Upcoming Games


Full list
Add a game

Upcoming Events

We are not planning any more in-person events until the COVID-19 situation has improved.

Who's Online

Soton_Speed, PN40, BarryM, y10g9, zachpratt (5 users seen recently)

St. Andrews signalling questions

You are here: Home > Forum > Simulations > Released > Bristol > St. Andrews signalling questions

Page 1 of 2

St. Andrews signalling questions 01/07/2020 at 22:39 #128756
slugsix
Avatar
18 posts
I have some detailed questions about some of the St. Andrews Road signals, having watched a cab ride video of the Severn Beach Line.

SA7 is located just the Avonmouth side of St. Andrews Road LC. It acts as the section signal for Severn Beach, so once a train is signalled past SA7 for Severn Beach, no other trains can be in that same section, or signalled across that route at Holesmouth Jcn. SA7 is a 3 aspect CL - RYG.

Just before Holesmouth Jcn, there is a further signal on the route to Severn Beach. SA47. Looking at the cab ride video, this signal is two aspect CL, with a feather for taking the route to Filton. SA47 is the last signal before the Severn Beach fixed distant board.

On the cab ride video, SA47 shows GREEN. But what is the other aspect? Red wouldn't quite make sense for two reasons. The first is that SA7 is the section signal, and so there would normally be no reason to hold a Severn Beach train at SA47. The second reason is that if the other SA47 aspect is RED, then there cannot be a YELLOW aspect, and thus trains signalled from here up the Filton line, could never be given a RED at the following signal on the Filton line, which is SA37 which is three aspect.

I'm therefore guessing that the other aspect of SA47 is YELLOW, and that this signal NEVER shows RED? Severn Beach trains always get a GREEN here, whilst trains for Filton from Avonmouth can get a GREEN if SA37 is OFF, or YELLOW if SA37 is ON (both with the feather lit).

To add to the mix, the signal at the top of the BP/Bennetts siding, SA45 is 3 aspect, but doesn't have a feather, even though physically (by trackwork) there are two routes from it - Severn Beach and Filton. I'm therefore guessing here, that due to SA7 being the section signal, there is no signalled route from SA45 to the Severn Beach line, and thus, the only route is to Filton. Thus SA45 does not need a feather.

It's a really unusual set up! Can anybody confirm my guesses are right, particularly with respect to SA47.

Another interesting signal is SA5 which sits on the end of the platform at Avonmouth in the Severn Beach direction. This signal is 2 aspect but displays either RED or YELLOW. The next signal along is SA7, which as we've already seen is a 3 aspect RYG. I think the reason for this is the 15mph curve between the two signals, which actually mean there is no point in SA5 displaying a GREEN - this in turn allows the St. Andrews Road LC to be lowered later.

Log in to reply
The following user said thank you: DaveHarries
St. Andrews signalling questions 01/07/2020 at 23:11 #128759
GeoffM
Avatar
5218 posts
SA7 is a two-aspect R/G signal but mounted in a 3 aspect head with the yellow blanked off. Oddly I can't find any evidence of a repeater or fixed distant board before SA47. In any case, a train can be held at SA47 as it's a controlled signal capable of red and green only, capable of routing to Severn Beach or to SA37 (which must be off for SA47 to show proceed).

SA45 is a 3-aspect R/Y/G with no such requirement on SA37 being off, presumably due to the low line speed compared to SA47. I can't find a route table for that signal but SA38 has no route to behind SA45 so presumably there is no access from SA45 to behind SA38.

SA5 is indeed R/Y.




Post has attachments. Log in to view them.
SimSig Boss
Last edited: 01/07/2020 at 23:16 by GeoffM
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 00:08 #128761
DaveHarries
Avatar
1045 posts
I feel like throwing my hat in here seeing as the Bristol Temple Meads to Severn Beach route is my local line. How can SA7 be the section signal? At Crowcombe Heathfield (WSR) the section signal is the last signal that the driver sees before he gets to the home signal of either Williton SB or Bishops Lydeard SB. I would have thought that, if we apply that principle here, surely SA47 should be the section signal not SA7? I may do some research.

If the Avonmouth Docks area still had mechanical signalling it would probably be easier to work out but Avonmouth Docks Jcn and Holesmouth Jcn were lost in 1988 with St. Andrews taking control of both: the latter box is, I believe, now in use at Bodmin General (B&WR).

