What is the colour light signaling equivalent of a "Shunt Ahead" signal?

[Tallpaul69]

Hello All,

In BR(W) signaling practice when colour light signals replaced semaphores during the 60s, what replaced a "Shunt Ahead" signal?

I am thinking of a situation where it was wanted to allowing an engine on a down line to leave its train and move forward over a crossover to the up line and then when a ground signal went green reverse over the crossover.

If the loco came back over the crossover, what signal allowed it to then reverse onto its train? 

 

Did practice change through the "modern" era up to today? 

 

Many thanks

Paul  

[iands]

If colour light signals had replaced semaphore signals, either a single yellow "main aspect" or if fitted, a sub signal (two white lights at 45 degrees). The "ground signal went green" - I'm assuming the ground signal is a disc signal rather than a colour light GPL equivalent?

[DY444]

On the WR it would be either a Ground Position Light signal or a subsidiary signal attached to a running signal.

Edited October 21, 2020 by DY444

[DY444]

1 minute ago, iands said:

If colour light signals had replaced semaphore signals, either a single yellow "main aspect" or if fitted, a sub signal (two white lights at 45 degrees). The "ground signal went green" - I'm assuming the ground signal is a disc signal rather than a colour light GPL equivalent?

 

I would be very surprised indeed if any 1960s and later signalling schemes featured arrangements where a running signal could display a yellow aspect into an occupied section.   

[iands]

1 minute ago, DY444 said:

 

I would be very surprised indeed if any 1960s and later signalling schemes featured arrangements where a running signal could display a yellow aspect into an occupied section.   

I read the OP as the section ahead was not occupied, hence it could be a "yellow", but acknowledging that the section could have been occupied hence the "sub signal" statement. Apologies if my response was a bit confusing.

[Tallpaul69]

57 minutes ago, iands said:

I'm assuming the ground signal is a disc signal rather than a colour light GPL equivalent?

 

56 minutes ago, DY444 said:

On the WR it would be either a Ground Position Light signal or a subsidiary signal attached to a running signal.

 

46 minutes ago, iands said:

I read the OP as the section ahead was not occupied, hence it could be a "yellow",

OK Guys, thanks for the input.

Some clarifications:-

The section ahead is NOT occupied.

The ground signal is a colour light

Please confirm the suggestion that the signal could be a "subsidiary signal attached to a running signal" if the running signal was a starter?  What would this look like? - a ground signal but part way up the starter signal pole? - or something different?

 

Many thanks

Paul

 

[iands]

1 minute ago, Tallpaul69 said:

 

 

OK Guys, thanks for the input.

Some clarifications:-

The section ahead is NOT occupied.

The ground signal is a colour light

Please confirm the suggestion that the signal could be a "subsidiary signal attached to a running signal" if the running signal was a starter?  What would this look like? - a ground signal but part way up the starter signal pole? - or something different?

 

Many thanks

Paul

 

Usually (but not always) the sub-signal will be positioned on the same post below the main signal head. The sub-signal is to all intents and purposes a GPL with the "red" light blanked off, so only the white "pivot" light (bottom right when viewed from the front) and upper left white light will show illuminated when the sub-signal is "off". I'll see if I can find a decent photo, but someone else may be able to find one if I can't.

[DY444]

13 hours ago, Tallpaul69 said:

 

 

OK Guys, thanks for the input.

Some clarifications:-

The section ahead is NOT occupied.

The ground signal is a colour light

Please confirm the suggestion that the signal could be a "subsidiary signal attached to a running signal" if the running signal was a starter?  What would this look like? - a ground signal but part way up the starter signal pole? - or something different?

 

Many thanks

Paul

 

I'm confused now.  Your first post said:

 

"If the loco came back over the crossover, what signal allowed it to then reverse onto its train? "

 

That was the question I thought I was answering and the section is therefore occupied by the train the loco is reversing onto. 

 

The signal allowing it to reverse onto its train could be a ground position light or a running signal.  If the latter then it would not show a proceed aspect on the main signal head but would have a subsidiary signal attached which allowed a permissive move into the occupied section. 

 

A typical WR 1960s vintage signal with a sub signal would look like this:

 

https://photos.signalling.org/picture?/10739/category/1002-reading_station_west

 

Edited October 22, 2020 by DY444

[iands]

28 minutes ago, DY444 said:

 

I'm confused now.  Your first post said:

 

"If the loco came back over the crossover, what signal allowed it to then reverse onto its train? "

 

That was the question I thought I was answering and the section is therefore occupied by the train the loco is reversing onto. 

