S.C. Code Ann. § 56-5-4070 – Length of vehicles; limitations on vehicle combinations

(A) Two or three unit vehicle combinations may be operated on the National System of Interstate and Defense Highways, on those qualifying federal-aid highways so designated by the United States Secretary of Transportation, and on other highways as designated by the Department of Transportation in accordance with Section 56-5-4075. The department may require warning devices which may be necessary to protect public safety. When in use on the National System of Interstate and Defense Highways and "other qualifying highways":
1. (1) No trailer or semitrailer may be operated in a two unit truck tractor-trailer or truck tractor-semitrailer combination in excess of fifty-three feet, inclusive of the load carried on it. A fifty-three foot long trailer must be equipped with a rear underride guard, and the distance between the kingpin of the vehicle and the center of the rear axle assembly or to the center of the tandem axle assembly if equipped with two axles may be no greater than forty-one feet.
2. (2) A trailer or semitrailer, operating in a three unit combination, may not exceed a length of twenty-eight and one-half feet, inclusive of the load carried on it.
3. (3) Auto and boat transporters may not have an overall length in excess of seventy-five feet, exclusive of front and rear overhang. However, front overhang may not exceed three feet, and rear overhang may not exceed four feet.
4. (4) Saddle mounts and full mounts may not have an overall length in excess of seventy-five feet.
(B) No motor vehicle, exclusive of truck tractors being used in two or three unit combinations on the National System of Interstate and Defense Highways, on those qualifying federal-aid highways so designated by the United States Secretary of Transportation, and on other highways as designated by the Department of Transportation in accordance with Section 56-5-4075, may exceed a length of forty feet extreme overall dimension, inclusive of front and rear bumpers and load carried on it, except buses as approved by the department, or motor homes which may not exceed forty-five feet in length, if the turning radius of the motor home is forty-eight feet or less.
(C) A combination of vehicles coupled together or especially constructed to transport motor vehicles in a truckaway or driveaway service may tow up to three saddle mounts. No other combination of vehicles coupled together may consist of more than two units, except as permitted by subsection (A).
(D) Except as permitted by subsection (A), trailers or semitrailers used within combinations may not exceed a length of fifty-three feet, and auto transporters are excluded from trailer length limitations. A fifty-three foot long trailer must be equipped with a rear underride guard, and the distance between the kingpin of the vehicle and the center of the rear axle assembly or to the center of the tandem axle assembly if equipped with two axles may be no greater than forty-one feet. Auto transporters may be allowed an upper level overhang not to exceed three feet on the front and four feet on the rear.
(E) Except where specifically prohibited in this article, there is no overall length limit on combination vehicles.
(F) Appropriate safety and energy conservation devices and compressors and fuel saving equipment on the front or loading devices on the rear of vehicles must not be considered when determining their length for purposes of this section if the overall length limitations of combinations of vehicles is not exceeded.