605 ILCS 5/6-701.1
The highway commissioners of the several road districts, in cooperation with the county superintendent of highways of their respective counties, shall select the roads and grade separations to be constructed with motor fuel tax funds. In the selection of roads, preference shall be given to public school bus routes and rural free delivery mail routes. The county superintendent of highways, in cooperation with the respective highway commissioners, shall prepare, or cause to be prepared maps showing the roads and grade separations selected and shall prepare the necessary plans, specifications and estimates of cost of such construction, all of which shall be submitted to the Department for approval. The type of construction selected shall be adequate for present or reasonably anticipated traffic needs as determined by the county superintendent of highways and the respective highway commissioners and approved by the Department.
The construction provided for in this Section may be done by contract or day labor with county or road district equipment and forces as the county superintendent of highways and the respective highway commissioners may determine. Contracts shall be advertised for and let by the county board to the lowest responsible bidder subject to the approval of the highway commissioner and such contracts also shall be subject to approval by the Department. The construction work shall be carried on under the immediate supervision of the highway commissioner and under the general supervision of the county superintendent of highways and all work upon such projects shall be subject to approval by the Department.
In any county in which a county unit road district has been created the county superintendent of highways for such county shall perform all of the functions of a highway commissioner under this Section with respect to the district roads in such county.
605 ILCS 5/6-701.1