTCD specifications on size and sign installation

What are Special Types of Speed Zones?

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	SPEED LIMITS IN SCHOOL ZONES
	These can be established by the local authority on local roads in a school zone. This regulatory speed limit is in effect whenever children are present, such as before and after school or during recess. The school plate is black and yellow and the other signs are black and white. click for MnMUTCD specifications on size and sign installation

	SPEED LIMITS IN WORK ZONES
	Advisory speed limits are used to identify safe speeds for specific conditions within a work zone. These black and orange signs are always used with warning signs. The local road authority can post these plates in work zones on local roads. click for MnMUTCD specifications on size and sign installation
	Work zone speed limits are short term regulatory speed limits that are established for worker safety due to traffic in adjacent lanes. These speed limits range from 20 mph to 40 mph and can be posted by the local road authority in active work zones on local roads. The work zone plate is black and orange and the speed limit sign is black and white. click for MnMUTCD specifications on size and sign installation
	DOUBLE FINES will be imposed for violating any regulatory speed limits in work zones and School zones.
	Temporary construction zone speed limits are regulatory speed limits established for long term construction projects or detour routes. These black and white signs are used when a reduced speed is needed for driver safety. Valid 24 hours a day, 7 days a week, these must be authorized by the commissioner of transportation for any roadway. click for MnMUTCD specifications on size and sign installation

Questions & Answers

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WILL LOWERING THE SPEED LIMIT REDUCE SPEEDS?

NO. Studies show that there is little change in the speed pattern after the posting of a speed limit. The driver is much more influenced by the roadway conditions.click for multi-year speed trend information (pdf format file)

WILL LOWERING THE SPEED LIMIT REDUCE CRASH FREQUENCY?

NO. Although lowering the speed limit is often seen as a cure-all in preventing crashes, this is not the case. Crashes are most often the result of driver inattention and driver error. However, if a posted speed limit is unrealistically low, it creates a greater speed variance (i.e. some drivers follow the speed limit while most drive the reasonable speed). This speed variance can contribute to crashes. click for crash trend information

WHY DO WE EVEN HAVE SPEED LIMITS?

A uniform speed of vehicles in a traffic flow results in the safest operation. The posted speed limits can keep the traffic flowing smoothly provided the majority of drivers find the speed limits reasonable. To best do this, the limits must be consistent throughout the state.

The speed limits also give the motorist an idea of a reasonable speed to drive in an unfamiliar location.

The speed limits are used by police officials to identify excessive speeds and curb unreasonable behavior.

Who Do I Contact?

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If you believe that there is a safety concern or an inappropriate speed limit posted, the person to contact depends on the type of road.

TRUNK HIGHWAYS

For regulatory and advisory speed limits on the trunk highway system, you may contact the district traffic engineer at your Mn/DOT district office.  click for Mn/DOT District Map

The trunk highway system includes:

• Interstate Highways
• U.S. Highways
• Minnesota State Highways

LOCAL STREETS AND HIGHWAYS

For these roadways, you may contact your local road authority (county, city, or township).

For advisory speed limits

The local road authority can determine these advisory speeds and post the plates without authorization from the commissioner of transportation.

For regulatory speed limits

The local road authority can pass a resolution requesting an investigation by Mn/DOT. Based upon the results, Mn/DOT may then authorize the local road authority to post new speed limits.

The phone numbers to call for state or local assistance can be found in the phone book under government listings. If you are unable to find the proper phone number, you may call the Mn/DOT Information Center at the following numbers:

• 1-800-657-3774 Greater Minnesota or
• 651-296-3000 Twin Cities Metro Area
• Website: www.dot.state.mn.us

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The information contained on this page can be obtained in printed form
in a Mn/DOT brochure titled "SPEED LIMIT ? Here's Your Answer"
Click here for information about receiving the brochure

For more information, please visit the Traffic Engineering Speed Limit Resources Site