S.D. Codified Laws § 32-22-12.1
The provisions of §§ 32-22-9 to 32-22-11, inclusive, do not apply to a combination of vehicles consisting of a towing motor vehicle and two trailers which conform to the specifications contained in this section. In such a combination, the first trailer shall be connected to the towing vehicle by a ball hitch, a gooseneck hitch, pintle hitch or a fifth wheel hitch. The hitch connecting the second trailer to the first trailer shall be a ball type hitch, gooseneck hitch or a pintle hitch directly fastened to the frame of the first trailer. The second trailer may not exceed twenty-four feet in length and if the gross weight of the second trailer is greater than three thousand pounds, it shall be equipped with breakaway brakes. The maximum length of the vehicles in this combination may not exceed seventy-five feet. A violation of this section is a Class 2 misdemeanor.
The Transportation Commission may by rules adopted pursuant to chapter 1-26 prohibit or restrict the use of the combination of vehicles described in this section on any highway where such combination of vehicles would create a safety hazard.
SDCL 32-22-12.1