70 ILCS 1505/25.4

Whenever bonds are issued as provided by sections 25.1 to 25.9, both inclusive, of this Act as now enacted and as may hereafter be amended, it shall be the duty of the Commissioners to establish charges and fees for the use of any such parking facilities sufficient at all times to pay maintenance and operation costs, and principal of and interest upon such bonds, and all revenues derived from the operation thereof shall be set aside as a separate fund and account and used only as hereinafter provided.