605 ILCS 5/10-705
The municipality shall fix rates of toll to be charged for transit over and use of such a bridge. These rates shall be so fixed, charged, and adjusted as to provide revenue at all times sufficient, (1) to pay the reasonable cost of maintaining (including insurance), operating, and repairing the bridge; (2) to provide a sinking fund and reserves sufficient to pay the principal of and interest on the bonds, including refunding bonds, if any, out of the revenue from the bridge, as the bonds mature and fall due; (3) to pay the redemption or repurchase price of all bonds redeemed or repurchased before maturity as provided in this Division of this Article; (4) to fulfill the terms and provisions of any agreement with holders of the bonds; and (5) to provide, in addition to the toll purposes specified in clauses (1) to (4), both inclusive, of this sentence, a sinking fund of accumulated tolls and revenue in such amount (determined by a registered professional engineer and approved by the Secretary of Transportation) that the annual interest therefrom will provide adequate income to pay the reasonable cost and extraordinary expenses of maintaining (including insurance), operating, improving and repairing the bridge when and as long as the municipality operates the bridge as a free bridge. The rates provided for by clause (5) of the preceding sentence may be charged for a period not to exceed 18 months after sufficient funds to pay all bonds, including interest thereon, have been accumulated in the sinking fund provided for by clause (2).
An accurate record of the cost of each bridge, the expenditures for maintaining, operating, and repairing the bridge, and of the daily tolls collected, shall be kept and shall be available for the information of all persons interested. The municipality shall classify in a reasonable way all traffic over the bridge, and the tolls shall be fixed and adjusted by it as to be uniform in their application to all traffic falling within any such reasonable class.
The municipality shall operate the bridge as a toll bridge until all bonds payable out of the revenue thereof are paid in full, and thereafter shall operate the bridge as a free bridge.
605 ILCS 5/10-705