Tex. Transp. Code § 366.175

The board of an authority may by resolution authorize the use of surplus revenue of a turnpike project or system to pay the costs of another turnpike project or system other than a project financed under Subchapter G. The board may in the resolution prescribe terms for the use of the revenue, including the pledge of the revenue, but may not take an action under this section that violates, impairs, or is inconsistent with a bond resolution, trust agreement, or indenture governing the use of the surplus revenue.