Mass. Gen. Laws ch. 161, § 130: Construction of overpasses and underpasses

Section 130. A company, which has acquired land for such purpose, may construct its railway over or under a railroad, in the manner agreed upon by the companies, or, if they do not agree, in the manner prescribed by the department; but no overhead structure shall be built at a height of less than eighteen feet above the railroad track without the written consent of the department.