S.C. Code Ann. § 56-5-1810
(a) Upon all roadways of sufficient width a vehicle shall be driven upon the right half of the roadway except as follows:
1. When overtaking and passing another vehicle proceeding in the same direction under the rules governing such movement.
2. When an obstruction exists making it necessary to drive to the left of the center of the highway. Any person so doing shall yield the right-of-way to all vehicles traveling in the proper direction upon the unobstructed portion of the highway within such distance so as not to constitute an immediate hazard.
3. Upon a roadway divided into three marked lanes for traffic under the rules applicable thereon.
4. Upon a roadway restricted to one-way traffic.