20 ILCS 2705/2705-505

The Department shall, where economically feasible and safe, install along various interstate highways and other freeways with full control of access, except those that are toll highways, signs to alert motorists of the travel-related facilities available in communities served by upcoming interstate exits. The Department may also install, along other rural State highways, signs to alert motorists of the tourist-oriented businesses available on intersecting highways and roads under local jurisdiction in rural areas. The Department has the authority to sell or lease space on the signs to the owners or operators of the facilities and to promulgate rules and regulations for the leasing or purchasing of space.