No person in charge of any train of cars, part of a train, car or locomotive shall permit the same to remain stationary upon any drawbridge, or upon any device or appliance controlling or affecting the opening or closing of any such bridge. No such train of cars, part of a train, car or locomotive shall, while crossing such bridge, or passing over or upon any such device or appliance aforesaid, be permitted to come to a stop unless necessary. Whenever in such case any such train of cars or part of a train, car or locomotive for any reason cannot continue in a forward direction across and off such bridge, device or appliance, such train of cars, part of a train, car or locomotive shall be immediately backed off of such bridge, device or appliance; and provided further, that after the proper signals for the opening of any such bridge have been given, no more than one (1) train of cars, part of a train, car or locomotive going in the same direction shall be passed over any such bridge, device or appliance, until such bridge, device or appliance has been moved and returned to its position.