(A) No person may turn a vehicle at an intersection unless the vehicle is in proper position upon the highway as required in § 71.020, or turn a vehicle to enter a private road or driveway, or otherwise turn a vehicle from a direct course, or move right or left upon a roadway unless and until the movement can be made with reasonable safety. No person may so turn any vehicle without giving an appropriate signal in the manner hereinafter provided.
(B) A signal of intention to turn right or left, change lanes, otherwise turn a vehicle from a direct course, move right or left upon a highway, or when required must be given continuously during not less than the last 100 feet traveled by the vehicle within a business or residence district, and the signal must be given continuously during not less than the last 200 feet traveled by the vehicle outside a business or residence district.
(C) No person may stop or suddenly decrease the speed of a vehicle without first giving an appropriate signal in the manner provided in this chapter to the driver of any vehicle immediately to the rear when there is opportunity to give a signal.
(D) The electric turn signal device required in ILCS Ch. 625, Act 5, § 12-208 must be used and operated as prescribed in division (B) of this section to indicate an intention to turn, change lanes, turn a vehicle from a direct course, move right or left upon a highway, or start from a parallel parked position. Unless the conditions of division (B) of this section are met, an electric turn signal device required in ILCS Ch. 625, Act 5, § 12-208 shall not be left in the on position and must not be flashed on one side only on a parked or disabled vehicle, or flashed as a courtesy or “do pass” signal to operators of other vehicles approaching from the rear. However, signal devices may be flashed simultaneously on both sides of a motor vehicle to indicate the presence of a vehicular traffic hazard requiring unusual care in approaching, overtaking, and passing.
(ILCS Ch. 625, Act 5, § 11-804) Penalty, see § 71.999