Signal box diagram colours

Colin1501 · 2 Oct 2019

From looking at numerous pictures of signal box diagrams, I am aware that the lines represented appear in a variety of colours. Presumably there are some conventions covering the colours used, eg, specific colours for main lines, sidings, loops etc. Can anyone tell me what these are/were? Did they vary between BR regions, pre-nationalisation companies, etc?

Grateful for any information.

RailUK Forums

Freightmaster · 2 Oct 2019

Here is an example of what the OP is refering to:

https://www.flickr.com/photos/43709405@N07/40305624151

The coloured sections are individual track circuits, but I'm not sure
why some are red, some green, some brown, etc...

MARK

Belperpete · 2 Oct 2019

As I recall, on most regions, track-circuits are coloured alternately dark-blue and yellow on the Up line, green and brown on the Down, with orange available if needed. Un-track-circuited lines are black. This applies to all types of line, loop, siding, etc. This convention is followed on both signalbox diagrams and panels.

The Western were different (of course), and didn't colour their diagrams or panels to denote track-circuits. I seem to recall light-blue and brown being used to denote different types of line. Unfortunately I can't currently access my notes, and can't remember more.

splashoutradio · 2 Oct 2019

One way I have had it described: the up lines are in the colours of the sky (blue and yellow), the down lines are in the colours of the ground (Brown and green). Red was used for the track circuit for the outermost home signal (i.e. the first stop signal a train comes to) but this has mostly been retired. Where needed other colours can be used, but not sure how those are decided - Edgeley Jn No.2 box has a track circuit in Pink!

alxndr · 3 Oct 2019

splashoutradio said:
One way I have had it described: the up lines are in the colours of the sky (blue and yellow), the down lines are in the colours of the ground (Brown and green). Red was used for the track circuit for the outermost home signal (i.e. the first stop signal a train comes to) but this has mostly been retired. Where needed other colours can be used, but not sure how those are decided - Edgeley Jn No.2 box has a track circuit in Pink!

Interestingly they use a similar colour scheme for TPWS modules and that's also how I remember them (Yellow and Blue, the sky colours, for Over Speed modules as the sky is over your head, Train Stop are Green and Brown).

godfreycomplex · 3 Oct 2019

splashoutradio said:
One way I have had it described: the up lines are in the colours of the sky (blue and yellow), the down lines are in the colours of the ground (Brown and green). Red was used for the track circuit for the outermost home signal (i.e. the first stop signal a train comes to) but this has mostly been retired. Where needed other colours can be used, but not sure how those are decided - Edgeley Jn No.2 box has a track circuit in Pink!

Feltham has several in pink as well. Refers to a t/c that has relevance to routes in both directions (overlaps, for instance), although Edgeley No. 2 is AB at one end I believe so not sure what that one’s for as I’ve not been up there

Tomnick · 3 Oct 2019

Wherever I’ve come across pink or any other unusual colour, it’s had no particular significance other than appearing to prevent the ‘standard’ colours clashing on adjoining track circuits or adjacent lines in complex pointwork.

I’ve found a relevant snippet from a now superseded standard which sort of supports that:

# The colours shown shall be used whenever track circuit sections require to be defined by the use of different colours. Where this is the case, green and brown (or orange) shall be used for one line (usually down direction) and blue and yellow shall be used for the adjacent line (usually up line), repeating as necessary for additional lines. One additional non–conflicting colour (Light Violet, BS 381C shade 797 is recommended) may be used only in exceptional circumstances during alterations where the use of an additional colour would reduce the number of required consequential alterations.

https://catalogues.rssb.co.uk/rgs/standards/GKRT0005 Iss 2.pdf

John Webb · 3 Oct 2019

Here is a track diagram from 1970:

From the preserved St Albans South signal box. The berth track circuits approaching the home signals 2, 8, 36/34/25 and 43 are red, T6 is in red to avoid a clash at crossover 4, I assume. (The two dots visible on many of the TCs are where the lampholders were to be fitted when the diagram was reconstructed.)

MarkyT · 3 Oct 2019

Note the blue/yellow, brown/green scheme is also standard for panels as well. Example at Three Bridges:

MarkyT · 3 Oct 2019

Belperpete said:
The Western were different (of course), and didn't colour their diagrams or panels to denote track-circuits. I seem to recall light-blue and brown being used to denote different types of line. Unfortunately I can't currently access my notes, and can't remember more.

Solid fill black is track circuited on WR SBDs and panels, separated by white joint boundaries. Outline only for non track circuited track filled with base background color on panels and tinted blue or other pastel colours to denote non track-circuited passenger, freight, sidings etc on SBDs.

Belperpete · 3 Oct 2019

John Webb said:
From the preserved St Albans South signal box.

Whoever drew that St Albans diagram seems to have driven a coach and horses through the blue/yellow for up and green/brown for down convention!

I can't recall ever seeing track-circuits coloured red on any Southern Region diagrams, and can't recall anything about it in the BR standard. Was this an LM-only thing, or did any other regions do it?

John Webb · 3 Oct 2019

Belperpete said:
Whoever drew that St Albans diagram seems to have driven a coach and horses through the blue/yellow for up and green/brown for down convention!

I can't recall ever seeing track-circuits coloured red on any Southern Region diagrams, and can't recall anything about it in the BR standard. Was this an LM-only thing, or did any other regions do it?

We were BR (LMR) at the time. Diagram dates from 1970 when the North box was closed and the South box reconfigured to cover the whole station area following closure of the goods yard circa 1967.

Belperpete · 3 Oct 2019

MarkyT said:
Solid fill black is track circuited on WR SBDs and panels, separated by white joint boundaries. Outline only for non track circuited track filled with base background color on panels and tinted blue or other pastel colours to denote non track-circuited passenger, freight, sidings etc on SBDs.

I have just realised that my notes aren't quite as inaccessible as I thought. My notes on colouring box diagrams from when I worked in the Reading DO say that passenger lines should be grey, and sidings, freight lines, etc (inc shunting crossovers) should be blue.

Signalboxes red, ground frames green. Disc signals to have red bar - green bar when GF-controlled. Can't recall ever seeing a green-bar disc on a diagram (obviously the signal itself wouldn't have a green bar!).

LAX54 · 3 Oct 2019

MarkyT said:
Note the blue/yellow, brown/green scheme is also standard for panels as well. Example at Three Bridges:View attachment 69006

As they are here (Colchester) Blue / Yellow Up Line, Brown / Green Down Line, however we have two purple tracks (both on Up and Down), these were added when they were going to split the tracks in the platforms at Ipswich, and would be yellow/yellow or blue/blue, inserting the purple overcame this.

MarkyT · 3 Oct 2019

Belperpete said:
...Can't recall ever seeing a green-bar disc on a diagram (obviously the signal itself wouldn't have a green bar!).

I also cannot recall seeing a green bar on a disc symbol. In my experience any ground frame operated points and signals would be shown normally, and marked with a symbol referencing the particular GF. Colouring of diagram features, just like levers and even aspect colours, evolved slowly over the years though, so it's highly plausible they were officially supposed to be green at some time in history.

Dunfanaghy Rd · 3 Oct 2019

Here is a portion of Chichester Panel that I took some years ago.

The use of violet allowed for splicing in an extra TC. (I knew this pic would come in handy one day!)
Pat

Signal box diagram colours

Colin1501

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Freightmaster

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