(a) The toll bridge revenue fund is established as a separate fund of the state. The revenue fund consists of all revenue, fees, charges, and rentals received by the state, by contract with the authority or otherwise, from the ownership or operation of toll bridges and facilities and improvements used in connection with the toll bridges and facilities. Contracts or other agreements with the authority may establish priorities for the payment of operation and maintenance costs of the authority. The money in the revenue fund may be used only

1. (1) to pay or secure payment of the principal of and interest on bonds;
2. (2) to redeem bonds before their fixed maturities;
3. (3) to pay indebtedness to the Federal Highway Administration, United States Department of Transportation; and
4. (4) subject to appropriation by the legislature, for any other purpose for which federal funds may be obligated by the state under 23 U.S.C. 129(a).