S.D. Codified Laws § 32-20-12.1
Notwithstanding the provisions of § 32-20-12, the Transportation Commission or any board of county commissioners by ordinance may prohibit the operation of off-road vehicles in any highway ditch along any section of highway under its jurisdiction. However, neither the Transportation Commission nor any board of county commissioners may prohibit an off-road vehicle from crossing one side of the highway to the other. This section does not affect off-road vehicles used in normal agricultural operation or service vehicles of any utility while in the line of duty for the utility. For the purposes of this section, the term, utility, means any provider of electric, gas, water, sewer, pipeline, or telecommunications service.
Notice of any restriction made pursuant to this section shall be given by placing and maintaining regulatory signs at each end of the section of highway and at each point of intersection. The signs shall be of substantial construction which conspicuously indicates the restriction.
SDCL 32-20-12.1