Md. Code, Transportation § 21–1203

(a) The operator of a bicycle or a motor scooter may ride the bicycle or motor scooter only:

(1) On or astride a permanent and regular seat securely attached to it; or

(2) For an electric low speed scooter, by standing on a platform designed to carry the operator.

(b) A bicycle may not carry any passenger unless it is designed for and equipped with a seat securely attached to it for each passenger.

(c) A motor scooter may not carry any passenger unless it is designed for and equipped with a seat securely attached to it and footrests for each passenger.