(a) The principal of, interest on, and any redemption premium on bonds issued by the commission under this subchapter are payable solely from:
(1) the revenue of the toll project or system for which the bonds are issued, including tolls pledged to pay the bonds;
(2) the proceeds of bonds issued for the project or system;
(3) the amounts deposited in a debt service reserve fund as required by the trust agreement securing bonds issued for the project or system;
(4) amounts received under a credit agreement relating to the project or system for which the bonds are issued;
(5) surplus revenue of another project or system as authorized by Section 228.006; and
(6) amounts received by the department:
(A) as pass-through tolls under Section 222.104;
(B) under an agreement with a local governmental entity entered into under Section 228.254;
(C) under other agreements with a local governmental entity relating to the project or system for which the bonds are issued; and
(D) under a comprehensive development agreement entered into under Section 223.201.
(b) Bonds issued under this subchapter do not constitute a debt of the state or a pledge of the faith and credit of the state. Each bond must contain on its face a statement to the effect that:
(1) the state, the commission, and the department are not obligated to pay the bond or the interest on the bond from a source other than the amount pledged to pay the bond and the interest on the bond; and
(2) the faith and credit and the taxing power of the state are not pledged to the payment of the principal of or interest on the bond.

(c) The commission and the department may not incur financial obligations that cannot be paid from tolls or revenue derived from owning or operating toll projects or systems or from money provided by law.