605 ILCS 5/4-501
The Department, in its name, or any county may acquire the fee simple title, or such lesser interest as may be desired, to any land, rights, or other property necessary for the construction, maintenance or operation of State highways, or necessary for locating, relocating, extending, widening or straightening any State highway, or necessary for locating, relocating, extending, widening or straightening an existing street or for laying out, establishing or opening a new street within the corporate limits of any municipality which has been designated by the Department as a street to form a part of or to connect with a State highway leading up to the corporate limits of such municipality, or necessary for any other purpose or use contemplated by this Code by purchase or by the exercise of the right of eminent domain under the eminent domain laws of this State and the Department shall not be required, in any case, to furnish bond.
When, in the judgment of the acquiring agency, it is more practical and economical to acquire the fee to the inaccessible remnants of the tracts of land from which rights-of-way are being acquired than to pay severance damages, such agency may do so by purchase or by an eminent domain proceeding.
When a part of a parcel of land is to be taken for State highway purposes and the accessible remnant is to be left in a shape or condition rendering it of little value to the owner or giving rise to claims for severance or other damages, upon written request of the owner, the acquiring agency may take the whole parcel and may sell or exchange the part not needed for highway purposes.
When acquiring land for a highway on a new location, and when a parcel of land one acre or less in area contains a single family residence, which is in conformance with existing zoning ordinances, and only a part of that parcel is required for State highway purposes causing the remainder of the parcel not to conform with the existing zoning ordinances, or when the location of the right of way line of the proposed highway reduces the distance from an existing single family residence to the right of way line to 10 feet or less, the acquiring agency shall, if the owner so demands, take the whole parcel by negotiation or condemnation. The part not needed for highway purposes may be rented, sold or exchanged by the acquiring agency.
When any farm land is acquired for State highway purposes by the exercise of the right of eminent domain, the rate of compensation to be paid by the acquiring agency shall be computed by taking into consideration the total acreage originally involved in the farm land parcel, including that portion of such parcel already part of a right of way for highway purposes but for which legal title lies in the owner of the parcel.
605 ILCS 5/4-501