The department is authorized to refund, at the maturity thereof, or before the maturity thereof if they are subject to call prior to maturity or if all of the holders thereof consent thereto, upon such terms and conditions as it deems best, any or all of its revenue bonds now or hereafter outstanding, issued for the purpose of acquiring, constructing, or reconstructing any toll bridge, toll road, toll tunnel, ferry system, or any other toll facility of any sort, or issued for the purpose of refunding such bonds, which revenue bonds are payable out of all or part of the revenues of the toll facility. Refunding bonds may be issued hereunder in a sufficient amount to provide additional funds for acquiring, constructing, reconstructing, rehabilitating, rebuilding, enlarging, or improving any toll bridge, toll road, toll tunnel, ferry system, or any other toll facility of any sort, and to pay all refunding costs and expenses and to provide adequate reserves for the toll facility and for any such refunding bonds. Various issues and series of such outstanding bonds, including refunding bonds, may be combined and refunded by a single issue of refunding bonds. The refunding bonds shall bear interest at such rates and mature at such times, without limitation by the interest rates or maturity of the bonds being refunded, and shall contain such other covenants and conditions as the department determines by resolution.