Except as hereinafter provided in this section, when all bonds issued under the provisions of Kan. Stat. Ann. §§ 68-2001 to 68-2020, inclusive, and acts amendatory thereof or supplemental thereto, in connection with any turnpike project 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 project, if then in good condition and repair, shall become a part of the state highway system and shall thereafter be maintained by the department of transportation.

The secretary of transportation, when such project becomes a part of the state highway system, shall have the same power as vested in the authority by Kan. Stat. Ann. § 68-2009, to fix, revise, charge and collect tolls for the use of such turnpike project and to contract for the use of any part thereof and to fix the terms, conditions, rents and rates of charges for such use; and such tolls, rents and rates of charges shall be sufficient to provide enough revenue to maintain, repair, operate, regulate and police such turnpike.

The authority may, however, at any time prior thereto covenant to continue tolls for the use of such project and pledge such tolls to the payment of bonds issued under the provisions of Kan. Stat. Ann. §§ 68-2001 to 68-2020, inclusive, and acts amendatory thereof or supplemental thereto, or Kan. Stat. Ann. §§ 68-2030 to 68-2049, inclusive, and acts amendatory thereof or supplemental thereto, or Kan. Stat. Ann. §§ 68-2044 and amendments thereto and statutes supplemental thereto, in connection with another turnpike project or projects, but any such pledge of tolls of a turnpike project to the payment of bonds issued in connection with another project or projects shall not be effectual until the principal of and the interest on the bonds issued in connection with the first and second mentioned project shall have been paid or provision made for their payment.