Truck and trailer rules in Minnesota: licence classes, brakes, size limits and intrastate carrier rules

This page reports what the official source says. It is not legal advice: ask the office named here. The sources are five sections of the 2025 Minnesota Statutes published by the Office of the Revisor of Statutes. The agencies named in them are the Department of Public Safety for licences and the Department of Transportation for carrier rules. Federal background and the other places are on the parent page, trucks and trailers for tree work.

At a glance

Item	What the statutes say
Class D	Single-unit vehicles up to 26,000 pounds, with towing limits
Class B, Class A	Class B: single-unit vehicles; Class A: any vehicle or combination
Trailer brake weight	Brakes on a trailer with a gross vehicle weight of 3,000 pounds or more
Breakaway	Brakes that stop and hold a trailer over 3,000 pounds when it detaches
Width	102 inches
Length	45 feet single vehicle, 48 feet for mobile cranes; combination 75 feet
Carrier rules	Intrastate carriers follow the federal parts the statute incorporates

Licence classes and towing

Section 171.02 sets four general classes. Class D covers all single-unit vehicles except those with a gross vehicle weight over 26,000 pounds, vehicles built to carry more than 15 passengers including the driver, and vehicles carrying hazardous materials. Within the Class D paragraph the statute allows towing if the towed vehicles weigh 10,000 pounds or less, or if they weigh more than 10,000 pounds and the combination is 26,000 pounds or less. Class B covers all single-unit vehicles and towing only vehicles of 10,000 pounds or less. Class A is valid for any vehicle or combination. A motorcycle, school bus, tank vehicle, double or triple trailer combination, hazardous materials vehicle or bus needs an endorsement. See section 171.02 on licence types.

Trailer brakes and breakaway

Section 169.67 says no trailer or semitrailer with a gross vehicle weight of 3,000 pounds or more, or a gross weight that exceeds the empty weight of the towing vehicle, may be drawn on a highway unless it has brakes adequate to control, stop and hold it. A surge brake meets the requirement. No trailer or semitrailer with a gross vehicle weight of more than 3,000 pounds may be drawn unless its brakes are constructed to stop and hold it whenever it becomes detached from the towing vehicle. Another paragraph excuses a motor vehicle drawn by another motor vehicle with qualifying brakes, up to 3,000 pounds gross behind a passenger automobile other than a pickup and 12,000 pounds behind any other motor vehicle.

Subdivision 4 requires foot brakes on all wheels of motor vehicles, trailers and semitrailers manufactured after June 30, 1988. It excepts a mobile crane that is not operated over 45 miles per hour and can meet the stopping standards, and a trailer or semitrailer with a gross weight of less than 3,000 pounds. The section does not mention safety chains. See section 169.67 on brakes.

Width, height and length

Section 169.80 sets a total outside width of 102 inches for a vehicle or load, exclusive of rearview mirrors or load securement devices that are not an integral part of the vehicle and do not exceed three inches on each side. A low bed trailer or equipment dolly used only for farm machinery and construction equipment may be up to nine feet wide, and one over 102 inches may not run on an interstate highway without a permit under section 169.86. It must show 12-inch square red flags at the front and rear of the left side. The size and weight sections do not apply to a vehicle under a special permit. See section 169.80 on size, weight and load.

Section 169.81 sets a height of 13 feet six inches. A single vehicle may not exceed 45 feet overall, except that mobile cranes may be 48 feet. A single trailer may not exceed 45 feet including the tow bar. A semitrailer may not exceed 48 feet, or up to 53 feet if the distance from the kingpin to the centreline of the rear axle group is 43 feet or less. A combination may have no more than two units, with listed exceptions, and may not exceed 75 feet in total, with the limit not applying to combinations carrying telephone, electric light and power poles, piling or pole-length pulpwood. See section 169.81 on height and length.

Federal safety rules for intrastate carriers

Section 221.0314 says intrastate motor carriers must follow the federal regulations it incorporates, and that a reference to a federal agency means the Minnesota Department of Transportation. Part 391 on driver qualification is incorporated except listed sections, and drivers in intrastate transportation must be at least 18. Driver qualification files stay at the carrier's principal place of business while the driver is employed and for three years after. Part 392 on driving and Part 393 on parts and accessories are incorporated, and a lightweight vehicle must carry a fire extinguisher meeting section 393.95. Part 395 on hours of service is incorporated except several paragraphs of section 395.1, and it does not apply to drivers of lightweight vehicles. Part 396 is incorporated except sections 396.9, 396.17, 396.19, 396.21 and 396.23 and section 396.11, paragraph (a), clause (5); the excepted sections include the federal periodic inspection rule. The page read does not define lightweight vehicle and does not name a state carrier number. See section 221.0314 on federal safety regulations.