Dave

Last edited: 02/07/2020 at 00:11 by DaveHarries
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 00:10 #128763
JamesN
Avatar
1267 posts
It’s track circuit block, so there is no home or section signal
Last edited: 02/07/2020 at 00:11 by JamesN
Reason: None given

Log in to reply
The following users said thank you: DaveHarries, jc92, Stephen Fulcher
St. Andrews signalling questions 02/07/2020 at 00:13 #128764
jc92
Avatar
3081 posts
DaveHarries in post 128761 said:
At Crowcombe Heathfield (WSR) the section signal is the last signal that the driver sees before he gets to the home signal of either Williton SB or Bishops Lydeard SB.
Do the WSR not have distant signals?

Log in to reply
St. Andrews signalling questions 02/07/2020 at 00:24 #128765
pedroathome
Avatar
645 posts
My understanding is that, until the BHT opened, you had SA7 which could show Red / Yellow, reading onto SA9 (R/G), which was somewhere very close to the box, which would have been the last signal before Severn Beach. SA9 most likely placed for the driver to pick up a token before proceeding to the beach.

As to the immediate question in hand, Theres no need for a repeater here, because for SA7 to show a proceed aspect, SA47 needs to be first showing a proceed aspect. (This is my understanding anyhow)

(I feel that I have repeated some information already given, so if so, please disregard)

James

Log in to reply
St. Andrews signalling questions 02/07/2020 at 00:25 #128766
JamesN
Avatar
1267 posts
SA45 (which is the exit signal for the BP terminal) only has a route to SA37 - you can’t get to Severnside or Severn Beach from BP - it’s got a yellow so no need for SA37 to be off

AFAIK SA47 is only a “backing” signal - if you could set route SA7 - SA47 - SA37 (and they’re on two different panels in St Andrews box so I’m not sure you can), SA7 will never clear - it’s provided so a train can come down the Beach branch and reverse behind SA47 to head towards Hallen Marsh

Last edited: 02/07/2020 at 00:26 by JamesN
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 01:32 #128770
GeoffM
Avatar
5218 posts
JamesN in post 128766 said:
AFAIK SA47 is only a “backing” signal - if you could set route SA7 - SA47 - SA37 (and they’re on two different panels in St Andrews box so I’m not sure you can), SA7 will never clear - it’s provided so a train can come down the Beach branch and reverse behind SA47 to head towards Hallen Marsh
7-47-37 is certainly possible. Look at the picture I provided. It's also how Cross Country trains got around the Filton engineering works some time ago.

SimSig Boss
Log in to reply
St. Andrews signalling questions 02/07/2020 at 09:37 #128776
slugsix
Avatar
18 posts
Thanks for your help Geoff.

I don't believe that SA47 can ever display a RED to trains that have passed SA7 at GREEN. (From the cab ride video the YELLOW on SA7 doesn't appear to be blanked, but I wouldn't bet on that because the quality of the picture isn't good enough to be sure. It may also be that it just doesn't have the capability of displaying YELLOW).

For trains heading to Severn Beach from Avonmouth, there is no meaning to SA47 at RED. It's a one train section all the way from SA7 to Severn Beach. So with SA7 passed at GREEN, SA47 must be presented at GREEN. There is no repeater for SA47 after SA7, so having SA47 at RED having passed SA7 at GREEN would be a bit dodgy!

For trains from the BP siding SA45 also makes sense. You cannot signal to the Beach line from SA47, and so RED, YELLOW and GREEN all make sense. SA37 can be RED from SA45 since SA45 can display YELLOW.

SA47 however cannot display YELLOW and so SA37 must be YELLOW/GREEN for SA47 to display GREEN with a feather (position 4). So to clear a train from Avonmouth to Filton past SA7, SA37 must be OFF, enabling SA47 to show GREEN and SA7 thus will also show GREEN.

So the question remains - what is SA47's RED actually for? The answer, as Geoff said, must be for reversals. One example would be the Severnside binliner. Top 'n' Tailed, it has to cross Holesmouth Junction and presumably comes down from Filton and reverses at SA47. In this case the RED of SA47 comes into play, the signal only displaying GREEN once the junction has be set for the correct route. The same would be true in reverse.

In this case, I wonder if the signaller still has to set the route from SA7 (which may mean the LC barriers would have to be lowered??).....

Geoff is right, diversions have used the route SA7 - SA47 - SA37 in the past. Passenger and freight. Like I said I think the Severnside SITA train can also reverse here.

