605 ILCS 5/4-201.12
Except as provided in the Illinois Adopt-A-Highway Act, to place, erect and maintain on highways all traffic control devices and signs authorized by this Code or by Chapter 11, Article III of the Illinois Vehicle Code.
To place, erect and maintain on highways signs or surface markings or both to indicate officially designated bicycle routes. Whenever the Department is going to permanently remove route markings from a State highway within a municipality, it shall notify that municipality at least 90 days before such removal.
To acquire right-of-way, plan, locate, relocate, construct, reconstruct, maintain, alter, improve, vacate and regulate the use of officially designated bikeways, as defined in Section 2 of the Bikeway Act.
605 ILCS 5/4-201.12