Whenever lane-control signals are used in conjunction with official signs, they shall have the following meanings:
(A) Downward-pointing green arrow. A driver facing this indication is permitted to drive in the lane over which the arrow signal is located. Otherwise, he shall obey all other traffic-controls present and follow normal safe driving practices.
(B) Red X symbol. A driver facing this indication shall not drive in the lane over which the signal is located, and this indication shall modify accordingly the meaning of all other traffic-controls present. Otherwise he shall obey all other traffic controls, and follow normal safe driving practices.
(C) Yellow X (steady). A driver facing this indication should prepare to vacate the lane over which the signal is located, in a safe manner to avoid, if possible, occupying that lane when a steady red X is displayed.
(D) Flashing yellow arrow. A driver facing this indication may use the lane only for the purpose of approaching and making a left turn.
(ILCS Ch. 625, Act 5, § 11-308) Penalty, see § 70.999