Finally, the Sectional Appendix has something to say on it too:

"One train only working arrangements - The ‘One Train Working’ single line section for trains operating along the Main Line between St. Andrews Junction and Severn Beach commences at signal SA7 near St. Andrews Level crossing. Signal SA7 is the ‘controlling signal’ for the purposes of Rule Book, Module TW1, Section 32 instructions.

It is not possible to signal trains between the Down and Up Branch lines and Hallen Marsh Junction or the BP Terminal with a train already occupying the single line section to Severn Beach.

For non-passenger trains signalled from between Hallen Marsh Junction and the Down and Up Branch lines the
regulations for signalling trains by the Track Circuit Block system apply. Rule Book, Module TW1, Section 30 applies to the signalling of passenger trains on this route and special instructions must be implemented."

Log in to reply
St. Andrews signalling questions 02/07/2020 at 11:55 #128782
clive
Avatar
2134 posts
You need to look at the diagrams that Geoff has provided. They will be authoritative.

SA7 doesn't have a yellow aspect. Therefore the green can't be providing information about the state of SA47. I don't know if there's a repeater or fixed distant or whether drivers are just supposed to know about this. But see below.

SA47 *has* to be able to show red because it protects a junction. There is no way that an arrangement that has it showing yellow while the points move would be acceptable. I don't know whether SA7 is held at red until SA47 is cleared - there's no info box in Geoff's extract - though it seems a long distance for this. If SA7 had a yellow there would be too much chance of the driver forgetting the aspect.

The table says that SA47 can't clear with the feather unless SA37 is at least yellow.

If I'm interpreting your quote from the Sectional Appendix correctly, it may well be that SA7 can't clear with SA47 at red. Drivers should still keep any eye open for SA47 being red in case of an emergency or failure.

Log in to reply
St. Andrews signalling questions 02/07/2020 at 12:25 #128783
Tempest Malice
Avatar
88 posts
I would add that the sectional appendix was updated (back in october 2018 if the update date on the section is to belived) to now state:
NR said:
The ‘One Train Working’ single line section for trains operating along the Main Line between St. Andrews Junction and Severn Beach commences beyond 138A points at Holesmouth Junction. Signals SA47 and SA45 are the ‘protecting signals’ for the purposes of Rule Book, Module TW1, Section 32 instructions.It will be possible to signal trains between the Down and Up Avonmouth Dock Lines and Hallen Marsh Junction or the Avonmouth PBA sidings with a train already occupying the single line section to Severn Beach.

So I would imagine that something (though I have no knowledge of what) has possibly changed with how this junction is worked since slugsix read their older copy of the sectional appendix. (which may (though I don't think it is too likely) mean that SA7 could now have a yellow and geoff's diagrams may possibly be put of date.)

Log in to reply
St. Andrews signalling questions 02/07/2020 at 13:05 #128786
slugsix
Avatar
18 posts
Clive, I *have* looked at the diagrams.

There is no repeater between SA7 and SA47 - the signal box diagrams do not show one, the cab ride video does not show one and I travel on that line regularly and cannot see one.

The conclusion is that when SA7 shows GREEN and the road is set for Severn Beach then SA47 must also show GREEN. It cannot show red - unless there is, as you say an emergency.

Similarly, if the road is set for Filton (via Hallen), then if SA7 shows GREEN, then SA47 must also show GREEN, and also SA37 must be OFF.

It is therefore impossible, under normal circumstances, to approach SA47 at RED having passed SA7, which must have shown GREEN (because it doesn't have a YELLOW).

The only case where a driver can encounter SA47 at RED, therefore, is during a reversing move, when the signal is held at RED until the junction is been set. Nobody is saying the points will move when it has a YELLOW - because as the diagrams show, it doesn't have a YELLOW. (Emergencies, failures excepted of course).

clive in post 128782 said:
You need to look at the diagrams that Geoff has provided. They will be authoritative.

SA7 doesn't have a yellow aspect. Therefore the green can't be providing information about the state of SA47. I don't know if there's a repeater or fixed distant or whether drivers are just supposed to know about this. But see below.

SA47 *has* to be able to show red because it protects a junction. There is no way that an arrangement that has it showing yellow while the points move would be acceptable. I don't know whether SA7 is held at red until SA47 is cleared - there's no info box in Geoff's extract - though it seems a long distance for this. If SA7 had a yellow there would be too much chance of the driver forgetting the aspect.

The table says that SA47 can't clear with the feather unless SA37 is at least yellow.

If I'm interpreting your quote from the Sectional Appendix correctly, it may well be that SA7 can't clear with SA47 at red. Drivers should still keep any eye open for SA47 being red in case of an emergency or failure.

