Md. Code, Transportation § 3–512

(a) The bonds shall be payable solely from the revenues received by the Department from the participating counties for that purpose.

(b) The revenues of the State and the Department are not pledged, and may not be used, to pay the principal of or interest on the bonds.

(c) The Transportation Trust Fund established by § 3-216 of this title is not pledged, and may not be used, to pay the principal of or interest on the bonds.