Mass. Gen. Laws ch. 90 § 7
Every motor vehicle operated in or upon any way shall be provided with brakes adequate to control the movement of such vehicle and conforming to rules and regulations made by the registrar, and such brakes shall at all times be maintained in good working order. Every automobile shall be provided with at least two braking systems, one of which shall be the service brake system, and the other shall be the parking brake system, each with a separate means of application, each operating directly or indirectly on at least two wheels and each of which shall suffice alone to stop said automobile within a proper distance as defined in said rules and regulations; provided, that if such systems are connected, combined or have any part in common, such systems shall be so constructed that a breaking of any one element thereof will not leave the automobile without brakes acting directly or indirectly on at least two wheels; and provided, further, that a tractor having a draw-bar pull rating of ten horse power or less and capable of a maximum speed of not more than eighteen miles an hour and designed specially for use elsewhere than on the traveled part of ways may be operated thereon if equipped with a single braking system which shall suffice to stop such tractor within a proper distance as aforesaid. Every automobile equipped with an hydraulic braking system whether or not assisted by other means, which provides braking action on four or more wheels, shall be equipped with a service brake system so arranged as to provide separate systems for at least two wheels and so designed and constructed that rupture or leakage-type failure of any single pressure component of the service brake system, except structural failures of the brake master cylinder body, effectiveness indicator body, or other housing common to the divided system, will not result in complete loss of function of the vehicle brakes when force on the brake pedal is continued. "Pressure component" means any internal component of the brake master cylinder or master control unit, wheel brake cylinder, brake line, brake hose, or equivalent, except vacuum assist components. Except in the case of a school bus or fire apparatus, every motor vehicle and every tractor which is designed and used for drawing another vehicle, having an unladen weight of more than ten thousand pounds, shall be equipped with full air brakes or hydraulic brakes with vacuum power assist or air power assist. All braking systems shall be constructed and designed so as to permit modulated control of brake application and release by the operator from the normal operating position. Every trailer or semi-trailer having an unladen weight of more than ten thousand pounds shall be equipped with air or electric brakes. One braking system shall be so constructed that it can be set to hold the automobile stationary. Each motorcycle shall have either a split service brake system or two independently actuated service brake systems. Any motorcycle which has a number or registration plate issued under the provisions of section six A of said chapter ninety or which was not manufactured with either a split service brake system or two independently actuated service brake systems, shall be required to have one brake system adequate to stop said motorcycle within a proper distance, as defined in rules and regulations made by the registrar. Every automobile used on a way by a person in giving driving instruction for compensation shall be equipped with dual brake controls whereby he may apply the brake while the pupil is driving. Every motor vehicle so operated shall be provided with a muffler or other suitable device to prevent unnecessary noise and with a suitable bell, horn or other means of signalling, with suitable lamps, and with a lock, key or other device to prevent such vehicle from being set in motion by unauthorized persons, or otherwise contrary to the will of the owner or person in charge thereof. Every automobile operated during the period from one half an hour after sunset to one half an hour before sunrise, and during any other period when visibility is reduced by atmospheric conditions so as to render dangerous further operation without lights being displayed, shall display at least two lighted white headlamps with at least one mounted at each side of the front of the vehicle or if parked within the limits of a way at least one white or amber light on the side of the automobile nearer the center of the way, and every motorcycle so operated at least one white headlamp and every such motorcycle with a sidecar attached, in addition, one such light on the front of the sidecar, and every motor truck, trailer and commercial motor vehicle used solely as such, having a carrying capacity of three tons or over, in addition, an amber light attached to the extreme left of the front of such vehicle, so attached and adjusted as to indicate the extreme left lateral extension of the vehicle or load, which shall in all cases aforesaid be visible not less than two hundred feet in the direction toward which the vehicle is proceeding or facing; provided, that an automobile need display no light when parked within the limits of a way in a space in which unlighted parking is permitted by the rules or regulations of the board or officer having control of such way. Every motor vehicle and trailer so operated shall be equipped with two rear lights mounted one at each side of the rear of the vehicle so as to show two red lights from behind and a white light so arranged as to illuminate and not obscure