40-6-40.
   
  (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 such movement;
   
    (2) When an obstruction exists making it necessary to drive to the
    left of the center of the highway, provided that any person so
    doing shall yield the right of way to all vehicles traveling in
    the proper direction upon the unobstructed portion of the highway
    within such a distance as to constitute an immediate hazard;
   
    (3) Upon a roadway divided into three marked lanes for traffic
    under the rules applicable thereon; or
   
    (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 of the roadway except when
  authorized by official traffic-control devices designating certain
  lanes to the left of the center of the roadway for use by traffic
  not otherwise permitted to use such lanes or except as permitted
  under paragraph (2) of subsection (a) of this Code section. However,
  this subsection shall not be construed as prohibiting the crossing
  of the center of the roadway in making a left turn into or from an
  alley, private road, or driveway.
   
  (d) No two vehicles shall impede the normal flow of traffic by
  traveling side by side at the same time while in adjacent lanes,
  provided that this Code section shall not be construed to prevent
  vehicles traveling side by side in adjacent lanes because of
  congested traffic conditions.