A common belief is that posting a speed limit sign will influence drivers to drive at that speed. 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 at a speed greater than reasonable in regard to weather, visibility, traffic and the surface and width of the roadway. Under no circumstances, at a speed that endangers the safety of persons or property."
The maximum speed limit for any passenger vehicle in Minnesota is as follows:
- Freeways outside urban districts - 65 or 70 miles per hour
- Urban freeway and highways - 55 or 60 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 safety 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.