Mass. Gen. Laws ch. 90 § 19
Except as otherwise provided in sections nineteen F and nineteen G, or when a vehicle has been authorized by permit to transport an irreducible load, the following provisions shall apply:
No motor vehicle or trailer, the outside width of which is more than one hundred and two inches or the extreme overall length of which is more than thirty-three feet, or in the case of a truck, or house trailer, 40 feet, or, in the case of a motor bus or auto home, 45 feet, or in the case of an articulated bus, sixty feet, or in the case of a traditional automobile transporter, a traditional boat transporter and a truck-trailer boat transporter, sixty-five feet not including load overhang which shall not exceed three feet beyond the foremost part of the front transporting vehicle or more than four feet beyond the rear bed of the body, or in the case of a stringer-steered automobile transporter or stringer-steered boat transporter, seventy-five feet not including load overhang which shall not exceed three feet beyond the foremost part of the front transporting vehicle or more than four feet beyond the rear bed of the body, or in the case of a semi-trailer in a semi-trailer unit or trailer in a tractor-trailer unit, 53 feet, or in the case of a semi-trailer or trailer in tandem unit, twenty-eight feet, or in the case of semi-trailers in a B-train assembly unit, twenty-eight feet, such a length being exclusive of the B-train assembly when being used between the first and second semi-trailer, but the B-train assembly is to be included in the length measure of the semi-trailer when no second semi-trailer is mounted on the B-train assembly with the length limitation of the semi-trailer to be forty-eight feet in that instance, or in the case of a driveaway saddlemount with fullmount vehicle transporter combination including double and triple saddlemount combinations conforming to safety regulations at 49 CFR 393.71, seventy-five feet, shall be operated on any way without a special permit so to operate from the board or officer having charge of such way, or in the case of a state highway or a way determined by the department of highways to be a through route, from said department. The lengths of semi-trailers or trailers operating under the provisions of this section shall be inclusive of load-holding devices and exclusive of safety devices without load-holding capacity. The overall length of any vehicle and trailer combination or semi-trailer combination or any driveaway saddlemount vehicle or fullmount vehicle transporter combination authorized to operate under this section shall not exceed sixty feet or, in the case of a house trailer and tow vehicle combination authorized by this section, 65 feet except as otherwise specifically authorized by this section or authorized by special permit as aforesaid; provided, however that no overall length limitation shall apply to semi-trailer units or tractor-trailer units when the trailer or semi-trailer in such units does not exceed 53 feet, or to tandem units or B-train assembly units when the trailer or semi-trailer in such units does not exceed twenty-eight feet. The one hundred and two inches width provided in this section shall be exclusive of load-induced tire bulge, rearview mirrors, turn signal lamps, shade awnings on auto homes and house trailers, hand-holds for cab entry and egress and splash and spray suppressant devices; provided, however, that such mirrors and other devices are mounted so as not to cause a hazard to pedestrians on or adjacent to any way. Other safety devices which the department determines are necessary for the safe and efficient operation of motor vehicles shall not be included in the calculation of the one hundred and two inches width specified in this section; provided, however, that such other safety devices may be so mounted and so extend beyond the permitted width only in such manner and to such extent as determined by the department, but in no event shall such safety device extend more than three inches beyond the maximum vehicle width on each side. For the purposes of this section, all appurtenances at the front or rear of a commercial motor vehicle, semi-trailer, or trailer, whose functions relate to the safe and efficient operation of such vehicle, semi-trailer, or trailer, shall be excluded from the length computation of such vehicle, semi-trailer or trailer; provided, however, that such appurtenances shall not be designed or used for carrying cargo. Notwithstanding the provisions of this section authorizing operation of vehicles on ways within the commonwealth, the department for specific safety reasons, may declare individual ways, unavailable for through-route travel by particular vehicles, provided signs are erected to indicate such vehicle exclusions.
Notwithstanding other provisions of this section, the combined overall length of a pole dolly or pole dickey and the load being carried thereon may, while being used for transportation of poles or single units of lumber or metal, exceed forty-eight feet, but the overall length when considered in combination with the motor vehicle accompanying it shall not exceed sixty-five feet or, in the case of an electric company as defined in chapter one hundred and sixty-four, seventy-five feet, without a special permit as provided for in this paragraph.
Notwithstanding the provisions of this section, no passenger motor vehicle shall be operated on any way if such vehicle has the side wall or thread of any tire projecting outward beyond the outer portion of the fender or side body panel, unless such vehicle is equipped with four-wheel drive or is otherwise modified and intended for off-the-way use. No vehicle shall exceed a height of thirteen feet six inches, except that a special permit may be issued by the board or officer having charge of the ways for the operation of a vehicle of a height in excess of this limitation. The aforesaid dimensions of width, length and height shall be inclusive of the load and load-holding devices. No motor vehicle registered under the provisions of this chapter which has a total height exceeding ten feet, excluding the height of any load thereon shall be operated on any way unless such total height is painted or printed in letters and numerals at least four inches high in a conspicuous place upon the side or front of such vehicle. The foregoing limitations on length shall not apply to any vehicle or combination of vehicles being towed because of disablement or emergency. Except as provided in this section, no trailer which with its load weighs more than five thousand pounds, other than a semitrailer, a heavy duty platform trailer, a cable-reel trailer, a house trailer, a trailer having at least two axles and used to collect and carry bulk milk from dairy farms to processing plants, a trailer which is an apparatus or other object on wheels not used to transport other things for delivery, or a trailer having at least two axles which, when used for agricultural purposes with its load weighs not more than ten thousand pounds; provided, however, that the gross weight of such vehicle as operated does not exceed the gross vehicle weight rating as established by the original manufacturer of the trailer, shall be operated or drawn on any way without a permit so to operate from the board or officer having charge of such way or, in case of a state highway or a way determined by the department to be a through route, from said department. Any motor vehicle, trailer or other vehicle which carries a crane, or boom whether or not permanently or temporarily attached to said vehicle or trailer shall, if such crane or boom extends more than four feet beyond the bed or body of such vehicle or trailer, display at the extreme rear end of such crane or boom a red light or red flag or cloth in the manner provided in section seven; provided, however, that if such crane or boom extends more than fifteen feet beyond the bed or body of such vehicle or trailer, such vehicle or trailer shall not be operated or drawn on any way unless another vehicle follows immediately behind the projecting extremity of such crane or boom for the purpose of protecting other vehicles approaching from the rear. A trailer which with its load weighs not more than six thousand pounds, or farm machinery or implement which exceeds the maximum width dimensions aforementioned, may be operated, drawn or carried upon any way, if such trailer, farm machinery or implement is used exclusively for agricultural purposes, but this provision shall not prevent any trailer, farm machinery or implement, if used exclusively for such purposes, from being operated without registration upon any way in the manner provided in section nine. A trailer which with its load weighs more than three thousand pounds may be operated or drawn upon any way for a distance not exceeding three hundred yards, if such trailer is used for industrial purposes other than agricultural purposes, for the purpose of going from property owned or occupied by the owner of such trailer to other property so owned or occupied. Unless otherwise specifically authorized by law, no motor vehicle shall be operated on any way to draw more than one trailer or other vehicle without a permit so to operate from the department of highways.
Mass. Gen. Laws ch. 90, § 19