 

The signal allowing it to reverse onto its train could be a ground position light or a running signal.  If the latter then it would not show a proceed aspect on the main signal head but would have a subsidiary signal attached which allowed a permissive move into the occupied section. 

 

A typical WR 1960s vintage signal with a sub signal would look like this:

 

https://photos.signalling.org/picture?/10739/category/1002-reading_station_west

 

Good point DY444. I read the OP to mean the signal train was stood at before any Shunt move started. Rereading the OP I'm now a bit confused and take your point. 

[The Stationmaster]

17 hours ago, Tallpaul69 said:

Hello All,

In BR(W) signaling practice when colour light signals replaced semaphores during the 60s, what replaced a "Shunt Ahead" signal?

I am thinking of a situation where it was wanted to allowing an engine on a down line to leave its train and move forward over a crossover to the up line and then when a ground signal went green reverse over the crossover.

If the loco came back over the crossover, what signal allowed it to then reverse onto its train? 

 

Did practice change through the "modern" era up to today? 

 

Many thanks

Paul  

While agreeing with everything which has been said about signalling shunt ahead moves in a colour light signalled area (and don't forget that Shunt Ahead subs installed in the 1960s were pretty rare birds and by the late 1960s I doubt if any more were ever installed).  Can anybody name a place where a genuine Shunt Ahead subsidiary was actually installed (which would have to be on a colour light Section Signal on a line worked by Absolute Block)?

 

But the OP does not ask about a shunt ahead movement but a movement crossing from one line to another as I have highlighted.  So the answer is that it would be signalled using a GPL.  and that has of course been the answer in British colour light signalling practice since the 1930s with certain exceptions such as the GWR using miniature colour light signals - of various forms, or the SR using illuminated power operated ground discs and still installing them in new work until 1965/66 when it changed over to using GPLs

Edited October 22, 2020 by The Stationmaster

[The Stationmaster]

2 hours ago, DY444 said:

 

 

 

A typical WR 1960s vintage signal with a sub signal would look like this:

 

https://photos.signalling.org/picture?/10739/category/1002-reading_station_west

 

But being pedantic it didn't look like that in the 1960s because that signal has had the original numberplate replaced by one in the later standard colouring instead of the WR standard of black numerals on a white background; the telephone case is a commercial item which has replaced the original, larger, Reading works style item and is painted in a different way; the stencil indicator at the top of the post is a replacement LED indicator which was substituted for the original Reading pattern stencil indicatir; and the stencil style LED indicator alongside the sub is a much later addition as it is an RA indicator and wasn't added until the late 1980s/early '90s.

[DY444]

1 hour ago, The Stationmaster said:

But being pedantic it didn't look like that in the 1960s because that signal has had the original numberplate replaced by one in the later standard colouring instead of the WR standard of black numerals on a white background; the telephone case is a commercial item which has replaced the original, larger, Reading works style item and is painted in a different way; the stencil indicator at the top of the post is a replacement LED indicator which was substituted for the original Reading pattern stencil indicatir; and the stencil style LED indicator alongside the sub is a much later addition as it is an RA indicator and wasn't added until the late 1980s/early '90s.

 

Drat rumbled.  I couldn't in my haste immediately find a picture of an original WR pattern one which had both a sub head mounted on a front facing bracket and all original other features.   

 

However how about this (ignoring the SPT!):

 

https://photos.signalling.org/picture?/10763/category/999-new_jn

Edited October 22, 2020 by DY444

[Pandora]

A ground position signal head  with a total of 3 lights comprised of  2 whites and 1 yellow,  of which pairs of lights,  are displayed so the the signal is capable of displaying 2 aspects., 1)  shunt ahead is  1 yellow plus 1 white) or, 2)   move onto the mainline, (two whites)

 

 

One of the lights is called  the pivot light and is common to both aspects, it is the light  on the right and is a white.

 

For a shunt ahead movement the driver sees a yellow plus a white  (the white being the pivot light) .

 

When the movement is set for the mainline, the signal will show two whites, the   the driver will see the  the top white plus the  pivot light.

 

 

 

 

 

[Tallpaul69]

Good Afternoon All,

 

Apologies for creating confusion!

 

In my initial post I said:-

 

"In BR(W) signaling practice when colour light signals replaced semaphores during the 60s, what replaced a "Shunt Ahead" signal?

I am thinking of a situation where it was wanted to allowing an engine on a down line to leave its train and move forward over a crossover to the up line and then when a ground signal went green reverse over the crossover.

If the loco came back over the crossover, what signal allowed it to then reverse onto its train? 

