S.D. Codified Laws § 32-26-20
The Department of Transportation or local authorities in their respective jurisdictions may modify the method of turning at intersections provided by §§ 32-26-17 and 32-26-18 by clearly indicating by buttons, markers, or other direction signs installed within an intersection the course to be followed by vehicles turning thereat. It is a Class 2 misdemeanor for any driver to fail to turn in a manner as so directed. No such signs or buttons shall be placed upon any state highway without the approval of the Department of Transportation. When an intersection is so constructed and laid out that different and clearly defined courses of travel are provided for vehicles turning to the left or right, as the case may be, it shall be lawful for any driver in making any such turn to follow the course thereby indicated.
SDCL 32-26-20