55 ILCS 5/5-34006
Moneys received from the proceeds of taxes levied for the payment of principal of and interest on Expressway bonds and moneys received from the State of Illinois applicable to such payment of principal of and interest on Expressway bonds shall be deposited in a special account hereby required to be created and which shall be designated as the "Expressway Bond and Interest Sinking Fund Account of the County of ....". If more than one resolution authorizing Expressway bonds is adopted, a separate sinking fund account shall be created for the Expressway bonds issued pursuant to each such resolution. The moneys in each such sinking fund account shall be faithfully applied to the payment of Expressway bonds and interest thereon as provided in this Division. If the moneys in such sinking fund account or accounts is not immediately necessary for the payment of Expressway bonds and interest thereon, then, under the direction of the Board of Commissioners of the County, the moneys may be invested by the Treasurer and the Comptroller, if there is a Comptroller of the County, in the bonds or other interest-bearing obligations of the United States or in bonds of the State of Illinois. The maturity date of the securities in which these moneys are invested shall be prior to the due date of the particular issue of Expressway bonds of the investing county. The Board of Commissioners may cause these securities to be sold whenever necessary to obtain cash to meet bond and interest payments.
55 ILCS 5/5-34006