(a) An authority may pay the expenses of studying the cost and feasibility of a transportation project, the design and engineering of a transportation project, and any other expenses relating to the preparation and issuance of bonds for a proposed transportation project by:
(1) using legally available revenue derived from an existing transportation project;
(2) borrowing money and issuing bonds or entering into a loan agreement payable out of legally available revenue anticipated to be derived from the operation of an existing transportation project;
(3) pledging to the payment of the bonds or a loan agreement legally available revenue anticipated to be derived from the operation of transportation projects or revenue legally available to the authority from another source; or
(4) pledging to the payment of the bonds or a loan agreement the proceeds from the sale of other bonds.
(b) Money spent under this section for a proposed transportation project must be reimbursed to the transportation project from which the money was spent from the proceeds of bonds issued for the acquisition and construction of the proposed transportation project, unless the transportation projects are or become part of a system under Section 370.034.
(c) The use of any money of a transportation project to study the feasibility of another transportation project or used to repay any money used for that purpose does not constitute an operating expense of the transportation project producing the revenue and may be paid only from the surplus money of the transportation project as determined by the authority.