(a) Upon all roadways of sufficient width, a vehicle shall be driven upon the right half of the roadway, except under any of the following conditions:
(1) When overtaking and passing another vehicle proceeding in the same direction under the rules governing such movement.
(2) When an obstruction exists making it necessary to drive to the left of the center of the highway; provided, any person doing so shall yield the right-of-way to all vehicles traveling in the proper direction upon the unobstructed portion of the highway 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.
(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 then 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 such lanes, or except as permitted under subdivision (a)(2). However, this subsection 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.
(d)(1) Upon any interstate highway, except as provided in subdivision (2), a vehicle may not remain in the leftmost lane for more than 1.5 miles without completely passing another vehicle.
(2) A vehicle may travel in the leftmost lane under any of the following conditions:
a. When traffic conditions or congestion make it necessary to operate a vehicle in the leftmost lane.
b. When inclement weather, obstructions, or hazards make it necessary to operate a vehicle in the leftmost lane.
c. When compliance with a law, rule, ordinance, or traffic control device makes it necessary to operate a vehicle in the leftmost lane.
d. When exiting a roadway to the left.
e. When paying a toll or user fee at a toll collection facility.
f. If the vehicle is an authorized emergency vehicle operated in the course of duty.
g. If the vehicle is operated or used in the course of highway maintenance or construction or is traveling through a construction zone.
(3) Until October 31, 2019, a law enforcement officer may issue only a warning citation for a violation of this subsection.