Helmets must be worn by everyone. Roads in the state are not opened unless indicated they are a joint use. They are mainly Township roads in sparsely populated areas. Same rule applies to road shoulders. You may legally ride in ditches.
Speed limits are what is posted for that road if it is a joint use road.
Youths between the ages of 10 and 16 must have a Safety Course and must carry the Certificate with them at all times showing they passed. South Dakota There are 1,052 miles of groomed trails in South Dakota. Trail permits are not required. Liability Insurance is mandatory for all snowmobiles. Helmets are not required.