Subject to such contractual obligations as may be entered into by the commission and the holders of bonds issued under this chapter, the department is authorized to change such rates, rents, fees, and charges from time to time as conditions warrant.

All rates, rents, fees, and charges shall comply with the provisions of any applicable indenture. The bond redemption and interest payments shall, to the extent provided in the indenture, constitute a first, direct and exclusive charge and lien on all such rates, rents, fees, charges, and other revenues and interest thereon received from the use and operation of the regional transit terminal, and on any sinking or other funds created therefrom; and all such rates, rents, fees, charges, and other revenues, together with interest thereon, shall constitute a trust fund for the security and payment of such bonds and, except as and to the extent provided in the indenture with respect to the payment therefrom of expenses for other purposes including administration, operation, maintenance, improvements or extensions of the regional transit terminal or other purposes, shall not be used or pledged for any other purpose so long as such bonds, or any of them, are outstanding and unpaid.

The commission may provide in an indenture that the rates, rents, fees, and charges established are minimum rates, rents, fees, and charges and subject to increase or decrease in accordance only with the terms of the indenture.