From the Maryland Drivers Manual:
All traffic laws apply to drivers of mopeds and motor scooters. Drivers of cars must always be alert for mopeds and scooters, as their size makes them very difficult to see.
Mopeds and scooters may be ridden on any roadways where the posted maximum speed limit is 50 miles per hour or less. They may be riding side-by-side or alone, and on the roadway or on the shoulder. Generally, they are to be ridden as near to the right side of the roadway as practical and safe.