Md. Code, Local Government § 12-538

(a) The County Commissioners of St. Mary’s County may regulate for any public road, sidewalk, curb, gutter, or storm drainage facility in the county that is not in a municipality and that has not been designated or maintained as a part of the State or federal highway system relating to:

(1) vehicle weight;

(2) vehicle parking;

(3) vehicle abandonment;

(4) building or maintenance by a private or public utility necessary for the performance of the utility’s purpose;

(5) building or maintenance of driveway connections where connections are provided; and

(6) vehicle speed.

(b) (1) This subsection applies to roads proposed for subdivisions, including sidewalks, curbs and gutters, driveway entrances, and storm drainage facilities and appurtenances to be located in the subdivision.

(2) The County Commissioners of St. Mary’s County shall enact, by ordinance, rules and regulations that govern the grading, building, improving, maintaining, and repairing of roads, used or intended for use by the public.

(c) If required by an ordinance enacted under subsection (a) of this section, the County Commissioners of St. Mary’s County shall provide appropriate traffic control devices.

(d) For a new road, sidewalk, curb, gutter, or storm drainage facility, the County Commissioners of St. Mary’s County may regulate relating to:

(1) engineering;

(2) construction; and

(3) acceptance of the road, sidewalk, curb, gutter, or storm drainage facility into the county roads system.