(a) The commission shall authorize the use of surplus revenue of a toll project or system to pay the costs of a transportation project, highway project, or air quality project within a region in which any part of the toll project is located.
(a-1) The department shall allocate the distribution of the surplus toll revenue to department districts in the region that are located in the boundaries of the metropolitan planning organization in which the toll project or system producing the surplus revenue is located based on the percentage of toll revenue from users in each department district of the project or system. To assist the department in determining the allocation, each entity responsible for collecting tolls for a project or system shall calculate on an annual basis the percentage of toll revenue from users of the project or system in each department district based on the number of recorded electronic toll collections.
(b) The commission may not revise the formula as provided in the department’s unified transportation program, or its successor document, in a manner that results in a decrease of a district’s allocation because of a payment under Subsection (a).
(c) The commission may not take an action under this section that violates, impairs, or is inconsistent with a bond order, trust agreement, or indenture governing the use of the surplus revenue.