Maryland Code, Transportation § 21-304

(1) If the overtaken vehicle is making or about to make a left turn;

(2) On a highway with unobstructed pavement not occupied by parked vehicles and wide enough for two or more lines of vehicles moving lawfully in the same direction as the overtaking vehicle; or

(3) On any one-way roadway, if the roadway is free from obstruction and wide enough for two or more lines of moving vehicles.

(c)(1) Except as provided in paragraph (2) of this subsection and for an operator of a bicycle or motor scooter, a person may not make the movement described under subsections (a) and (b) of this section by driving off the roadway.

(2) The driver of a vehicle may make the movement described under subsections (a) and (b) of this section by driving outside the marked lane onto the shoulder to overtake and pass a vehicle that is making or about to make a left turn if the driver can do so without leaving the paved surface.