No member of a train crew, yard crew or engine crew of a railroad, which is a common carrier, shall be held personally responsible or found guilty of violating any law of this state or any municipal ordinance 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 said street, road or highway crossing-at-grade was necessary to comply with the orders or instructions either written or oral of his employer or its officers or supervisory officials; provided, that the provisions of this section shall not relieve the employer or railroad from any responsibility placed upon said employee or railroad by any such state laws or by such municipal ordinances; provided further, that nothing contained herein shall affect any civil tortious responsibility of the agent, servants, employees and the railroad itself.