I’m hoping someone will help me with the best way to signal a section of my layout. I think i've got a basic understanding of signalling on the mainline, but maybe not so much around junctions. I’ve included in a drawing of the layout and what i plan to have in terms of mainline signalling (correct me if it’s wrong please), but i'm not sure about subsidiary signalling which is where i’m really looking for help. Here’s a quick description of layout and my thinking.
The layout is based about 1987 (give or take a year or 2), and is based on an extension of the WCML north of Glasgow. Carstairs is an inspiration but instead of trains splitting and half continuing with original loco, and the other half leaving behind a diesel, i plan to run trains in from GLA on the left, and then the train leaves to KK with a new loco pulling it.
I plan to use 4 Aspect signals. All 4 lines through the station are bi-directional so the signals on each of the approaches to the station have theatre route indicators (black boxes on drawing), although the 2 to the left will be off scene. The 4 signals at the left end of the station have feather indicators to show which route the train will take on departure. The mainlines leading to INV are in the process of being electrified so any trains continuing that way have to change to diesel haulage. (Platforms are outlined in pink – ie 3 platforms and 1 loop).
The blue sidings are the loco stable, green sidings are for engineers, timber loading. I presume all these sidings would probably be controlled by a ground frame? What sort of signal would allow trains to leave the sidings? Is a GPL enough? I plan light engines moving from the loco stable onto trains reversing direction at the station, but also engineer / timber trains would depart onto mainlines.
What sort of signal would be used to leave the headshunt onto the loop/ sidings? Is a GPL enough?
Would the 4 aspect on the loop need a subsidiary signal (as indicated) to allow access to the headshunt?
Thanks for any advice comments received.