Mass. Gen. Laws ch. 160, § 154: Brakes and brakemen

Section 154. Every railroad corporation shall cause a sufficient brake to be attached to every car used upon its railroad for the transportation of passengers, and to every car used for the transportation of freight, except four-wheel cars used only for freight; and shall cause at least one brakeman for every two cars in a passenger train to be stationed thereon, and one brakeman for the last car of every freight train to be stationed thereon. A corporation which violates this section shall forfeit not more than one hundred dollars.