S.D. Codified Laws § 31-2-33
The Department of Transportation shall be authorized to cooperate with any other state, group of states, federal agency, or nationally recognized research organization and share in the expense of setting up, maintaining and operating research projects including test roads at any place within or without the State of South Dakota for the development of facts and criteria capable of being used in the design and construction of highways, highway surfaces, and highway structures, and for the establishment of an engineering basis for the enactment of adequate and equitable legislation governing the allowable loading and method of taxation; to provide information as to types and capacities of highway vehicles which are practicable to be used in highway transportation; to procure special information concerning engineering problems, costs of maintaining highways at different capacities, the necessity for increased taxation to cover costs of highway capacities; and to produce reliable information as to how to realize the most efficient and economical vehicle capacities consistent with optimum over all highway transportation.
SDCL 31-2-33