Log in to reply
St. Andrews signalling questions 02/07/2020 at 13:07 #128787
slugsix
Avatar
18 posts
Indeed. Several modifications were made recently, although I'm not particularly interested in them, because it's not the period I'm interested in. For example, modifications were made in the Clifton area that allows trains to be routed into either platform from Redland.

I've seen a document about all the changes that were made, so maybe it mentions something about St. Andrews which may shed some more light on it.....

Tempest Malice in post 128783 said:
I would add that the sectional appendix was updated (back in october 2018 if the update date on the section is to belived) to now state:
NR said:
The ‘One Train Working’ single line section for trains operating along the Main Line between St. Andrews Junction and Severn Beach commences beyond 138A points at Holesmouth Junction. Signals SA47 and SA45 are the ‘protecting signals’ for the purposes of Rule Book, Module TW1, Section 32 instructions.It will be possible to signal trains between the Down and Up Avonmouth Dock Lines and Hallen Marsh Junction or the Avonmouth PBA sidings with a train already occupying the single line section to Severn Beach.

So I would imagine that something (though I have no knowledge of what) has possibly changed with how this junction is worked since slugsix read their older copy of the sectional appendix. (which may (though I don't think it is too likely) mean that SA7 could now have a yellow and geoff's diagrams may possibly be put of date.)

Log in to reply
St. Andrews signalling questions 02/07/2020 at 13:28 #128791
slugsix
Avatar
18 posts
Sadly, the document I found was only in respect of the signalling changes as far as Clifton.

It looks to me as though the single line section to Seven Beach has now been moved to beyond SA47, and as the newer SAs state, SA45 and SA47 are now the protecting signals. This, as you say, probably means that SA7 is now capable of displaying a YELLOW aspect and Geoff's diagrams are older and no longer refer to the current state of affairs.

I'm not sure SA47 is still two aspect. The cab ride video I have doesn't have a specific date, other than "Copyright 2005". SA47 could well be three aspect now, which would remove the need for SA37 to be OFF before SA47 is cleared for a route to Filton.

slugsix in post 128787 said:
Indeed. Several modifications were made recently, although I'm not particularly interested in them, because it's not the period I'm interested in. For example, modifications were made in the Clifton area that allows trains to be routed into either platform from Redland.

I've seen a document about all the changes that were made, so maybe it mentions something about St. Andrews which may shed some more light on it.....

Tempest Malice in post 128783 said:
I would add that the sectional appendix was updated (back in october 2018 if the update date on the section is to belived) to now state:
NR said:
The ‘One Train Working’ single line section for trains operating along the Main Line between St. Andrews Junction and Severn Beach commences beyond 138A points at Holesmouth Junction. Signals SA47 and SA45 are the ‘protecting signals’ for the purposes of Rule Book, Module TW1, Section 32 instructions.It will be possible to signal trains between the Down and Up Avonmouth Dock Lines and Hallen Marsh Junction or the Avonmouth PBA sidings with a train already occupying the single line section to Severn Beach.

So I would imagine that something (though I have no knowledge of what) has possibly changed with how this junction is worked since slugsix read their older copy of the sectional appendix. (which may (though I don't think it is too likely) mean that SA7 could now have a yellow and geoff's diagrams may possibly be put of date.)

Log in to reply
St. Andrews signalling questions 02/07/2020 at 13:42 #128792
slugsix
Avatar
18 posts
Here you go folks. The document below confirms that SA7 could only be cleared if SA47 was clear. SA47 is now likely to be a 3 aspect signal, whereas before it was 2A. Given that SA47 is now the protecting signal, it is also highly likely that SA7 is now 3 aspect also.

https://s3-eu-west-1.amazonaws.com/travelwest/wp-content/uploads/2015/07/9-grip2-app-h-signalling-feasibility-report.pdf

(As I said, I'm more interested in the period before these alterations took place, although they are still interesting to discuss).

Last edited: 02/07/2020 at 13:43 by slugsix
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 14:17 #128794
pedroathome
Avatar
645 posts
I have been thinking it through, and I have a few thoughts here. This is all speculation, so take with a pinch of Sodium Chloride.

Firstly, A 3 aspect signal head dosen't mean that the signal can display all three aspects. Given that the rest of the St Andrews area is all three aspect, its possible that they used another three aspect head on a two aspect signal to cut down on costs.

