Signalling for Braeintra - Interlocking

[bécasse]

Interesting, but perhaps not surprising, to see that Regions interpreted the same regulations in quite a different way, although I seem to remember that many ex-GW passing loops were very long with the platforms toward one end and a siding looping off one road toward the other, signalled in such a way that a train from one direction could be admitted (after being checked) into the platform without waiting for the other to be at a stand.

 

It does make me wonder what the procedure on the Highland was, particularly with its predilection for "half-manned" signal boxes at either end of the loop together with setting levers in the booking office?

[The Stationmaster]

Interesting, but perhaps not surprising, to see that Regions interpreted the same regulations in quite a different way, although I seem to remember that many ex-GW passing loops were very long with the platforms toward one end and a siding looping off one road toward the other, signalled in such a way that a train from one direction could be admitted (after being checked) into the platform without waiting for the other to be at a stand.

 

It does make me wonder what the procedure on the Highland was, particularly with its predilection for "half-manned" signal boxes at either end of the loop together with setting levers in the booking office?

 

As a Regulation it was hardly open to interpretation!  The 1960 Regulation was consistent across the whole of BR and is explicit in its wording - in fact it was so explicit that it wasn't altered in structure or meaning when I was a member of the all Regions working party which reviewed and revised the Block Regulations in the 1980s and there was certainly no dubiety or inconsistency of understanding on what the wording meant  and it can readily be traced back to 1920 in exactly similar wording.

 

So I'm reasonably sure that a similar situation existed when the Regulations were revised in 1960 & 1972 and probably in the 1930s as well and almost certainly before then as I can trace no revision of it on the GWR, other than updating the language, since 1911.

 

The fact that the Regulation was seemingly not applied in some places was possibly down to provision in Signalbox Instructions or to poorly supervised and sloppy application - I certainly never came across the former on the Western (which doesn't mean it didn't exist elsewhere of course) but the latter could develop anywhere there wasn't adequate supervision.

 

The existence of long loops is irrelevant (unless modified by Instruction) but as already discussed earlier in this thread the provision of a trap at the leading out end of a crossing loop allowed a completely different situation.

[bécasse]

I agree that the Block Regulations, etc., state "come to a stand". However, in the Rule Book (which is, after all, the senior document), Rule 39 is more explicit and states "has been brought quite or nearly to a stand", so the Rule Book clearly introduces a concept of "quite to a stand" for a train which had come to an absolute standstill.

 

Since I regularly observed homes at crossing loops on the SR being cleared for the second arrival in this way, and since to my personal knowledge SR signalmen were no less responsible than those elsewhere when it came to safe working, it must have been a case of interpretation of the regulations - and this, to me, is the likely explanation - that the Block Regulations were less explicit in defining "stand" than the Rule Book. What they were doing facilitated operation and was no less safe.

[The Stationmaster]

I agree that the Block Regulations, etc., state "come to a stand". However, in the Rule Book (which is, after all, the senior document), Rule 39 is more explicit and states "has been brought quite or nearly to a stand", so the Rule Book clearly introduces a concept of "quite to a stand" for a train which had come to an absolute standstill.

 

Since I regularly observed homes at crossing loops on the SR being cleared for the second arrival in this way, and since to my personal knowledge SR signalmen were no less responsible than those elsewhere when it came to safe working, it must have been a case of interpretation of the regulations - and this, to me, is the likely explanation - that the Block Regulations were less explicit in defining "stand" than the Rule Book. What they were doing facilitated operation and was no less safe.

 

Rule 39 has nothing whatsoever to do with this and is an irrelevance in the working of Home Signals at crossing loops (except as described below) - that, as has been shown above, is clearly and unequivocally dealt with in the relevant Signalling Regulations.  The only possible way of legitimately altering the application of those Regulations is by means of an entry in the Signalbox Special Instructions - end of story.  I or even the Chief Signalling Inspector could - for the sake of debate - tell a Signalman to do it in the way you describe and said Signalman could legitimately report us for instructing him to breach the Regulations (and quite rightly so).

