S.D. Codified Laws § 32-20B-9
For purposes of this chapter, the term, electric bicycle, means a bicycle or a tricycle that is equipped with a seat or saddle, with operable pedals for propulsion, and with an electric motor of seven hundred fifty watts or less.
An electric bicycle is a Class I electric bicycle if the motor provides assistance only when the person is pedaling and ceases to provide assistance when a speed of twenty miles per hour is achieved.
An electric bicycle is a Class II electric bicycle if the motor is capable of propelling the bicycle without the person pedaling and ceases to provide assistance when a speed of twenty miles per hour is achieved.
An electric bicycle is a Class III electric bicycle if the motor provides assistance only when the person is pedaling and ceases to provide assistance when a speed of twenty-eight miles per hour is achieved.
SDCL 32-20B-9