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Truck and trailer rules in South Dakota: commercial vehicle line, trailer brakes, size and weight limits

What South Dakota Codified Laws say about the commercial motor vehicle line at 26,001 pounds, the all-wheel brake exemption for trailers of 3,000 pounds or less, the 102 inch width, 14 foot height, 45 foot single vehicle length and axle and gross weight.

Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.

This page reports what the official source says. It is not legal advice: ask the office named here. The sources are South Dakota Codified Laws published by the South Dakota Legislature: chapter 32-12A on commercial driver licences, chapter 32-18 on brakes and chapter 32-22 on size, weight and load. Federal background and the other places are on the parent page, trucks and trailers for tree work.

At a glance

ItemWhat the sources say
Commercial motor vehicle26,001 pounds or more rating, or a towed unit over 10,000 pounds; 16 or more passengers; any size carrying placarded hazardous materials
Licence classesNot set in the sections read
Trailer brakesRequired; all-wheel brakes waived at 3,000 pounds gross or less
Width, height102 inches wide; 14 feet high
Length45 feet single vehicle; 53 foot semitrailer on listed roads
Weight20,000 pounds single axle; 34,000 pounds tandem; 80,000 pounds on the interstate

The commercial vehicle line

Section 32-12A-1 defines a commercial motor vehicle as one designed or used to carry passengers or property with a combination rating of 26,001 pounds or more where the towed unit is rated over 10,000 pounds, or a vehicle rating of 26,001 pounds or more, or a vehicle designed for 16 or more passengers including the driver, or a vehicle of any size that must be placarded for hazardous materials. Section 32-12A-12 allows a commercial learner permit from age 18 for holders of a valid operator licence, for no more than one year. See section 32-12A-1 on definitions and section 32-12A-12 on the learner permit.

Brakes

Section 32-18-1 requires brakes meeting the chapter on every motor vehicle, trailer, semitrailer, pole trailer and combination on a highway. Section 32-18-3 says a trailer with a maximum gross weight of 3,000 pounds or less need not have brakes on all wheels, provided the trailer weight does not exceed 40 percent of the towing vehicle gross weight and the combination can meet the stopping standards in section 32-18-8. That section requires service brakes to stop a vehicle or combination from 20 miles per hour within set distances under any loading. See section 32-18-3 on the all-wheel exemption and section 32-18-8 on service brakes.

Width, height and length

Section 32-22-3 limits a vehicle or load to 102 inches wide, excluding required safety equipment. Section 32-22-14 limits height to 14 feet including the load, with 15 feet for trailers carrying baled feed. Section 32-22-5 limits a motor vehicle to 45 feet overall. Section 32-22-8.1 allows, on interstate and state trunk highways unless signed otherwise, a 53 foot semitrailer, 80 feet overall for a straight truck and trailer, and 28 1/2 feet per trailer in a road tractor and two trailer combination. Section 32-22-9 bars combinations of more than two units except as listed, and section 32-22-10 allows up to three units in listed forms, with breakaway brakes on the rear unit. See section 32-22-3 on width and section 32-22-8.1 on trailer length.

Weight

Section 32-22-16 sets 20,000 pounds on any one axle and 34,000 pounds on a tandem axle, plus a group limit from a formula in section 32-22-16.1, W = 500 [LN/(N-1) + 12N + 36]. On the interstate, gross weight may not exceed 80,000 pounds. Section 32-22-21 also limits weight per inch of tire width, at 600 pounds per inch on dual tire axles and steering axles. See section 32-22-16 on axle and gross weight.

Sources