 

However I see you are now talking about the 'second arrival' - do you mean second train to arrive at a Home Signal or second arrival at the station - there is a considerable difference between the two (as the Regulation makes crystal clear).  And of course with the second train to approach the Home Signal after the first has come to a stand in its loop then Rule 39(a) would apply unless the Starting Signal for that train has already been cleared.

[Rick_Skateboard]

Hello,

 

Reviving this old thread.  The layout has changed slightly, I decided to represent one of the places where the Highland Mainline goes from single to double track, rather than just having a passing loop on a single track line.  The fuel sidings are now accessed from the yard, so there is no longer a ground frame.  The double track is going to be absolute block with intermediate blocks between here and the next box.  The single track is going to be tokenless block.

 

 

Some notes to go with the diagram as I have drawn it.  20 lever frame.  The points at each end of the loop (9 and 15) are motored, and have only one lever to operate them, whereas the points into the yard are on rodding with an FPL and points lever (12/13).  No.11 is a yellow disc to allow movements up the yard headshunt when the points are normal.  The disc no.10 reads to the limit of shunt on the down line, for a loco to come off a train in the down platform, get behind no.3 signal and then run round through the up line.  One of the unused levers will be a shunt token release for shunting onto the single line.

 

Does it look ok?  Is the signalling correct?  Does the numbering of the levers make sense?  As usual, any tips appreciated.

 

Cheers

 

Rick     

[Nick C]

Wouldn't 9 be a trailing crossover rather than a facing one? You mention running round a train in the down platform, but it's currently the up one that's bidirectionally signalled. 

 

I'd say, if you're using the down platform for terminating trains, then a trailing crossover, remove #3, add an up advance starter with 10 reading across the crossover to that, and a shunt from the up line back to the up platform, and promote 17 to a full-size arm.

 

Altenatively using the up platform for terminating trains, move 10 across to under 18, reading across the crossover to the down LOS.

[Rick_Skateboard]

Hi Nick,

 

The reason 9 is a facing crossover is to allow a train to be held in the down platform and something else to overtake it via the up platform before going onto the single line, that is also why the up platform is signalled bidirectionally.  This seems to be the arrangement at Dalwhinnie.

 

The trains terminating in the down platform would be freight destined for the yard, and have come from the direction of the single line (Inverness).  After running round they will shunt back out onto the single line and then propel into the yard from signal 16.  This is another reason to allow down trains to pass through the up line, so they can continue running past after a freight has arrived. 

 

Does that make sense?  Do you still think 17 should be a main aspect?

 

Thanks

 

Rick 

[Jeremy Cumberland]

You are right about Dalwhinnie having a facing crossover, but that was presumably so down goods trains could run onto the up line, run round, and then propel into the sidings (which were on the up side). If the crossover was a trailing one then an extra move would be needed. However, at least Dalwhinnie shows that a facing crossover was used in a similar situation.

 

The thing that most struck me was why does the yard have to be there? Any shunting onto the main line requires the single line section, and surely as things stand, you need a main signal at 11 for departing down trains from the yard - or will it never be operated like that? Of course, a main signal at 11 makes little sense, and what you probably want is an advanced starter, but that would change the whole signalling layout at the Inverness end of the station. Better would be to move 13 points so they are the other side of 4, and moving them to the other end of the platform would surely be better still, operationally at any rate, although perhaps geography dictates that the yard needs to be where it is. If you keep the yard at the Inverness end of the station, then making 15 points a crossover will give you a shunting headshunt without using the single line, but I think you would then need another pair of signals, and I don't think you have enough levers. Although you have four spares, 8 and 14 would have been FPLs and you say you want a lever for a shunt token release - something I don't pretend to know anything about.

