S.C. Code Ann. § 56-3-740

For every trackless trolley bus the biennial registration fee is four hundred dollars for each bus weighing not over fifteen thousand pounds, exclusive of passengers, and for each bus weighing more than fifteen thousand pounds, exclusive of passengers, an additional forty dollars for each additional one thousand pounds of weight or fraction. The Department of Motor Vehicles must include under this classification every bus propelled by electric power obtained from overhead trolley wires but not operated upon rails.