625 ILCS 5/12-205
Every vehicle, including animal drawn vehicles, referred to in paragraph (b) of Section 12-101, not specifically required by the provisions of this Article to be equipped with lamps or other lighting devices, shall at all times specified in Section 12-201 of this Act be equipped with at least 2 lamps on the power or towing unit, displaying a white light visible from a distance of not less than 1,000 feet to the front of such vehicle and shall also be equipped with 2 lamps each displaying a red light visible from a distance of not less than 1,000 feet to the rear of such vehicle.
Where the towed unit or any load thereon partially or totally obscures the 2 lamps displaying red light to the rear of the towing unit, the rearmost towed unit shall be equipped with 2 lamps displaying red light visible from a distance of not less than 1,000 feet to the rear of such towed unit which are positioned in such a manner as to not obstruct the visibility of the red light to any vehicle operator approaching from the rear of such vehicle or combination of vehicles.
Where the 2 lamps displaying red light are not obscured by the towed unit or its load, then either towing unit or towed unit, or both, may be equipped with the 2 lamps displaying red light as required.
The preceding paragraph does not apply to antique vehicles, expanded-use antique vehicles, custom vehicles, or street rods. An antique vehicle or expanded-use antique vehicle shall be equipped with lamps of the same type originally installed by the manufacturer as original equipment and in working order.
625 ILCS 5/12-205