 

I might add that what I write might be complete gibberish. I enjoy trying to work out how a station might be operated and the signalling plan needed to do so, but there are some genuine experts on this forum, and I am certainly not one of them.

[Rick_Skateboard]

Hi Jeremy,

 

The yard is where it is because I’m loosely basing that end of the layout on Lairg.  So the station is a mash up of Dalwhinnie and Lairg in that respect.  From a model railway point of view I wanted to keep it fairly simple, but with enough operational interest to stop it becoming boring to play with.  I had wondered about whether 11 needed to be a main signal, or whether an advanced starter needed to be provided.  I think your suggestion of putting the points to the yard behind signal 4 makes more sense. 

 

Below is a picture of Lairg.   The disc on the floor is the equivalent of my diagram's No.11, and the signal on the bracket is like my No.4.  I've never fully understood the Lairg signalling, because as you can see there's a main arm and a calling on arm, but I don't know the purpose of the calling on arm?  Is the calling on arm to allow a train to enter the block section for the purposes of a shunt only?  Or does it read to an advanced starter that is out of sight? 

 

Cheers

 

Rick

[Jeremy Cumberland]

I understand your perplexity. Looking at the picture, I wondered if the up starter covered the exit from both the up platform and the yard, but I then found a photograph appearing to show a southbound train leaving the yard with neither signal cleared (although presumably the disk, hidden in this view, is): https://www.railscot.co.uk/img/36/268/. The picture also shows the down home signal. Although the caption says "about to head south", I cannot work out why it should be stopped on the crossover, unless the assembled train is too long to fit into the yard, and there is (or was) some coupling going on off to the left.

 

Another thing to note from the photograph is that there are only three rodding runs heading away from the signalbox, which suggests that the yard crossover does not have an FPL. I cannot work out what arms the home signal has.

 

In your picture, the locomotive is coupling up to the wagons (there is a shunting pole leaning against the first wagon), and from the previous photograph this must be in order to shunt them out onto the single line and back into the sidings, so it is clear that this is the movement the calling on arm is there for, but how it links in with any other signals I cannot say - I have not found a signalling diagram. The 1968 1:2500 map on the Old Maps site only shows one other signal post beyond the down home, about 600 yards away, which I take it to be the down distant.

[beast66606]

2 hours ago, Rick_Skateboard said:

Below is a picture of Lairg.   The disc on the floor is the equivalent of my diagram's No.11, and the signal on the bracket is like my No.4.  I've never fully understood the Lairg signalling, because as you can see there's a main arm and a calling on arm, but I don't know the purpose of the calling on arm?  Is the calling on arm to allow a train to enter the block section for the purposes of a shunt only?  Or does it read to an advanced starter that is out of sight? 

 

 

 

The miniature arm is a shunt ahead - allowing the train to enter the block for as far as required for shunting purposes (ie a train length and a bit beyond the points) only - the train is not to proceed to the next block post, there wont be a starter. This miniature arm and the main arm refer to the main line, not the siding connection

Edited January 8, 2021 by beast66606
typo

[Rick_Skateboard]

Thanks again for the replies, I had previously wondered if it was a signal to shunt into the section, but I didn't know if that was right or not.  This raises a few more questions, please bear with me!  At Lairg, how would the shunt ahead signal be interlocked with the block, which I assume is ETS?  If there is no signal beyond, does that mean a train departing from the yard is entering the block on the authority of the shunt disc only - obviously with the staff too?

 

Does this mean I should have a shunt ahead arm under No.4 on my diagram? And if so, does that work with tokenless block?

 

Another question I've been thinking over is the bracket signal I've got as the up home on my diagram (No.19/17/16) drawn correctly? Should 17 be a main arm? Or should 17 and 16 be miniature arms on the same post reading top to bottom left to right?

 

Cheers,

 

Rick

[Jeremy Cumberland]

I wonder if there is a difference between token working (which I presume is what there was at Lairg) and tokenless working such as you propose for Braeintra.

