When all bonds issued under the provisions of this article and the interest thereon shall have been paid or a sufficient amount for the payment of all such bonds and the interest thereon to the maturity thereof shall have been set aside in trust for the benefit of the bondholders, such projects, if then in good condition and repair to the satisfaction of the Commission, shall become part of the state highway system and shall thereafter be maintained by the Commission free of tolls. Provided, that when all bonds for any turnpike project and the interest thereon shall have been paid or such provision for payment made, prior to payment of the bonds and interest on any other project or projects, such project shall continue to be operated as a toll facility at toll rates not less than the lowest rate being charged on any project, until all bonds issued by the Authority and the interest thereon shall have been paid or such provisions for payment made. The revenues of such paid-out projects shall be used and applied by the Authority in paying the obligations or depositing in the sinking fund of such other turnpike projects in the following order:
Okla. Stat. tit. 69, § 1717