605 ILCS 5/5-701.1
Any county board may use any motor fuel tax money allotted to it for the construction of (1) highways within the county designated as county highways, or (2) county highways within the corporate limits of any municipality within such county, or (3) county highways within the corporate limits of any park district within such county, or (4) any county highway to be constructed under Section 5-406 of this Code. Such construction shall be in accordance with the procedure prescribed in Section 5--403 of this Code.
So far as practicable, priority in the matter of construction with motor fuel tax funds in any county shall be given county highways which will join municipalities and communities not upon any State highway, or not upon federal aid highways which may now or may hereafter be designated, with such highways; and county highways shall be selected for construction according to their relative importance from the standpoint of traffic needs and county-wide service and so as to make available as rapidly as practicable continuous or connected improved traffic routes, such selection to be made by the county board with the approval of the Department.
605 ILCS 5/5-701.1