Many states based their minimum speed limits on the Uniform Vehicle Code (UVC) published by the National Committee of Uniform Traffic Laws and Ordinances (National Committee 1954).
By 1962 40 MPH was the 'standard' minimum speed limit on Interstates in majority of states......Michigan and North Carolina maintained a 45 mph minimum speed rule on their interstate highways.
But after the National Highway System Designation Act of 1995 repealed the federally sanctioned maximum speed limit......the minimum speed limit was called into question.
By 2003 only 14 states still use 40 mph minimum speed limit signs, 10 states use 45 mph, and 1 state uses 55 mph. 25 states do not post minimum speed limit signs........"impeding traffic flow," can be used to warn or cite slow drivers.
SO....what does this mean????
Don't drive slower then posted minimum IF posted. Otherwise don't impede the flow of traffic
US DOT.......Speed on Rural Interstates/Relative to Posting 40MPH Min When (IF) I am on an Interstate (rarely) I don't care what Max Speed Limit is I'm staying at 62-65MPH when towing.