Secondly (And this is the long bit), Having two panels in the box, to me suggests that something is at play here. Before the BHT opened, you had St Andrews OCS Panel which just controlled the loops at Avonmouth, and the single line towards Severn Beach. At the time, it is my understanding that this was token worked, and that a token would be needed to access the BP terminal or the siding at Severn Beach.

Based on this, I suspect that the new panel which was added for the BHT in St Andrews Panel was done such that it was all installed in the former token section, therefore requiring as little modifications to the existing setup as possible (Feeding some track indications back, or removing the token system, that kind of idea).

If SA7 was to be made a three aspect signal, so it could read Yellow onto SA47, I would assume that this would have added extra expense for very little benefit. Most likely, they never considered the possibility of trains doing anything other than Avonmouth to Severn beach along that stretch. Possibly with the signalled route being added as an afterthought.

In relation to SA47, after having written some midland sims, and considering the slotting arrangement from Wigan Wallgate to Warrington PSB, (Please see image in this post https://www.simsig.co.uk/Forum/ThreadView/50882?postId=128404), that SA47 almost acts like a route setting slot, all be it, capable of showing an aspect.

Finally, that file you have liked to is all proposals. There is nothing I've seen to suggest that anything on the Avonmouth to Severn Beach area has been changed in any way

James

Last edited: 02/07/2020 at 14:17 by pedroathome
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 14:59 #128796
JamesN
Avatar
1267 posts
SA7 is still only capable of showing Red and Green aspects to this day
Log in to reply
The following user said thank you: Stephen Fulcher
St. Andrews signalling questions 02/07/2020 at 15:07 #128797
slugsix
Avatar
18 posts
You are incorrect to suggest that the rest of St. Andrews was all 3 aspect. It was not.

SA2R - 2A Y/G
SA2 - 2A ?/?
SA3R - 2A Y/G
SA3 - 2A R/Y
SA4 - Could be 2 aspect, difficult to tell from Cab ride
SA8 - 2A R/G
SA38 - 2A R/G
SA47 - 2A R/G

To list just those I know of.

You are correct that the document I linked to are the proposals. However, it alludes to how things used to work - particularly in section 3.1.6 where it states about SA7 requiring SA47 to be clear before it can be cleared.

Has one of the proposals (or a modification) now become reality? The sectional appendix has changed and now describes SA47/SA45 as the controlling signals for the single line to Severn Beach. Does that now mean that SA47 can now display a RED to Severn Beach Trains - that would in turn imply SA7 must now be capable of displaying a YELLOW to them.

If that were true, then I suspect, both SA47 and SA7 are now three aspect. If no changes have taken place, then it would be as Geoff provided, with the additional condition that SA7 can't be cleared until SA47 has also been cleared. But why then, the change to the Sectional Appendix wording?

Geoff - are you able to provide diagrams for SA4 and SA2 please?

pedroathome in post 128794 said:
I have been thinking it through, and I have a few thoughts here. This is all speculation, so take with a pinch of Sodium Chloride.

Firstly, A 3 aspect signal head dosen't mean that the signal can display all three aspects. Given that the rest of the St Andrews area is all three aspect, its possible that they used another three aspect head on a two aspect signal to cut down on costs.

Secondly (And this is the long bit), Having two panels in the box, to me suggests that something is at play here. Before the BHT opened, you had St Andrews OCS Panel which just controlled the loops at Avonmouth, and the single line towards Severn Beach. At the time, it is my understanding that this was token worked, and that a token would be needed to access the BP terminal or the siding at Severn Beach.

Based on this, I suspect that the new panel which was added for the BHT in St Andrews Panel was done such that it was all installed in the former token section, therefore requiring as little modifications to the existing setup as possible (Feeding some track indications back, or removing the token system, that kind of idea).

If SA7 was to be made a three aspect signal, so it could read Yellow onto SA47, I would assume that this would have added extra expense for very little benefit. Most likely, they never considered the possibility of trains doing anything other than Avonmouth to Severn beach along that stretch. Possibly with the signalled route being added as an afterthought.

In relation to SA47, after having written some midland sims, and considering the slotting arrangement from Wigan Wallgate to Warrington PSB, (Please see image in this post https://www.simsig.co.uk/Forum/ThreadView/50882?postId=128404), that SA47 almost acts like a route setting slot, all be it, capable of showing an aspect.

Finally, that file you have liked to is all proposals. There is nothing I've seen to suggest that anything on the Avonmouth to Severn Beach area has been changed in any way

James

Last edited: 02/07/2020 at 15:19 by slugsix
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:09 #128798
slugsix
Avatar
18 posts
Then why has the sectional appendix wording changed? Or has something else happened?

