605 ILCS 5/9-102
The proper highway authorities are authorized to keep vehicles of every kind off the public highways where necessary to properly construct or repair the same.
Whenever any public highway including any bridge or culvert thereon is being constructed or repaired, the highway authorities having such work in charge shall, when they deem it necessary, erect or cause to be erected at such points as they deem desirable, suitable barriers, with signs thereon, stating that such highway is closed.
Such authorities shall also erect or cause to be erected at such places as they deem best, detour signs directing travel around such construction or repair work.
Such signs and barricades shall conform to the Manual of Uniform Traffic Control Devices adopted by the Department.
605 ILCS 5/9-102