Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 159, § 17

All charges made, demanded or received by any common carrier for any service rendered or performed, or to be rendered or performed by it or in connection therewith in the conduct of its common carrier business, or made, demanded or received by any two or more common carriers joining in rendering or performing any service shall be just and reasonable, and every such common carrier and any two or more such common carriers joining in rendering or performing any service shall be entitled to make, demand and receive just and reasonable charges for any such service, and every unjust or unreasonable charge is hereby prohibited and declared unlawful;  but charges heretofore established and set out in any schedule filed as provided in sections nineteen and nineteen A shall be deemed prima facie lawful until changed or modified by the department under the powers conferred upon it by this chapter, but this provision shall not give to such rates any greater weight as evidence of the reasonableness of other rates than they would otherwise have.