 

Did practice change through the "modern" era up to today? "

 

What I meant to say was:-

"In BR(W) signaling practice when colour light signals replaced semaphores during the 60s, what replaced a "Shunt Ahead" signal?

I am thinking of a situation where in semaphores a "shunt Ahead" signal on the same post as the Starter allowed an engine on a down line to leave its train and move forward in order to reverse over a crossover to the up line.

Also, if the loco then came back over the crossover, (once the correct points and ground signals were set) what signal allowed it to reverse onto its train once the points had been reset? 

Did practice change through the "modern" era up to today? "

 

I hope this is now clear?

Many thanks

Paul

 

[RailWest]

>>>"In BR(W) signaling practice .....I am thinking of a situation where in semaphores a "shunt Ahead" signal on the same post as the Starter allowed an engine on a down line to leave its train and move forward in order to reverse over a crossover to the up line...."

 

On double-track BR(WR) lines were there are such situations anyway? I would have thought that the provision of a SA arm would have occurred only if there was no Advanced Starting signal in advance of the crossover (so the Starting signal was the section signal). Not something which I can recall on ex-GWR lines, but maybe Stationmaster knows of an obscure example or two ?

[Edwin_m]

Isn't a shunt ahead only to allow the train to move far enough to shunt back over a trailing point that's before (in rear of) the signal in question?  If so then there's no real colour light equivalent.  The forward move would be a main aspect if the route was clear to the next main stop signal, the driver would know where to stop for the shunt but if they carried on to the next signal it would be inconvenient rather than dangerous.  This is unlike a semaphore shunt ahead which is presumably only needed if there's some reason the main signal can't be cleared. 

 

If there was a need to do this without clearing the main signal (because of a train or conflicting junction further along the route) then there would be a subsidiary aspect reading to a ground signal marking the limit of the shunt move, which would be cleared in a "preset" mode when the main route was set.  

[RailWest]

1 hour ago, Edwin_m said:

Isn't a shunt ahead only to allow the train to move far enough to shunt back over a trailing point that's before (in rear of) the signal in question?  If so then there's no real colour light equivalent.  The forward move would be a main aspect if the route was clear to the next main stop signal, the driver would know where to stop for the shunt but if they carried on to the next signal it would be inconvenient rather than dangerous.  This is unlike a semaphore shunt ahead which is presumably only needed if there's some reason the main signal can't be cleared. 

 

If there was a need to do this without clearing the main signal (because of a train or conflicting junction further along the route) then there would be a subsidiary aspect reading to a ground signal marking the limit of the shunt move, which would be cleared in a "preset" mode when the main route was set.  

With respect, there seems to be a lot of confusion here, apparently with the idea of a SA being used to shunt into a signal section - ie the length of line from one stop signal to another controlled by the same SB. In the semaphore era IMHO a SA was normally found below a section signal and controlled moves into a block section.

[Edwin_m]

23 minutes ago, RailWest said:

With respect, there seems to be a lot of confusion here, apparently with the idea of a SA being used to shunt into a signal section - ie the length of line from one stop signal to another controlled by the same SB. In the semaphore era IMHO a SA was normally found below a section signal and controlled moves into a block section.

Yes I agree, I was thinking of a section signal but didn't say so, and my comment about next main signal applied to colour lights.  Apologies if this wasn't clear. 

 

As my experience is in more recent types of signalling, I don't recall if shunt-ahead was allowed "behind" a train in the section, or whether it needed some sort of acceptance from the box at the other end of that section.  

Edited October 22, 2020 by Edwin_m

[Tallpaul69]

Agreed,

In the example I quoted the semaphore signal was a starter with a "shunt ahead" (or calling on?) Signal below it. Forward of this signal post was another section controlled by the next signal box. There was no advanced starter.

 

I am trying to sort this out for a layout I am planning. To avoid using curved points the crossover referred to will be behind the signal post but not so far that the locomotive can move forward to back over the crossover without passing the signal post.

 

The intention is to run this layout in c1960 and c1990 versions, hence the interest in the colour light version of the signals.

 

Hope this information allows folk to correctly answer my question?

 

Many thanks

Paul

[bécasse]

I have never come across a shunt ahead signal that wasn't mounted below the furthest advanced starting signal which controlled entry to an absolute block or single line section. While it is possible that that signal could have been a colour light signal (normally two aspect rather than three or four), colour light signals were, and still are, most commonly associated with track circuit block, and I cannot see that the concept of shunting ahead on the running line under the authority of a subsidiary signal is compatible with track circuit block and I am very doubtful as to whether an Inspecting Officer would have permitted it.

