Truck and trailer rules in Massachusetts: licence line, 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 sections of the Massachusetts General Laws published by the Massachusetts Legislature: chapter 90F on commercial driver licensing, chapter 90 on motor vehicles and chapter 85 on highways. 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	Used in commerce with a gross vehicle weight rating of 26,001 pounds or more, or a lesser federal rating; more than 16 passengers; placarded hazardous materials
Licence classes	Not set in the sections read; chapter 90F points to 49 CFR part 383 for the vehicles covered
Brakes	Air or hydraulic power brakes on a motor vehicle over 10,000 pounds unladen; air or electric brakes on a trailer or semi-trailer over 10,000 pounds unladen
Safety chains	Every trailer except a semi-trailer, in addition to the hitch
Width, height	102 inches wide; 13 feet 6 inches high
Length	33 feet motor vehicle or trailer; 40 feet truck; 53 feet semi-trailer; 60 feet vehicle and trailer combination
Weight	46,000 pounds two axles; 80,000 pounds three or more axles; 22,400 pounds on an axle, all without a permit

The commercial vehicle line

Chapter 90F, section 1, defines a commercial motor vehicle as a motor vehicle used in commerce, designed or used to carry passengers or property, with a gross vehicle weight rating of 26,001 pounds or more or a lesser rating set by federal regulation. It also covers a vehicle designed to carry more than 16 passengers including the driver, and one that carries hazardous materials requiring placards under 49 CFR part 172, subpart F. For the purposes of section 9 the term includes any vehicle described in 49 CFR 383.5 and in the registrar's regulations adopting the federal rules. The sections of chapter 90F read here do not list licence classes. See chapter 90F section 1 on definitions.

Brakes and safety chains

Chapter 90, section 7, requires every motor vehicle to have brakes adequate to control it, kept in good working order and meeting the registrar's rules. An automobile needs two braking systems, a service brake and a parking brake, each with its own means of application and each working on at least two wheels. Except for a school bus or fire apparatus, every motor vehicle and every tractor made for drawing another vehicle that weighs more than 10,000 pounds unladen must have full air brakes, or hydraulic brakes with vacuum or air power assist. Every trailer or semi-trailer weighing more than 10,000 pounds unladen must have air or electric brakes. A trailer of 3,000 pounds gross or less that does not hide the towing vehicle's lights needs only one rear red light and one white plate light.

The same section says every trailer except a semi-trailer must have safety chains as well as a regular hitch, so that it cannot break away from the towing vehicle, and the chains must meet the registrar's minimum standards. A commercial motor vehicle, semi-trailer or trailer in interstate commerce that conforms to the federal motor carrier equipment rules is deemed to conform to the section. A load or object that reaches four feet or more past the cab or body must show a red light at its rear end, or a red flag or cloth of at least 12 inches square when lights are not required. See chapter 90 section 7 on brakes and equipment.

Width, height and length

Chapter 90, section 19, says no motor vehicle or trailer wider than 102 inches may run on a way without a special permit from the board or officer in charge of the way. Mirrors, turn signal lamps, load-induced tire bulge, hand-holds and spray suppressant devices are left out of the 102 inches, and other safety devices the department approves may extend no more than three inches on each side. Length limits are 33 feet for a motor vehicle or trailer, 40 feet for a truck or house trailer, 45 feet for a motor bus, 53 feet for a semi-trailer in a semi-trailer unit or a trailer in a tractor-trailer unit, and 28 feet for a trailer in a tandem unit. A vehicle and trailer combination may not exceed 60 feet overall unless the section says otherwise. No vehicle may exceed 13 feet 6 inches, and the dimensions include the load and load-holding devices. A registered motor vehicle taller than 10 feet, leaving out its load, must show its total height in letters and numbers at least four inches high on the side or front.

The section has a rule for a vehicle or trailer that carries a crane or boom. If the crane or boom reaches more than four feet past the bed or body, a red light, flag or cloth must be shown at its extreme rear end. If it reaches more than 15 feet past the bed or body, the vehicle or trailer may not be operated on a way unless another vehicle follows immediately behind the projecting end. A trailer weighing more than 5,000 pounds with its load needs a permit unless it falls in a listed kind, such as a semitrailer or house trailer, and no motor vehicle may draw more than one trailer without a permit from the department of highways, unless law otherwise allows. See chapter 90 section 19 on dimensions and weights.

Weight

Chapter 90, section 19A, says a motor vehicle with two axles that weighs no more than 46,000 pounds with its load, and a vehicle or unit with three or more axles that weighs no more than 80,000 pounds, may travel on a public way without the permit that chapter 85, sections 30 and 30A, would otherwise require. That holds only if no axle, measured at the ground, carries more than 22,400 pounds, or 18,000 pounds where axles are spaced less than six feet apart, and the gross weight on a group of axles stays within a formula in the section. Two consecutive sets of tandem axles may carry 34,000 pounds each if the distance between the first and last axles is at least 36 feet. An officer may direct a driver to the nearest scales within five miles.

Chapter 85, section 30, sets a permit rule. It requires a permit for a vehicle weighing more than 14 tons, or 15 tons with pneumatic tires, with no permit for a three-axle vehicle of 20 tons or less, and for a weight of more than 800 pounds on any inch of tire outside the metropolitan parks or sewerage districts. See chapter 90 section 19A on weight limitations and chapter 85 section 30 on heavy vehicles.