Truck and trailer rules in Maine: licence classes, 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 chapters of Title 29-A, Motor Vehicles and Traffic, of the Maine Revised Statutes, published on the Maine Legislature website: chapter 11 on the driver's licence, chapter 17 on equipment and chapter 21 on weight, dimension and protection of ways. The copies read were generated on October 5, 2026. 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
Class A	Combination rated 26,001 pounds or more when the vehicle or vehicles towed are over 10,000 pounds
Class B	Single motor vehicle rated 26,001 pounds or more, or one towing a vehicle of 10,000 pounds or less
Class C	Single vehicle or combination that is neither; a commercial licence only with an endorsement
Brakes	Adequate brakes on all wheels of all axles of a truck or trailer; exception for a trailer or semitrailer up to 3,000 pounds gross weight
Safety chain	Chain or steel cable of not less than 1/4-inch wire, in addition to the tow bar or coupling
Width, height	102 inches wide; 13 feet 6 inches high
Length	45 feet for a vehicle; 65 feet for a combination, with listed exceptions
Gross weight	34,000 pounds two axles; 54,000 pounds three axles; 69,000 pounds four axles; 80,000 pounds for combinations of five or more axles

Licence classes

Section 1253 of chapter 11 says a Class A or Class B licence, or a Class C licence carrying an endorsement, is a commercial licence, and that the State must follow the federal Commercial Motor Vehicle Safety Act of 1986 and the Motor Carrier Safety Improvement Act of 1999, with the federal rule prevailing in a conflict. Section 1252 sets the classes. A Class A licence is for a combination with a gross vehicle weight rating of 26,001 pounds or more where the gross vehicle weight rating or weight of the vehicles being towed is over 10,000 pounds. A Class B licence is for a single motor vehicle rated 26,001 pounds or more, or one towing a vehicle rated or weighing 10,000 pounds or less. A Class C licence is for a single vehicle or combination that does not meet the Class A or Class B definition. See chapter 11 on the driver's licence.

Brakes and safety chains

Section 1902 says a motor vehicle must have adequate brakes in good working order that are sufficient to control it. A four-wheel brake vehicle must be adjusted to stop within 30 feet from 20 miles per hour, and the parking brakes must hold the vehicle on any grade under all conditions of loading. Subsection 4 says special mobile equipment, a truck, truck tractor, trailer or semitrailer must have adequate brakes acting on all wheels of all axles, except a trailer or semitrailer not exceeding a gross weight of 3,000 pounds, a vehicle towed by a wrecker, a vehicle that meets the federal motor carrier safety brake requirements, and certain reel trailers and pole dollies of 12,000 pounds or less. See chapter 17 on equipment.

Section 2385 of chapter 21 covers protruding objects and trailers. Subsection 3 says a trailer, semitrailer or towed vehicle must have a safety chain or steel cable besides the tow bar or coupling device, attached against breakaway from the towing vehicle and made of not less than 1/4-inch wire. It does not apply to truck tractor and semitrailer units with a fifth wheel. The section also sets a red light at night or a clean fluorescent cloth at least 12 by 12 inches by day on a projecting load, and a red reflector on logs that project more than 4 feet from the rear.

Width, height and length

Section 2380 says a vehicle wider than 102 inches over all may not be operated on a public way or bridge, with listed fittings of up to 3 inches left out of the measurement on a commercial motor vehicle. A vehicle with a structural part more than 13 feet 6 inches high may not be operated, and a load may not extend more than 6 inches above the maximum permissible structural height. Section 2390 says a vehicle may not exceed 45 feet, except as the section provides, and a combination of vehicles may not exceed 65 feet unless otherwise permitted by law. A trailer or semitrailer may be 45 to 48 feet in structural length only if the distance between the rearmost axle centres of the tractor and trailer does not exceed 38 feet. A combination carrying tree-length logs exclusively may have the load extend rearward beyond the body by no more than 8 1/2 feet, with no more than 25 percent of the log length beyond the body and a total vehicle and load length of no more than 74 feet.

Weight

Section 2352 says a vehicle may not be operated on a public way if its weight exceeds a gross vehicle weight of 100,000 pounds, its registered weight with a tolerance of 500 pounds or 2 1/2 percent over, whichever is greater, or the weight limits on its axle configuration. Section 2353 sets gross vehicle weight limits of 34,000 pounds for a two-axle vehicle, 54,000 pounds for a three-axle vehicle or combination, 69,000 pounds for a four-axle vehicle or combination and for single unit vehicles of five or more axles except as section 2364 provides, 80,000 pounds for combinations with five or more axles, and 100,000 pounds for a three-axle truck tractor with a tri-axle semitrailer. It reduces the limit for a four-axle combination by 1,000 pounds for each foot under 18 feet between the extreme axle centres. See chapter 21 on weight, dimension and protection of ways.