Maryland Code, Transportation § 21-803

(a)(1) Except as provided in paragraphs (3) through (5) of this subsection, if, on the basis of an engineering and traffic investigation, a local authority determines that any maximum speed limit specified in this subtitle is greater or less than reasonable or safe under existing conditions on any part of a highway in its jurisdiction, it may establish a reasonable and safe maximum speed limit for that part of the highway, which may:

(2) An engineering and traffic investigation is not required to conform a posted maximum speed limit in effect on December 31, 1974, to a different limit specified in § 21-801.1(b) of this subtitle.

(3) Calvert County may decrease the maximum speed limit to not less than 15 miles per hour on Lore Road and, except for Solomons Island Road, each highway south of Lore Road without performing an engineering and traffic investigation, regardless of whether the highway is inside an urban district.

(5) Baltimore City may, without performing an engineering and traffic investigation:

(1) The county may decrease the maximum speed limit to 15 miles per hour during school hours, provided the county pays the cost of placing and maintaining the necessary signs; and

(2) Any municipality within each county may decrease the maximum speed limit in a school zone within the municipality to 15 miles per hour during school hours, provided the municipality pays the cost of placing and maintaining the necessary signs.

(e)(1) If a local authority determines that any maximum speed limit specified in this subtitle is greater than reasonable or safe in an alley in its jurisdiction, the local authority may establish a reasonable and safe maximum speed limit for the alley.

(2) The local authority shall post a speed limit established under this subsection on appropriate signs giving notice of the speed limit.