Truck and trailer rules in South Carolina: licence classes, trailer brakes, safety chains, size and weight limits

This page reports what the official source says. It is not legal advice: ask the office named here. The sources are three titles of the Code of Laws of South Carolina, published on the South Carolina Legislature website: chapter 1 of Title 56 on driver licensing, chapter 3 on registration and chapter 5 on the Uniform Act regulating traffic. Federal background and the other places are on the parent page, trucks and trailers for tree work.

At a glance

Item	What the sources say
Commercial motor vehicle	Gross vehicle weight rating of 26,001 pounds or more; 16 or more persons; or placarded hazardous materials
Class A	Combination rated 26,001 pounds or more when the towed vehicle is rated over 10,000 pounds
Class B	Single vehicle rated 26,001 pounds or more, or one towing a vehicle rated 10,000 pounds or less
Basic licence	Vehicles and combinations that do not exceed 26,000 pounds gross vehicle weight rating
Trailer brakes	Brakes on all wheels of a trailer over 3,000 pounds gross weight, applied automatically on breakaway and held at least fifteen minutes
Safety chain	Required in addition to the regular hitch; not for a fifth wheel and kingpin
Width, height	102 inches wide; 13 feet 6 inches high
Length	40 feet for a motor vehicle; 53 feet for a trailer or semitrailer in a combination
Gross weight	35,000 pounds two-axle single unit; 46,000 pounds three axles; 80,000 pounds maximum on the interstate by formula
Trailer registration fee	US$20 every two years for a trailer not exempted

Licence classes

Section 56-1-2030 defines a commercial motor vehicle as one designed or used to carry passengers or property that has a gross vehicle weight rating of 26,001 pounds or more, is designed to carry 16 or more persons including the driver, or carries hazardous materials that must be placarded. Section 56-1-2100 sets the classes. Class A is a combination with a gross combination weight rating of 26,001 pounds or more where the towed vehicle is rated over 10,000 pounds. Class B is a single vehicle rated 26,001 pounds or more, or one towing a vehicle rated 10,000 pounds or less. Class C is a single vehicle or combination that is neither of those but is designed for 16 or more passengers or must be placarded. Section 56-1-130 says a basic driver's licence covers motor vehicles and combinations that do not exceed 26,000 pounds gross vehicle weight rating, and a classified licence with endorsements covers heavier vehicles. The same chapter says a person driving a commercial motor vehicle without the proper class and endorsements must be placed out of service and is guilty of a misdemeanor. See Title 56 chapter 1 on driver licensing.

Trailer brakes and safety chains

Section 56-5-4850 says every motor vehicle, trailer, semitrailer and pole trailer, and any combination, must have brakes that comply with the chapter. Service brakes must be adequate to control, stop and hold the vehicle under all conditions of loading and on any grade, and parking brakes must hold it on any grade. A vehicle made after June 7, 1949 must have brakes on all wheels, with an exception for a trailer of gross weight not over 3,000 pounds, provided the wheels' total weight does not exceed 40 percent of the gross weight of the towing vehicle and the combination can meet the stopping performance in section 56-5-4860. Subsection (d) says every trailer, semitrailer and pole trailer with air or vacuum brakes, and every one with a gross weight over 3,000 pounds, must have brakes on all wheels that apply automatically and promptly on breakaway from the towing vehicle and stay applied for at least fifteen minutes. A towing vehicle made after July 1, 1964 must be able to stop with its service brakes if the towed vehicle breaks away.

Section 56-5-5150 says a towing vehicle must be attached to the towed vehicle by a safety chain, cable or equivalent device in addition to the regular drawbar, tongue, hitch or other connection, strong enough to keep the towed vehicle connected under all conditions. It does not apply to a fifth wheel and kingpin assembly. Section 56-5-4120 limits the drawbar or other connection to 15 feet between vehicles, apart from vehicles carrying poles, pipe, machinery or other structural objects that cannot readily be taken apart, and requires a white flag or cloth at least 12 inches square on a chain, rope or cable connection. See Title 56 chapter 5 on traffic regulation.

Width, height, length and loads

Section 56-5-4030 says the total outside width of a vehicle or its load may not exceed 102 inches, not counting safety devices the Department of Public Safety approves. Section 56-5-4060 says no vehicle, unladen or loaded, may exceed 13 feet 6 inches in height, with a 14 foot exception for automobile transporters and certain saddle mount combinations. Section 56-5-4070 says a motor vehicle may not exceed 40 feet overall including bumpers and load, with exceptions for buses and motor homes, and a trailer or semitrailer in a two unit combination on the interstate and listed highways may not exceed 53 feet. Section 56-5-4080 says a load may not extend more than three feet past the front of the vehicle or six feet past the rear of the bed or body.

Section 56-5-4100 says no vehicle may be driven unless it is built or loaded to prevent its load from dropping, sifting, leaking or escaping, and that a load and any covering must be securely fastened so it does not become loose or a hazard to other highway users. A person from whose vehicle cargo has fallen must make every reasonable effort to clean the highway and pay the cost.

Weight

Section 56-5-4140 sets maximum gross weight for a vehicle or combination: 35,000 pounds for a single unit with two axles, 46,000 pounds with three axles, 63,500 pounds with four axles and 65,000 pounds with five or more; for combinations, 50,000 pounds with three axles, 65,000 pounds with four and 73,280 pounds with five or more. On the interstate, vehicles over 75,185 pounds may go up to 80,000 pounds under a bridge formula, and a single axle on the interstate may not exceed 20,000 pounds. A ten percent enforcement tolerance applies to the limits, and fifteen percent on non-interstate routes for unprocessed forest products. Section 56-5-4160 sets the fine for overweight at five cents per pound for axle overweight, and a scale of four, six or ten cents per pound for gross overweight by band.

Trailer registration

Section 56-3-700 sets a biennial registration fee of US$20 for every trailer, semitrailer or pole trailer designed for carrying property that is not exempted, and excludes house trailers, utility trailers and boat trailers, which are covered elsewhere. See Title 56 chapter 3 on registration.