the rear number plate and shall be equipped with two stop lights mounted and displayed in a like manner of a type complying with minimum standards for construction and performance as the registrar may prescribe; provided, however, that a two-wheeled motorcycle, an antique motor car and a farm tractor need be equipped with only one such rear red light and one suitable stop light in addition to the number plate illuminator; and provided, further, that a trailer having a gross weight of three thousand pounds or less which does not obscure the required lights of the towing vehicle need be equipped with only one such rear red light and one white light so arranged as to illuminate and not obscure the rear number plate. No motor vehicle so operated shall mount or display a flashing, rotating or oscillating light in any direction except pursuant to section seven E of this chapter; provided, however, that this shall not apply to the use of rear directional signals nor to the proper use of vehicle hazard warning signals as provided for by this section. In no event, however, shall the registrar prohibit any commercial auto parts dealer, motor vehicle repair shop or station from selling, offering for sale or installing quartz-halogen headlamps which receive a certificate of approval from the American Association of Motor Vehicles Administrators or which meet the standards of the Canadian Standard Association (CSA) nor shall any provision of this section prohibit any person from using, purchasing or installing a quartz-halogen headlamp as herein described. Every motor vehicle or trailer so operated which carries a load or object extending four feet or more beyond the cab or body of such vehicle shall display at the extreme rear end of such load or object a red light plainly visible from a distance of at least five hundred feet to the sides and rear, and shall display in place thereof a red flag or cloth not less than twelve inches square during the period when motor vehicles are not required to display lights. Every commercial motor vehicle or trailer weighing, with its load, more than twelve thousand pounds, shall, in addition to such rear light, be equipped with a red reflector of a type complying with such minimum standards for construction and performance as the registrar may prescribe, so placed at the rear of such vehicle as to reflect rays of light thrown upon such reflector from behind. No headlamp or rear lamp shall be used on any motor vehicle so operated unless such headlamp or rear lamp is of a type complying with such minimum standards for construction and performance as the registrar may prescribe. Every motor vehicle shall be equipped with at least one mirror so placed and adjusted as to afford the operator a clear, reflected view of the highway to the rear and left side of the vehicle. Every motor vehicle or trailer, excepting passenger motor vehicles, operated in or upon any way shall be equipped with suitable guards which will effectively reduce the spray or splash to the rear of mud, water or slush caused by the rear wheels thereof. Every passenger motor vehicle which is equipped with tires which extend beyond the fenders or body of such vehicle and which is operated in or upon any way shall be equipped with flaps or suitable guards to reduce such spray or splash to the rear and sides. Every motor vehicle registered in the commonwealth which is privately owned and operated and designed for the carriage of passengers and which is used primarily for pleasure or for pleasure and business, including every such vehicle furnished for hire by a rental car agency but excluding every such vehicle used for public or commercial purposes, shall be equipped with two seat safety belts for the use of occupants of the front seats. No safety belt installed in a motor vehicle in accordance with the provisions of this section or in accordance with the provisions of federal law or the rules or regulations issued by the United States Department of Transportation, shall be removed from said motor vehicle except for the purpose of repairs. Every motor vehicle registered in the commonwealth shall be equipped with a device to permit the front and rear directional signals to flash simultaneously, said device to be operated only when the vehicle is disabled or stopped in the event of emergency on or at the side of any way. Every person operating a motorcycle or riding as a passenger on a motorcycle or in a sidecar attached to a motorcycle shall wear protective head gear conforming with such minimum standards of construction and performance as the registrar may prescribe, and no person operating a motorcycle shall permit any other person to ride as a passenger on such motorcycle or in a sidecar attached to such motorcycle unless such passenger is wearing such protective head gear, except that no protective head gear shall be required if the motorcyclist is participating in a properly permitted public parade and is 18 years of age or older. If a motorcycle is not equipped with a windshield or screen, the operator of such motorcycle shall wear eye glasses, goggles or a protective face shield when operating such vehicle. Every motor vehicle truck with dump bodies shall be equipped with an adequate audible warning system to alert the operator when the dump body is in an upright and elevated position. No person operating a motorcycle shall permit any person to ride as a passenger, unless such motorcycle is designed to carry more than one person; and no person operating a motorcycle shall permit a passenger to ride in front of said operator.