 

I do know of one place where it was done (on parallel fast and slow lines) and the signals concerned were in place for less than eight hours before they were spotted by an incredulous Inspecting Officer. He took the view that they allowed permissive working on a passenger line and insisted that they be physically removed immediately while he watched.

[RailWest]

1 hour ago, Tallpaul69 said:

Agreed,

In the example I quoted the semaphore signal was a starter with a "shunt ahead" (or calling on?) Signal below it. Forward of this signal post was another section controlled by the next signal box. There was no advanced starter.

 

I am trying to sort this out for a layout I am planning. To avoid using curved points the crossover referred to will be behind the signal post but not so far that the locomotive can move forward to back over the crossover without passing the signal post.

 

The intention is to run this layout in c1960 and c1990 versions, hence the interest in the colour light version of the signals.

 

Hope this information allows folk to correctly answer my question?

 

Many thanks

Paul

Ah, now that makes a little more sense - not the impression gained from the original posting :-)

 

So - why not just move the main signal further away from the crossover?

[Flying Pig]

2 hours ago, Tallpaul69 said:

I am trying to sort this out for a layout I am planning. To avoid using curved points the crossover referred to will be behind the signal post but not so far that the locomotive can move forward to back over the crossover without passing the signal post.

 

I think it would be helpful for you to post a diagram of the signalling layout you have in mind, so the experts can address the specifics of the situation.

[The Stationmaster]

23 hours ago, DY444 said:

 

Drat rumbled.  I couldn't in my haste immediately find a picture of an original WR pattern one which had both a sub head mounted on a front facing bracket and all original other features.   

 

However how about this (ignoring the SPT!):

 

https://photos.signalling.org/picture?/10763/category/999-new_jn

That's much better (as you say - apart from the 'phone) and it's one of the Reading signals I don't have a photo of.

 

20 hours ago, Tallpaul69 said:

Good Afternoon All,

 

Apologies for creating confusion!

 

In my initial post I said:-

 

"In BR(W) signaling practice when colour light signals replaced semaphores during the 60s, what replaced a "Shunt Ahead" signal?

I am thinking of a situation where it was wanted to allowing an engine on a down line to leave its train and move forward over a crossover to the up line and then when a ground signal went green reverse over the crossover.

If the loco came back over the crossover, what signal allowed it to then reverse onto its train? 

 

Did practice change through the "modern" era up to today? "

 

What I meant to say was:-

"In BR(W) signaling practice when colour light signals replaced semaphores during the 60s, what replaced a "Shunt Ahead" signal?

I am thinking of a situation where in semaphores a "shunt Ahead" signal on the same post as the Starter allowed an engine on a down line to leave its train and move forward in order to reverse over a crossover to the up line.

Also, if the loco then came back over the crossover, (once the correct points and ground signals were set) what signal allowed it to reverse onto its train once the points had been reset? 

Did practice change through the "modern" era up to today? "

 

I hope this is now clear?

Many thanks

Paul

 

The simple answer is that nothing replaced  a Shunt Ahead Subsidiary where colour light signalling with Track Circuit Block working is involved.  

 

The reason for that is because in normal Absolute Block qw working with semaphore (or even colour light) signals a Shunt Ahead Subsidiary was placed below the Section Signal (which is the signal that controls the entrance to the section in advance) in order to signal a shunting movement into the block section for as far as it needed to go - and only that far - in order to carry out shunting work..  This requires the co-operative action of the Signalmen in the 'boxes at each end of the block section.   Shunting into the forward section was only allowed where authoised and it was not authorised at, probably, the majority of signal boxes

 

This situation cannot apply with Track Circuit Block working because there is no need for co-operative action between adjacent signal boxes to authorise a movement into the signal sections between their 'boxes.  Additionally there will probably be a number of signal sections in advance of the signal which needs to be passed for the sort of move you have in mind so the simple answer is to clear the main aspect when the line is clear to the next signal (and its overlap track circuit).  In some cases a position light subsidiary might be provided to permit a shunting movement to be made in order to get beyond a GPL to take the move back to another line in very busy locations but that would be very unusual.  And I think almost invariably on teh WR such subs read towards another line and not into the signal section immediately in advance.  But it is a shunting signal (referred to as a Draw Ahead signal in some years) and not a Shunt Ahead Subsidiary.

 

What you could find frequently on the WR MAS schemes was a subsidiary working in an equivalent manner to a semaphore Calling On Subsidiary but off hand I can't think of one anywhere which allowed a shunt along the running route for purely shunting purposes.

 

16 hours ago, Edwin_m said:

Yes I agree, I was thinking of a section signal but didn't say so, and my comment about next main signal applied to colour lights.  Apologies if this wasn't clear. 

