Wasn`t it the guards job to change the lenses in the side lamps, depending on which line the train was running? A train, such as that in the photo,
would have three red lights, two side and one tail. If the train were signalled onto the slow line or into a goods loop, then the guard would remove
the red shade from the lamp adjacent to the fast or main line. If the side lamps were carreied at the front of the van, they may not be fully visible
to a train approaching from the rear, such as on right hand curves?