(A) Whenever any roadway has been divided into two or more clearly marked lanes for traffic, in addition to all other rules consistent with this division (A), a vehicle shall be driven as nearly as practical entirely within a single lane and shall not be moved from the lane until the driver has first ascertained that the movement can be made with safety and then given a signal not less than 100 feet traveled by the vehicle of the driver's intention to change lanes.
(B) Where streets or roadways do not have marked traffic lanes, vehicles shall nevertheless keep in line or follow a straight course as nearly as practical and shall not weave in and out or turn from side to side unnecessarily. Vehicles shall move to the right or left only as necessary in slowing or stopping adjacent to the curb, in passing slow moving vehicles or making a proper approach for a turn, and this only after the driver has first ascertained that such movement can be made safely and has signalled for a change of course.
(C) Upon a roadway which has been divided into three lanes, a vehicle shall not be driven in the center lane except when overtaking and passing another vehicle where the roadway is clearly visible and such center lane is clear of traffic within a safe distance, or in preparation for a left turn, or where such center lane is at the time allocated exclusively to traffic moving in the direction the vehicle is proceeding and is signposted to give notice of such allocation.
(D) Official signs may be erected directing slow-moving traffic to use a designated lane or designating those lanes to be used by traffic moving in a particular direction regardless of the center of the roadway. Drivers of vehicles shall obey the directions of every such sign.
(E) Upon a roadway which is divided into four or more lanes, a vehicle proceeding at less than the maximum posted speed, except when reduced speed is necessary for safe operation, shall not impede the normal flow of traffic by driving in the left lane. Such vehicle shall be driven in the right-hand lane except when overtaking and passing another vehicle proceeding in the same direction or when preparing for a turn at an intersection or into a private road or driveway.
(47 O.S. § 11-309) (`83 Code, § 15-501) (Ord. 98-49, passed 12-21-98) Penalty, see § 71.999