Mass. Gen. Laws ch. 161 § 103
A day's work for all conductors, guards, drivers, motormen, brakemen, dispatchers and gatemen employed by or on behalf of a street railway or elevated railway company shall not exceed nine hours, and shall be so arranged by the employer that it shall be performed within eleven consecutive hours. No officer or agent of any such company shall require from said employees more than nine hours' work for a day's labor. Threat of loss of employment or threat to obstruct or prevent the obtaining of employment by the employees, or threat to refrain from employing any employee in the future shall be considered "requiring", within the meaning of this section. But this section shall not prevent an employee of the character mentioned herein, if he so desires, from working more hours than those prescribed herein for extra compensation. A company violating any provision of this section shall forfeit not less than one hundred nor more than five hundred dollars.
Mass. Gen. Laws ch. 161, § 103