 

I have never worked on British Rail or its successors, but did for many years work on a single line railway with ETS. Although starting signals were provided for passenger movements (eventually), many regular non-passenger movements had no signal at all, or only had a shunting signal. However, the token itself gave you permission to proceed once you were beyond the last set of points. At Braeintra, the driver won't have a token, so what is to give the driver of a train leaving the yard permission to run through the section? The yellow disk would presumably give permission to enter the section (as does the shunt ahead signal at Lairg) but only for shunting purposes.

 

I imagine that at Lairg, the signalman blocks back before clearing the shunt ahead signal or before clearing the yard exit disc for a shunting movement, and that neither lever is intelocked with the token instrument.

[SZ]

A ground signal can be sufficient to enter and continue through a section.

[Rick_Skateboard]

I would have assumed that in later days, after Highland Railway perhaps LMS/BR, there would have been some level of electrical locking added to the original arrangement that would lock any signal capable of sending you into the section to the token machine?  Perhaps not though!  I think Lairg must have been resignalled/modified at some point; the signals in the picture I posted are LMS type, not Highland. 

 

8 hours ago, Jeremy C said:

I imagine that at Lairg, the signalman blocks back before clearing the shunt ahead signal or before clearing the yard exit disc for a shunting movement, and that neither lever is intelocked with the token instrument.

 

On the tokenless block system there is a physical shunt token that can be released even if the single line is occupied by a train heading away from you, with agreement with the box at the other end of the section.  Or so is my understanding. 

 

2 hours ago, SZ said:

A ground signal can be sufficient to enter and continue through a section.

 

Thanks, that clears that up.

 

Based on what has been discussed up to now, I don't know whether my diagram is correct or not, but it does seem similar to the arrangements at Lairg and Dalwhinnie.  In have started writing up a locking chart for the layout as I have drawn it, which I will post when I think it's far advanced enough to warrant scrutiny.

 

Cheers

 

Rick

[The Stationmaster]

23 hours ago, SZ said:

A ground signal can be sufficient to enter and continue through a section.

Hmm,  this disappeared yesterday for some reasn so it is mnow slighty overtaken but I've added a bit separately  to answer a more e recent question

 

Not for Tokenless block line although it might have been different where tokenless Block was introduced to lines which were already single.  in the early day of Tokenless Block on lines which were reduced from double track to single track HMRI insisted that the Section Signal had to be a colour light signal and would not approve scheme if it wasn't a colour light signal.

 

Clearly the situation in Scotland was different because as far as I am aware semaphore section signals were retained.  Personally I would be inclined to follow the Lairg example where a relatively modern (semaphore) signal has been installed and a regular shunt movement takes place and provide a Shunt Ahead subsidiary.  

 

However the Regulations state that a shunting movement should be dealt with in the same way as a departing trains (i.e.it has to be accepted by the 'box in advance so technically the Section Signal would be free by the block being set to 'Train Accepted' (and so would a Shunt Ahead subsidiary)   But again - where the movement takes place regularly with modern (semaphore) signals I am very much of the view that a shunt Ahead subsidiary would be likely to be provided.

 

 

 

 

Edited January 10, 2021 by The Stationmaster

[The Stationmaster]

20 hours ago, Rick_Skateboard said:

I would have assumed that in later days, after Highland Railway perhaps LMS/BR, there would have been some level of electrical locking added to the original arrangement that would lock any signal capable of sending you into the section to the token machine?  Perhaps not though!  I think Lairg must have been resignalled/modified at some point; the signals in the picture I posted are LMS type, not Highland. 

 

 

On the tokenless block system there is a physical shunt token that can be released even if the single line is occupied by a train heading away from you, with agreement with the box at the other end of the section.  Or so is my understanding. 

 

 

Thanks, that clears that up.

 

Based on what has been discussed up to now, I don't know whether my diagram is correct or not, but it does seem similar to the arrangements at Lairg and Dalwhinnie.  In have started writing up a locking chart for the layout as I have drawn it, which I will post when I think it's far advanced enough to warrant scrutiny.

