I am thinking of the case where a loco might move forward beyond a Starter and fouling distance (but with an 'on' Advanced Starter still ahead) and later need to reverse on the same line to behind the Starter, essentially to where it started. The loco would need to be held beyond the fouling distance before being permitted to reverse, suggesting the need for a backing signal but I have yet to find any evidence.
Any information gratefully received.
Despite 'Working In Wrong Direction' being authorised between all of the Chester boxes no discs/signals were provided for these moves, reliance being placed on Hand Signals, even from the 'Big' boxes.
At Aylesbury (terminus station) there was no engine release so the train was backed out of the platform for running round. A standard ground signal was provided for the driver in order to do that, as from his position he couldn't see anything else.
Sorry to go off at a tangent, but at Aylesbury there was just one running line and when setting back from the platform you could only to straight down that or left into the goods reception road, which was rarely used for passenger trains. The points into the passenger run round loop were trailing when you leave the platform. I always assumed the co-acting signals gave permission to run as far as the next home signal to stop and run round. But isn't that what the starting signal did too? In short, what was the difference between the two in operation?
- Aylesbury overhead view.jpg (124.48 KiB) Viewed 105 times
Co-acting = signals which work together for sighting purposes e.g. an arm on a tall post for sighting over a physical obstruction, co-acting with another arm lower down for closer viewing. (still sometimes used with colour light signal heads such as at Birmingham New Street near the tunnels, a ground-mounted signal head co-acting with an elevated one).
Subsidiary Signal - distinguished from the 'Main' arm by being smaller, could be used as a 'Shunt Ahead', 'Call On' (towards an occupied line) or 'Warning' (that the line was only clear to the next signal). Subsidiary signals give permission to pass the 'Main Arm', mounted above, at Danger.
I think that's enough for now, as it can get complicated with various arrangements used in different places/time periods. For example, Rule Book clauses covered situations where 'Sub' signals were not provided.
Please feel free to ask any further questions.
Other material I have found confirms that shorter semaphores were occasionally used, for the purposes described in this thread. It looks like they could also be deployed to control reversing too. By the sound of it, this may be rare!