S.D. Codified Laws § 32-3-53.4
Trailer defined
For the purposes of §§ 32-3-53 and 32-3-53.2 , a trailer is any trailer as defined in § 32-3-1 which has an actual weight of three thousand pounds or greater.
Source: SL 1985, ch 239, § 8; SL 2011, ch 138, § 1.