Tex. Transportation Code § 366.072

(a) An authority may maintain a feasibility study fund. The fund is a revolving fund held in trust by a banking institution chosen by the authority and shall be kept separate from the money for any turnpike project or system.

(b) An authority may transfer an amount from a surplus fund established for a turnpike project or system to the authority's feasibility study fund if the remainder of the surplus fund is not less than any minimum amount required by the bond proceedings to be retained for that turnpike project or system.

(c) Money in the feasibility study fund may be used only to pay the expenses of studying the cost and feasibility and any other expenses relating to:

(1) the preparation and issuance of bonds for the acquisition and construction of a proposed turnpike project or system;

(2) the financing of the improvement, extension, or expansion of an existing turnpike project or system; and

(3) private participation, as authorized by law, in the financing of a proposed turnpike project or system, the refinancing of an existing turnpike project or system, or the improvement, extension, or expansion of a turnpike project or system.

(d) Money spent under Subsection (c) for a proposed turnpike project or system must be reimbursed from the proceeds of turnpike revenue bonds issued for, or other proceeds that may be used for, the acquisition, construction, improvement, extension, expansion, or operation of the turnpike project or system.

(e) For a purpose described by Subsection (c), an authority may borrow money and issue promissory notes or other interest-bearing evidences of indebtedness payable out of its feasibility study fund, pledging money in the fund or to be placed in the fund.