Continuation of tolls upon provision for payment of bondholders and assumption of maintenance by department.

When all revenue bonds issued under the provisions of ss. 338.22-338.241 in connection with the turnpike system and the interest on the bonds have been paid, or an amount sufficient to provide for the payment of all such bonds and the interest on the bonds to the maturity of the bonds, or such earlier date on which the bonds may be called, has been set aside in trust for the benefit of the bondholders, the department may assume the maintenance of the turnpike system as part of the State Highway System, except that the turnpike system shall remain subject to sufficient tolls to pay the cost of the maintenance, repair, improvement, and operation of the system and the construction of turnpike projects.