(A) Upon all roadways of sufficient width, a vehicle shall be driven upon the right half of the roadway, except as follows:
(1) When overtaking and passing another vehicle proceeding in the same direction under the rules governing those movements;
(2) When an obstruction exists making it necessary to drive to the left of the center of the roadway; provided, any person so doing shall yield the right-of-way to all vehicles traveling in the proper direction upon the unobstructed portion of the roadway within such distance as to constitute an immediate hazard;
(3) Upon a roadway divided into three marked lanes for traffic under the rules applicable thereon;
(4) Upon a roadway restricted to one-way traffic;
(5) Whenever there is a single-track paved road on one side of the public highway and two vehicles meet thereon, the driver on whose right is the wider shoulder shall give the right-of-way on the pavement to the other vehicle.
(B) Upon all roadways, any vehicle proceeding at less than the normal speed of traffic at the time and place and under the conditions then existing shall be driven in the right-hand lane available for traffic, or as close as practicable to the right-hand curb or edge of the roadway, except when overtaking and passing another vehicle proceeding in the same direction, or when preparing for a left turn at an intersection or into a private road or driveway.
(C) Upon any roadway having four or more lanes for moving traffic, and providing for two-way movement of traffic, no vehicle shall be driven to the left of the center line of the roadway, except when authorized by official traffic-control devices designating certain lanes to the left side of the center of the roadway for use by traffic not otherwise permitted to use the lanes, or except as permitted under division (A) (2). However, this division shall not be construed as prohibiting the crossing of the center line in making a left turn into or from an alley, private road, or driveway.
(ILCS Ch. 625, Act 5, § 11-701) Penalty, see § 70.99