Maryland Transportation Section 21-201
(a)   (1)   Subject to the exceptions granted in this title to the driver of an emergency vehicle, the driver of any vehicle, unless otherwise directed by a police officer, shall obey the instructions of any traffic control device applicable to the vehicle and placed in accordance with the Maryland Vehicle Law.
(2)   The driver of a vehicle approaching an intersection controlled by a traffic control device may not drive across private property or leave the roadway for the purpose of avoiding the instructions of a traffic control device.
(b)   (1)   If a provision of the Maryland Vehicle Law or of an ordinance or regulation of a local authority requires a traffic control device, the provision is unenforceable against an alleged violator if, at the time and place of the alleged violation, the traffic control device is not in proper position and legible enough to be seen by an ordinarily observant individual.
(2)   Unless a provision of the Maryland Vehicle Law or of an ordinance or regulation of a local authority states that a traffic control device is required, the provision is effective and enforceable even if no traffic control device is in place.
(c)   Unless the contrary is established by competent evidence, if a traffic control device is placed in a position approximately meeting the requirements of the Maryland Vehicle Law, the device is presumed to have been placed by the official act or direction of lawful authority.
(d)   Unless the contrary is established by competent evidence, if a traffic control device is placed in accordance with the Maryland Vehicle Law and purports to meet the lawful requirements governing these devices, the device is presumed to meet the requirements of the Maryland Vehicle Law.