A common belief is that posting a speed limit sign will influence drivers to drive at that speed, but facts indicate otherwise. Research has shown that drivers are influenced more by the appearance of the road itself and the prevailing traffic conditions than by the posted speed limit. Basic speed laws require that "No person shall drive a vehicle on a highway at a speed greater than is reasonable and prudent under the conditions."
The maximum speed limit for any passenger vehicle in Minnesota is as follows:
Rural interstate highways: 70 miles per hour
Urban interstate highways: 55 or 65 miles per hour
Expressways: 55 miles per hour
Other roads: 55 miles per hour
Residential streets: 30 miles per hour
The speed limits are not always posted but all motorists are required to know these basic speed laws.
Intermediate speed limits between 30 and 55 miles per hour may be established by the Minnesota Department of Transportation based on traffic engineering surveys. These surveys include an analysis of roadway conditions, accident records, and the prevailing speed of prudent drivers. If speed limit signs are posted for a lower limit than is needed to safely meet these conditions, many drivers will simply ignore the signs. This generally increases the conflicts between faster and slower drivers by reducing the gaps in traffic through which crossings could be made safely and increases the difficulty for pedestrians to judge the speed of approaching vehicles. Studies have shown that when uniformity of speed is not maintained, accidents generally increase. Speed limits are determined by State Statute with speed studies performed by the State.