The current SA has been modified and now reads:

"One train only working arrangements - The ‘One Train Working’ single line section for trains operating along the Main Line between St. Andrews Junction and Severn Beach commences beyond 138A points at Holesmouth Junction. Signals SA47 and SA45 are the ‘protecting signals’ for the purposes of Rule Book, Module TW1, Section 32 instructions."

Doesn't that mean that SA47 can now be held at RED. If that were the case, then the proceeding signal would have to display YELLOW. That proceeding signal is SA7???

The previous SA wording can be found above. In that case SA7 was the protecting signal and could only be cleared if SA47 was cleared.

So what has changed to make the SA wording change?

JamesN in post 128796 said:
SA7 is still only capable of showing Red and Green aspects to this day

Last edited: 02/07/2020 at 15:21 by slugsix
Reason: None given

Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:17 #128799
JamesN
Avatar
1267 posts
No, you’re overthinking it

SA47 can show Red, correct, and is the nominated signal as far as the OTW rules are concerned.

But none of that means that SA47 is approachable at Red. The prior interlocking of 7 requiring 47 off still applies, and hasn’t been changed in about 30 years since the new panel was put in for Avonmouth BHT.

Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:19 #128800
pedroathome
Avatar
645 posts
slugsix in post 128797 said:
You are incorrect to suggest that the rest of St. Andrews was all 3 aspect. It was not.

SA2R - 2A Y/G
SA2 - 2A ?/?
SA3R - 2A Y/G
SA3 - 2A R/Y
SA4 - Could be 2 aspect, difficult to tell from Cab ride
SA8 - 2A R/G
SA38 - 2A R/G
SA47 - 2A R/G

To list just those I know of.

James
[/quote]

Sorry, I meant the new panel, which did not control the Avonmouth Station area. The avonmouth station area was done around 1985, the BHT around 1992

Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:25 #128801
slugsix
Avatar
18 posts
No. I'm not. I get that SA47 can show RED. I also get that SA7 can only be cleared only when SA47 has cleared. Clearly because that what I worded in one of my earlier posts.

The question now, is why did the Sectional Appendix wording changed if nothing has changed, as you say, for 30 years? What was the driver for that?

That's not overthinking. That's a reasonable question.

JamesN in post 128799 said:
No, you’re overthinking it

SA47 can show Red, correct, and is the nominated signal as far as the OTW rules are concerned.

But none of that means that SA47 is approachable at Red. The prior interlocking of 7 requiring 47 off still applies, and hasn’t been changed in about 30 years since the new panel was put in for Avonmouth BHT.

Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:33 #128802
JamesN
Avatar
1267 posts
It looks to have changed wording around the same time as the rail connection into the Severnside waste terminal was commissioned - as the rail connection is within the OTW section as a GF with lock in capabilities, perhaps it was changed to allow a train to enter the OTW section via a reversal at SA47 - otherwise technically would it not always have to route via Clifton?
Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:48 #128803
slugsix
Avatar
18 posts
Yes, that would make sense. It would also pave the way for the proposed changes in the future.

However, if, as the SA states SA47 is the controlling signal, does that not mean that now it's capable of being approached at RED? Or perhaps, more likely, they are able to change the signals in the future so that's what happens. The OTW working now only exists beyond SA47 (or more precisely the 138A points)? That also implies that SA7 to SA47 is now (or could at least become) a signal section? I'm guessing that that could be the future intention that hasn't been implemented just yet? That all makes sense doesn't it?

As an aside, are you able to confirm the number/colour of aspects of SA2 and SA4? Maybe Geoff has diagrams for those two as well?

JamesN in post 128802 said:
It looks to have changed wording around the same time as the rail connection into the Severnside waste terminal was commissioned - as the rail connection is within the OTW section as a GF with lock in capabilities, perhaps it was changed to allow a train to enter the OTW section via a reversal at SA47 - otherwise technically would it not always have to route via Clifton?

Log in to reply
St. Andrews signalling questions 02/07/2020 at 15:57 #128804
JamesN
Avatar
1267 posts
No, the changed wording the the Sectional doesn’t mean SA47 is approachable at Red - and although it would open up that possibility in future, you don’t gain anything service-wise by permitting it with the current track layout.

Both SA2 and SA4 are 3 aspect. I have drawings, but no way of uploading them from work

Log in to reply