S.C. Code Ann. § 56-5-1850: When passing on the right is permitted.

(a) The driver of a vehicle may overtake and pass upon the right of another vehicle only under the following conditions:

1. When the vehicle overtaken is making or about to make a left turn.

2. Upon a roadway with unobstructed pavement of sufficient width for two or more lines of vehicles moving lawfully in the direction being travelled by the overtaking vehicle.

(b) The driver of a vehicle may overtake and pass another vehicle upon the right only under conditions permitting such movement in safety. Such movement shall not be made by driving off the roadway.