That all companies, corporations, lessees, owners, operators or receivers of any railroad or railway company operating a railroad or railway in whole or in part in this state, are hereby required to equip, maintain and use upon every locomotive being operated in road service in this state in the nighttime an electric headlight of fifteen hundred candle power brilliancy, measured with the aid of a reflector, and classification signals not less than six candle power; provided, that nothing in this law shall be so construed as to prevent a locomotive engine whose headlight has become defective while on the road from proceeding to the most convenient terminal or division point where the necessary facilities exist for remedying such defect, but nothing in this law shall relieve any such company, corporation, lessee, owner, operator or receiver of any railroad or railway company of any liability for injury or damage to persons or property, or for the death of any person, caused by proceeding with an engine having such defective headlight; and provided further, that the provisions of this law shall not apply to independent lines of railroad less than seventy-five miles in length; and provided further, that the provisions of this law shall not apply during the first ninety days of a strike of the particular employees whose duties are to repair and maintain electric headlights.