This photograph was taken from the footbridge at Grosmont station, which lies at the north end of the preserved North Yorkshire Moors Railway. We are looking south, which is the "Up" direction (that is, towards London). Although it might look as if double track leads away from Grosmont and through the tunnel, there is in fact only a single main line, the right hand side track. The track to the left leads to the depot and then terminates.

I took this photograph because of the signals. The left hand post controls trains departing from Platforms 4 (far left) and 3 (near left). Trains departing Platform 4 are controlled by the two smaller posts (or "dollies") to the left of the main post, and trains departing Platform 3 by the two dollies to the right of the main post. The right hand post controls trains departing platform 2, on the right of the picture. (Platform 1 is off the screen to the right of this picture and is still part of the national rail network, being served by trains on the Middlesborough-Whitby route).

For each pair of dollies, the larger signal arm on the right tells the driver that access to the main line is clear. The smaller arm on the left tells the driver that access to the left hand line, leading to the depot, is clear. At some time the track layout has been altered so that the left hand line is no longer directly accessible from Platform 2, and therefore the smaller branch signal has been crossed out.

When a train leaves Grosmont, the main line will not be signalled as clear until it reaches the next signal box at Goathland, several miles along the line. However, once it has passed the "limit of shunt", which typically lies a few hundred yards along the main line and within sight of the signal box, it is safe for another train carrying out shunting movements to move along the line as far as the limit of shunt. The small arm below each main arm is a "calling on" or "draw down" signal, which allows shunting movements using the main line.