Whenever any roadway has been divided into two or more clearly marked lanes for traffic, the following shall apply:
(A) Lane driving required. On a roadway divided into lanes, a vehicle shall be driven as nearly as practicable entirely within a single lane and may not be moved from such lane until the driver has first ascertained that such movement can be made with safety.
(SDCL § 32-26-6)
(B) Three-lane highway. Upon a roadway which is divided into three lanes, a vehicle may 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 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 marked or signposted to give notice of such allocation.
(SDCL § 32-26-7)
(C) Slow moving traffic lane. Official signs may be erected on a roadway divided into lanes 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 and drivers of vehicles shall obey the directions of every such sign.
(SDCL § 32-26-8)
(D) Highway divided by physical barrier. If any highway has been divided into two roadways by leaving an intervening space or by a physical barrier or clearly indicated dividing section so constructed as to impede vehicular traffic, every vehicle shall be driven only upon the right-hand roadway and no vehicle may be driven over, across, or within any such dividing space, barrier, or section, except through an opening in such physical barrier or dividing section or at a crossover or intersection established by public authority.
(SDCL § 32-26-9) Penalty, see § 70.99