Every commercial motor vehicle, or trailer weighing, with its load, more than twelve thousand pounds, and used to deliver gasoline or other flammable material, shall be equipped with an audible warning system when the vehicle's transmission is in reverse. For the purpose of this paragraph, the term commercial motor vehicle or trailer shall mean a bulk tank carrier delivering gasoline or other flammable material.
Every trailer, except a semi-trailer, shall, in addition to a regular hitch, be fastened by safety chains to prevent it from breaking away from the towing vehicle. Such chains shall comply with such minimum standards for construction and performance as the registrar may prescribe.
Notwithstanding the preceding provisions of this section, any commercial motor vehicle, semi-trailer or trailer, used in interstate commerce, which shall conform as to its equipment with the regulations established from time to time by the bureau of motor carrier safety of the United States department of transportation, shall be deemed to conform to the requirements of this section.
A motor vehicle, trailer, semi-trailer or semi-trailer unit classified as a class 3 or above by the Federal Highway Administration, with a gross vehicle weight rating of 10,001 pounds or more, that is leased or purchased by the commonwealth on or after January 1, 2023, shall be equipped with a lateral protective device, convex mirrors, cross-over mirrors and backup cameras. This paragraph shall not apply to an ambulance, firefighting apparatus, low-speed vehicle, agricultural tractor or any other class or type of vehicle as determined by the registrar. The registrar shall adopt regulations establishing standards, consistent with the United States Department of Transportation John A. Volpe National Transportation Systems Center's side guard standard DOT-VNTSC-OSTR-16-05, and specifications for the size, design and mounting of lateral protective devices, convex mirrors and cross-over mirrors. The registrar may provide alternative means of compliance with the convex mirror, cross-over mirror and lateral protective device requirements.
The registrar shall prohibit: (i) visual obstructions due to aftermarket modifications and accessories that reduce the ability of the vehicle operator to directly see vulnerable users in the vicinity of the vehicle, including, but not limited to, bug deflectors and chrome visors; and (ii) aftermarket modifications and accessories that increase fatality and serious injury risk to vulnerable users in a collision with the vehicle, including, but not limited to, bull bars. The registrar shall promulgate regulations enforcing this paragraph.
No person shall sell, offer for sale or install on, or in, any motor vehicle or trailer, any component, device or substance, other than quartz-halogen lights, which does not comply with the federal motor vehicle safety standard, if any, established for such component, device or substance. Nothing in this act shall prevent the registrar from prescribing minimum standards for any component, device, or substance for which no federal motor vehicle safety standard is or has been established and no person shall sell, offer for sale or install on, or in, any motor vehicle or trailer, any such component, device or substance which does not comply with the said standards so prescribed.
Any tractor or other self propelled vehicle used exclusively for agricultural or farming purposes, excepting automobiles and trucks, the use of which is declared by the owner or person in control thereof to be restricted to the period from a half hour before sunrise to a half hour after sunset, and which is operated in or upon any way during said period shall be equipped with one stop light or a flashing red light to the rear and with brakes as manufactured, including a stationary brake with ratchet and pawl. Upon declaration by the owner or person in control of such vehicle that the use of such vehicle is to be so restricted, the person making the periodic inspection of motor vehicles and trailers, as provided under section seven A, may, notwithstanding the failure of such restricted tractor or other vehicle to have the necessary lights and other equipment required by the first paragraph of this section, issue a windshield sticker, so called, if the stop light or such flashing light and brakes are in good order. Any windshield sticker so issued shall state thereon that such vehicle is to be used upon the ways of the commonwealth only during the period from a half hour before sunrise to a half hour after sunset.
The registrar shall adopt standards and specifications for size, design, mounting, creation and use of a distinctive slow moving vehicle emblem. Every horse-drawn vehicle and every other vehicle designed to operate at twenty-five miles an hour or less, every implement of husbandry, every farm tractor, each piece of special mobile equipment and other machinery, including all road construction and maintenance machinery and every low-speed motor vehicle, traveling on a public way during day or night shall display on the rear of the vehicle such emblem. The use of such emblem shall be in addition to any lighting devices, flags or other equipment required by law. Use of such emblem as a clearance marker or on wide machinery or on stationary objects on the highways is prohibited.
Mass. Gen. Laws ch. 90, § 7