S.C. Code Ann. § 56-5-3830: Driving through defiles or canyons or on mountain highways.

The driver of a motor vehicle traveling through defiles or canyons or on mountain highways shall hold the vehicle under control and as near the right-hand edge of the roadway as reasonably possible and, except when driving entirely to the right of the center of the roadway, shall give audible warning with the horn of the vehicle upon approaching any curve where the view is obstructed within a distance of two hundred feet along the highway.