Mass. Gen. Laws ch. 153 § 1
If personal injury is caused to an employee, who, at the time of the injury, is in the exercise of due care by reason of
First, A defect in the condition of the ways, works or machinery connected with or used in the business of the employer, which arose from, or had not been discovered or remedied in consequence of, the negligence of the employer or of a person in his service who had been intrusted by him with the duty of seeing that the ways, works or machinery were in proper condition; or
Second, The negligence of a person in the service of the employer who was intrusted with and was exercising superintendence and whose sole or principal duty was that of superintendence, or, in the absence of such superintendent, of a person acting as superintendent with the authority or consent of such employer; or
Third, The negligence of a person in the service of the employer who was in charge or control of a signal, switch, locomotive engine, elevated train or train upon a railroad or elevated railway;
The employee, or his legal representatives, shall, subject to the eight following sections, have the same rights to compensation and of action against the employer as if he had not been an employee, nor in the service, nor engaged in the work, of the employer.
A car in use by or in possession of a railroad corporation, or an elevated car in use by or in possession of an elevated railway corporation, shall be considered as a part of the ways, works or machinery of the corporation which uses or has it in possession, within the meaning of clause first, whether owned by such corporation or by some other company or person. One or more cars which are in motion, whether attached to an engine or not, shall constitute a train within the meaning of clause third, and whoever, as a part of his duty for the time being, physically controls or directs the movements of a signal, switch, locomotive engine, elevated train or train shall be deemed to be a person in charge or control of a signal, switch, locomotive engine, elevated train or train within the meaning of said clause.
This section shall not apply to injuries caused to farm laborers by fellow employees.
Mass. Gen. Laws ch. 153, § 1