Ill. Admin. Code tit. 92, § 544.30 – Traffic Signals

a) Signals may be installed only where conditions meet the warrants established in the current State of Illinois Manual on Uniform Traffic Control Devices for Streets and Highways to be codified as 92 Ill. Adm. Code 546 or supplemental Department policy.
b) The Department may regulate signal sequences and control timing of all signals on State highways when it deems it necessary to do so.