§ 20-85  DRIVING ON RIGHT SIDE OF ROADWAYS; EXCEPTIONS.
   (A)   Upon all roadways or 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 the movement;
      (2)   When the right-half of a roadway is closed to traffic while under construction or repair;
      (3)   Upon a roadway divided into three marked lanes for traffic under the rules applicable thereon;
      (4)   Upon a roadway designated and signposted for one-way traffic;
      (5)   When an obstruction exists making it necessary to drive to the left of the center of the highway; 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 highway within such distance as to constitute an immediate hazard; and
      (6)   Upon a roadway having four or more lanes for moving traffic and providing for two-way movement of 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.
(47 O.S. § 11-301)  (`90 Code, § 20-34)
Statutory reference:
   Driving on right side of road, 47 O.S. §§ 11-301 et seq.