Whenever any roadway has been divided into two (2) or more clearly marked lanes for traffic the following rules in addition to all others consistent herewith shall apply:
(1) A vehicle shall be driven as nearly as practical entirely within a single lane and shall not be moved from such lane until the driver has first ascertained that such movement can be made with safety.
(2) 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 and drivers of the vehicles shall obey the directions of every such sign.
(Code 1982, § 23-603)
State law reference—Similar provisions, SDCL § 32-26-5 et seq.