Md. Code, Transportation § 21–308

(a) (1) The State Highway Administration may designate any highway or any separate roadway under its jurisdiction for one-way traffic and shall place appropriate signs giving notice of the designation.

(2) On a roadway designated and signposted for one-way traffic, a vehicle may be driven only in the direction designated.

(b) A vehicle passing around a rotary traffic island may be driven only to the right of the island.