Md. Code, Transportation § 13–629

Any person to whom special registration plates have been issued under the law relating to common carriers, as set forth in § 13-423(a) of this title, may, after notifying the Administration of his intention to do so:

(1) Transfer, for a period of not more than 15 days, the registration plates to a motor vehicle owned by a manufacturer; and

(2) Operate the vehicle over the existing route or routes for a trial or demonstration period.