 

Cheers

 

Rick

On a token based system (unless separate shunting tokens are in use) the Shunt Ahead signa; would not be released by the token because such a signal could be cleared from opposite ends of the section at the same time.

 

On tokenless  - judging by the Regulations - (the set I have doesn't mention shunting 'tokens' but does deal with shunts into the section) there would be a physical release so any associated signal would be released by that.

[Rick_Skateboard]

6 hours ago, The Stationmaster said:

Clearly the situation in Scotland was different because as far as I am aware semaphore section signals were retained.  Personally I would be inclined to follow the Lairg example where a relatively modern (semaphore) signal has been installed and a regular shunt movement takes place and provide a Shunt Ahead subsidiary.  

 

Thanks Mike.  If a shunt disc signal is not sufficient to enter the section on tokenless block, does No.11 on my diagram need to be a full size arm?  Or perhaps it would be better to move the points from the yard back behind no.4, so the disc reads up to a main arm, as Jeremy suggested in a post above.  I guess the shunt disc at Lairg is sufficient to enter the section on ETS working?

 

6 hours ago, The Stationmaster said:

On tokenless  - judging by the Regulations - (the set I have doesn't mention shunting 'tokens' but does deal with shunts into the section) there would be a physical release so any associated signal would be released by that.

 

If my understanding of the Scottish tokenless system is right then the token is released from a lever in the frame.  The lever can only be pulled after a release is given by both boxes.  I’m assuming that pulling the lever would release the physical shunt token and release the signals that read into the block until the token was returned and the release lever put back to normal?  The shunt token lever, no.16, can be seen in this picture of Dalwhinnie.

 

 

Below is the diagram as was, although I changed no.17 to a full size arm.  I'll make some more changes.  I've ordered an MSE lever frame kit today to have a look at, and I think I'll probably try to mock up some interlocking in plasticard to start with.

 

 

Cheers

 

Rick

Edited January 10, 2021 by Rick_Skateboard

[RailWest]

It was certainly the case with the 1967 WR installations of TB that shunt signals could read into the section, but were released by the block, as was the case for instance with Nos 4 and 6 at Templecombe.

[Rick_Skateboard]

12 hours ago, RailWest said:

It was certainly the case with the 1967 WR installations of TB that shunt signals could read into the section, but were released by the block, as was the case for instance with Nos 4 and 6 at Templecombe.

 

It looks like Dunkeld & Birnam on the Highland Mainline has a shunt disc that reads into the section, so it must have been allowed on the Scottish Tokenless Block system.  The diagram is below, the disc is no.12.

 

 

https://www.flickr.com/photos/lickeybanker/49676480758/in/faves-120901503@N04/ the disc can be seen just by the bufferbeam of the 37 in this photo, and has an arrow showing that it is for the siding.

 

Based on that I think I'll keep the no.11 on my layout as it is.  I think if I put a shunt ahead arm under no.4 I'd have to do the same for no.5?

 

Cheers

 

Rick

[Jeremy Cumberland]

4 hours ago, Rick_Skateboard said:

 

It looks like Dunkeld & Birnam on the Highland Mainline has a shunt disc that reads into the section, so it must have been allowed on the Scottish Tokenless Block system.  The diagram is below, the disc is no.12.

 

 

https://www.flickr.com/photos/lickeybanker/49676480758/in/faves-120901503@N04/ the disc can be seen just by the bufferbeam of the 37 in this photo, and has an arrow showing that it is for the siding.

 

Based on that I think I'll keep the no.11 on my layout as it is.  I think if I put a shunt ahead arm under no.4 I'd have to do the same for no.5?

 

Cheers

 

Rick

 

I see that no signal appears to be provided at all for the yard exit, and this helps answer my concern about the plan for Braeintra, which I am looking at very much through the eyes of a driver rather than a signalling engineer.

