Mass. Gen. Laws ch. 159, § 3: Limitations upon liability imposed by carrier

Section 3. No common carrier of passengers shall, by rule, regulation, sign or otherwise, require passengers whom it suffers to enter, or leave by, a door of its car or train, to do so at their own risk; and no such passenger shall be prevented from recovering compensation in damages for any injury by reason of any such rule, regulation, sign or requirement.