55 ILCS 5/5-34004
The Expressway bonds shall be of such form and denomination, payable at such place, bear such date, and be executed by such officials as may be provided by the Board of Commissioners in the bond resolution or resolutions. They shall mature within not to exceed 20 years from their date, and may be made callable on any interest payment date at par and accrued interest after notice has been given at the time and in the manner provided in the bond resolution or resolutions. If there is no default in payment of principal or of interest on the Expressway bonds, and after setting aside a sum of money equal to the amount of interest that will accrue on the Expressway bonds, and a sum of money equal to the amount of principal that will become due thereon within the next six months period, the Treasurer and Comptroller, if there is a Comptroller, of the county shall use the moneys available from the proceeds of the taxes levied for the payment of Expressway bonds and the moneys available from the State of Illinois applicable to such bonds in calling them for payment, if, by their terms, they are subject to redemption. Expressway bonds called for payment and paid shall be marked paid and cancelled.
55 ILCS 5/5-34004