Maryland Code, Transportation § 21-313

(a) The State Highway Administration, by order, or any local authority, by ordinance, may prohibit the use of any controlled access highway in its jurisdiction by parades, low speed vehicles, funeral processions, bicycles, or other nonmotorized traffic or by any person operating a motorcycle.

(b) The County Commissioners of Charles County and Washington County and the governing body of Frederick County, by ordinance, may prohibit the use of any controlled access highway in the county's jurisdiction by any person to solicit money, donations of any kind, employment, business, or a ride from the occupant of any vehicle on the controlled access highway.

(c) The State Highway Administration or the local authority adopting any prohibition under this section shall place and maintain signs on the controlled access highway to which the prohibition is applicable. If signs are so placed, a person may not disobey the restrictions stated on them.