NO STATE in the US requires Motorhomes to stop period. Read Md commercial law NOTE the CMV!
5. What is the definition of a commercial vehicle?
The Federal Motor Carrier Safety Regulations have defined a commercial motor vehicle (CMV) as noted below. Maryland has adopted this definition for commercial vehicles that operate only within state boundaries (intrastate).
CMV definition:
Commercial motor vehicle means any vehicle operated in interstate commerce to transport passengers or property when the vehicle—
(1) Has a gross vehicle weight rating or gross combination weight rating, or gross vehicle weight or gross combination weight, of 10,001 pounds or more, whichever is greater; or
(2) Is designed or used to transport more than 8 passengers (including the driver) for compensation; or
(3) Is designed or used to transport more than 15 passengers, including the driver, and is not used to transport passengers for compensation; or
(4) Is used in transporting hazardous materials in a quantity requiring placarding.
If it said all vehicle over 10k must stop they'd be lined up to Kalamazoo and in 4 million miles of driving I've never seen a cop run a MH down for passing the scales.