605 ILCS 5/6-508
Such tax, when collected, shall constitute and be held by the treasurer of the district as a separate fund to be expended for the construction or repair of bridges, culverts, drainage structures or grade separations, including approaches thereto, at the joint expense of the county and the road district. The highway commissioner shall separately specify in the certificate required by Section 6-501 the amount necessary to be raised by taxation for the purpose of constructing or repairing bridges, culverts, drainage structures or grade separations, including approaches thereto, at the joint expense of the county and the road district. Upon the approval by the county board of the amount so certified as provided in Section 6-501 of this Code, the county clerk shall extend the same against the taxable property of the road district, provided the amount thus approved shall not be extended at a rate in excess of .05% of value, as equalized or assessed by the Department of Revenue.
When any improvement project for which a tax may be levied under this Section has been ordered as provided in Section 5-501 and the estimated cost of such project to the road district is in excess of the amount that will be realized from the annual tax levy authorized by this Section when extended and collected, then the road district may accumulate the proceeds of such tax for such number of years as may be necessary to acquire the funds necessary to pay the district's share of the cost of such project. In counties in which a property tax extension limitation is imposed under the Property Tax Extension Limitation Law and the imposition of the property tax extension limitation prevents a road district from levying taxes for road purposes at the required rate, a road district may retain its eligibility if, at the time the property tax extension limitation was imposed, the road district was levying at the required rate and continues to levy the maximum allowable amount after the imposition of the property tax extension limitation. It shall not be a valid objection to any subsequent tax levy made under this Section that there remains unexpended money arising from a preceding levy of a prior year because of the accumulation provided for in this Section.
The rate limitation imposed by this Section may be increased for a 10 year period to up to 0.25% of the value of all the taxable property in the road district, as equalized or assessed by the Department of Revenue if the proposition for the increased tax rate is submitted under Sections 6-504 and 6-505 and receives a majority of all ballots cast on the proposition at the election held under Section 6-505.
605 ILCS 5/6-508