No member of a train crew, yard crew, or engine crew of a railroad shall be held personally responsible or found guilty of violating any state laws or any municipal ordinances regulating or intended to regulate the occupying or blocking of any street, road, or highway crossing-at-grade by trains or passenger or freight cars upon reasonable proof that the occupying or blocking of the street, road, or highway crossing-at-grade was necessary to comply with orders or instructions either written or oral of his or her employer or its officers or supervisory officials. This section shall not relieve the employer or railroad from any responsibility placed upon the employer or railroad by any such state laws or by such municipal ordinances. This section shall be supplemental to any other law.