Mass. Gen. Laws ch. 160 § 136
The department shall make general regulations for all such crossings or special regulations for such particular crossings as it may designate, and in such detail as it may consider expedient; and the supreme judicial court may issue any processes necessary to secure the enforcement of such regulations, or, upon the petition of the department, may enjoin the running of trains on a railroad upon which any regulation relative to such crossing is not exactly observed. The approval of the department shall be required for a system of signals to be established and maintained in concert by corporations operating railroads which cross each other; but no such regulation or system of signals shall exempt a railroad upon or across which passenger trains are run from the requirements of the preceding section, unless a system of interlocking or automatic signals, approved in writing by the department, is adopted by both corporations.
Mass. Gen. Laws ch. 160, § 136