 

At Lairg (ETS), when the yard exit disc was cleared, the driver would know that, if he had possession of the token, he could run through the section, whereas if he did not, he only had authority to shunt.

 

At Dunkeld, where no signal is provided, the signalman would presumably have to tell the driver what he was authorised to do.

 

At Braeintra, when signal 11 is cleared, the driver cannot tell whether this only enables him to shunt, or whether he has authority to run through the section. Of course, being a disc signal, the driver only has permission to proceed as far as he can see the line is clear, and on that basis it is inadequate as a section signal, but if the signal is there, and it is the only signal there, then it is very easy to see it being used both for shunting and for running through the section, and whatever supplementary instructions there might be for authorising a train from the yard to run through the section would be ignored.

 

4 and 5 at Braeintra I don't see as any problem at all. Clearly they cannot be cleared for shunting movements when the section ahead is not clear, but they are both by the signalbox and the signalman can handsignal any shunting movements past them. However, since both Lairg and Dunblane have shunting signals by your 4, might it be that this is standard practice in this part of the world? Your 5 does not exist at either Dunblane or Lairg.

[RailWest]

>>>I see that no signal appears to be provided at all for the yard exit,....

 

Err....that is what No 11 is for :-) 

[4069]

6 minutes ago, RailWest said:

>>>I see that no signal appears to be provided at all for the yard exit,....

 

Err....that is what No 11 is for :-) 

I think you mean no 12, which is the yard exit signal at Dunkeld.

[RailWest]

19 minutes ago, 4069 said:

I think you mean no 12, which is the yard exit signal at Dunkeld.

Yes...I need to clean my glasses :-)

 

[The Stationmaster]

I think we need to step back a bit and sort some things out - by looking at examples.  Firstly the ScR largely converted token/tablet sections to tokenless working and the signals were unaltered.

 

If you look at the Lairgs photo you can see a Shunt Ahead subsidiary under the main running signal cleared for a shunt move into the section, there is also a disc reading from the sidings nearby - on the left of the picture.

 

On the latest Braeintra diagram No.11 disc clearly reads from the sidings, so it cannot apply to a shunting movement made past Signal No.4 - which puts uyou back into the question of deciding whether or not you require a Shunt Ahead subsidiary beneath either or both of signals No's 4 & 5.  As there is an acceptance required for a movement past those signals you could get away without a Shunt ahead subsidiary and you will undoubtedly find example sof that 'somewhere in Scotland.  

 

And lo and behold Dunkeld gives exactly such an example.  To make a shunt move to the sidings it can only take place from the bidirectional line and the only signal there to signal such a movement is No.3 running signal, it has no Shunt Ahead arm.  Disc 18 will obviously take the shunt move back into the sidings but - if the locking is modern - will also read towards signal No.20 and possibly back into the reversible line (maybe governed by track circuit controls?).  Disc No.12 is an exact equivalent, albeit with a red arm instead of yellow, of No.11 at Braeintra and reads from the siding and is shown to have a Line Clear Release (LCR)

 

Quite what the Shunting Lever at Dunkeld does is unclear to me but in theat lever frame photo there is obviously an interlocking/acceptance lever of some sort (because of its colour) and it is noticeable on the Dunkeld diagram that that there is a Shunting Lever in one direction and a shunting key in the opposite direction.  Their numbering might suggest that the Shunting Lever is used in order to make a shunt past Signal No.5 and the Shunting Key could possibly be involved with a movement in the opposite direction but it does seem over-complicated and might well be something that was done in Scotland to achieve a similar sort of flexibility to that offered by the old Electric Token etc Regulations or to avoid problems with resetting the block after a shunt had been made?

 

The original ScR Tokenless Block Regulations had some features which were unique to Scotland but I suspect that the 'Shunting Key' was some sort of equivalent to the 'Train Arrived' button on the instrument (and might also have reset the treadle as well?).