Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 160, § 97

A railroad laid out across a public way shall be so constructed as not to obstruct the same; and, unless the county commissioners and the department authorize a crossing at the same level as provided in section one hundred and two, it shall be constructed so as to pass either over or under the way, as prescribed in the following section, and conformably to any decree which may be made by the county commissioners under section one hundred.