 

As my experience is in more recent types of signalling, I don't recall if shunt-ahead was allowed "behind" a train in the section, or whether it needed some sort of acceptance from the box at the other end of that section.  

Simple answer is 'yes' and 'no'.  The Regulation allowed a shunt into the forward section if the block indicator was at 'Train on Line' but other Regulations effectively prevented two movements  to take place simultaneously in the same direction in an Absolute Block section.  So the block being at ToL  could be because the Clearing Point at the next 'box in advance was fouled for some reason (which might be a train which had arrived and was within the protection of signals or a Block Back had been put on).   There was nothing in the Regulations, except in very short section, to prevent a shunt being made into the advance section if there was a Block Back already in operation in the section (and vice versa).  So in that respect it was broadly equivalent to the single line Block Regulations which allowed shunts to be made simultaneously into both  ends of a single line section.

[DY444]

22 minutes ago, The Stationmaster said:

That's much better (as you say - apart from the 'phone) and it's one of the Reading signals I don't have a photo of.

 

The simple answer is that nothing replaced  a Shunt Ahead Subsidiary where colour light signalling with Track Circuit Block working is involved.  

 

The reason for that is because in normal Absolute Block qw working with semaphore (or even colour light) signals a Shunt Ahead Subsidiary was placed below the Section Signal (which is the signal that controls the entrance to the section in advance) in order to signal a shunting movement into the block section for as far as it needed to go - and only that far - in order to carry out shunting work..  This requires the co-operative action of the Signalmen in the 'boxes at each end of the block section.   Shunting into the forward section was only allowed where authoised and it was not authorised at, probably, the majority of signal boxes

 

This situation cannot apply with Track Circuit Block working because there is no need for co-operative action between adjacent signal boxes to authorise a movement into the signal sections between their 'boxes.  Additionally there will probably be a number of signal sections in advance of the signal which needs to be passed for the sort of move you have in mind so the simple answer is to clear the main aspect when the line is clear to the next signal (and its overlap track circuit).  In some cases a position light subsidiary might be provided to permit a shunting movement to be made in order to get beyond a GPL to take the move back to another line in very busy locations but that would be very unusual.  And I think almost invariably on teh WR such subs read towards another line and not into the signal section immediately in advance.  But it is a shunting signal (referred to as a Draw Ahead signal in some years) and not a Shunt Ahead Subsidiary.

 

What you could find frequently on the WR MAS schemes was a subsidiary working in an equivalent manner to a semaphore Calling On Subsidiary but off hand I can't think of one anywhere which allowed a shunt along the running route for purely shunting purposes.

 

Simple answer is 'yes' and 'no'.  The Regulation allowed a shunt into the forward section if the block indicator was at 'Train on Line' but other Regulations effectively prevented two movements  to take place simultaneously in the same direction in an Absolute Block section.  So the block being at ToL  could be because the Clearing Point at the next 'box in advance was fouled for some reason (which might be a train which had arrived and was within the protection of signals or a Block Back had been put on).   There was nothing in the Regulations, except in very short section, to prevent a shunt being made into the advance section if there was a Block Back already in operation in the section (and vice versa).  So in that respect it was broadly equivalent to the single line Block Regulations which allowed shunts to be made simultaneously into both  ends of a single line section.

 

I can't say how widespread it was across the WR but there were certainly some routes on Bristol PSB which could be cleared as either main or sub. 

[Pandora]

21 hours ago, Edwin_m said:

Isn't a shunt ahead only to allow the train to move far enough to shunt back over a trailing point that's before (in rear of) the signal in question?  If so then there's no real colour light equivalent.  The forward move would be a main aspect if the route was clear to the next main stop signal, the driver would know where to stop for the shunt but if they carried on to the next signal it would be inconvenient rather than dangerous.  This is unlike a semaphore shunt ahead which is presumably only needed if there's some reason the main signal can't be cleared. 

 

If there was a need to do this without clearing the main signal (because of a train or conflicting junction further along the route) then there would be a subsidiary aspect reading to a ground signal marking the limit of the shunt move, which would be cleared in a "preset" mode when the main route was set.  

"ground signal marking the limit of the shunt move, which would be cleared in a "preset" mode when the main route was set"  Drivers call such signals " A Running Dummy" showing two whites to trains travelling in the "Right Direction"

When the shunt move is leaving one line and entering the opposite line therefore temporarily travelling  "Wrong Direction" , the driver should see a limit of shunt signal, which could be a Stop Board or a ground position signal showing 2 reds and the signal plate may written simply as LOS

Edited October 23, 2020 by Pandora