Mass. Gen. Laws ch. 85 § 14B
Whenever any commercial vehicle having a gross weight in excess of five thousand pounds other than a motor bus or taxicab, or any automobile service truck, so called, becomes disabled or stops to load or unload any motorized equipment from such vehicle or from a trailer upon the traveled portion of any street or highway the operator of such vehicle shall, during the time when lights are required to be displayed on motor vehicles, place three flares on the traveled part of the way in the following positions: one flare in the center of the traffic lane in which such disabled vehicle remains and distant approximately one hundred feet from such vehicle in the direction of traffic approaching in that lane; one flare not less than one hundred feet from such vehicle in the opposite direction in said lane; and one flare at the traffic side of such vehicle, not nearer than ten feet from the front or rear of such vehicle; provided, that if such vehicle is disabled or stopped to load or unload any motorized equipment from such vehicle or from a trailer upon the traveled portion of any street or highway within three hundred feet of a curve, crest of a hill, or other place where the view of such vehicle is obstructed, the flare in that direction shall be so placed as to afford ample warning to other persons using such way, and in no case less than one hundred feet, nor more than three hundred feet, from the disabled vehicle. The word "flare" as used in this section shall mean either a lighted pot torch, a lighted red electric lamp, or a warning device meeting the requirements of Federal Motor Vehicle Safety Standard No. 125.
Every motor vehicle to which this section applies, when operated on any street or highway, shall carry at all times not less than three flares in a position where they are easily accessible to any person desiring to use the same and to any officer or official authorized to inspect said vehicle.
Violation of any provision of this section shall be punished by a fine of not more than fifty dollars and, in addition, the registrar of motor vehicles may, in the case of a motor vehicle not equipped as provided by this section, suspend for not more than fifteen days the certificate of registration of such vehicle. This section shall not apply to street railway cars and trackless trolley vehicles.
Mass. Gen. Laws ch. 85, § 14B