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scottystitch

Signaling and Turnouts at the exit from Tunnels

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I have a question for the signalling/PW experts.

 

My layout imagines a tunnel at about 3/4 of a mile long.  There is a set of turnouts 111ft from the tunnel portal which is the start of the station approach pointwork. Would the signal protecting the turnouts be on exit from the tunnel, in the tunnel or at the entry to the tunnel at the other end? 

 

Time frame is 1962-64, with recently commissioned colour light signals and theatre boards.

 

Best

 

Scott

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I was thinking about this very issue recently and the situation you describe exists at the south end of Guildford station. The last signal prior to the station is a short distance after the tunnel (Chalk tunnel, 845 yards). You can see it from the cab from 27m25s in this video: 

 

https://m.youtube.com/watch?v=bxVu99xCP5Q

 

In reality the distance there is probably more than 111ft but with the compression we routinely accept on our layouts, I’m sure your situation would be ok.

Edited by Western Aviator
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5 minutes ago, luckymucklebackit said:

I am thinking Glasgow Queen Street as a prototype example, in which case the signals would be ground positioned in the tunnel.

 

Jim

Thanks Jim. 

 

As in not a three aspect Red Yellow Green then, but a conventional ground signal?

 

Best


Scott

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The Down signal for Continental Jct, Dolland's Moor is very close to the Eastern portal of Saltwood Tunnel. There is a repeater at the Western portal.

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It would be a conventional multi aspect head mounted at ground level with the red at the top. A theatre indicator would also be ground mounted 10 yards beyond the signal.

Is it a terminus or through station?

 

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56 minutes ago, TheSignalEngineer said:

It would be a conventional multi aspect head mounted at ground level with the red at the top. A theatre indicator would also be ground mounted 10 yards beyond the signal.

Is it a terminus or through station?

 

Thank you.

 

It is a through station.

 

Best

 

Scott

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The up slow at primrose hill the signal is in the tunnel, Ipswich on the down both lines bi di the signal is opposite end of the tunnel.  Canonbury the signal is a full sized one stood midway through  the tunnel 

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The Up Stour at New Street has a four aspect with subsidiary aspect and a theatre indicator.

4 hours ago, russ p said:

The up slow at primrose hill the signal is in the tunnel, 

Not sure what's there now but it used to be a smaller head than standard due to clearance problems.

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Salisbury Tunnel Junction has point blades almost in the tunnel mouth with the (now former) signalbox beyond in the fork of the main and branch routes.  IIRC there was a banner repeater before the tunnel with a small ground-level "traffic light" within the tunnel although in situations such as this both bobby and driver would try to avoid bringing a train to a stand within tunnel limits.  The longer you stood emitting fumes (be they steam, smoke or diesel exhaust) the less pleasant it was for crew and passengers never mind the obligation to remind the signaller of your presence in some locations. 

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The junction at Crystal Palace (LL) goes one step further as the point ends are inside the tunnel (although the crossings are outside), along with the junction signal. There is even a section chiselled out ofthe tunnel lining to accommodate parts of the point machine, as it has to sit between that and the running line.

 

There is also the example of Glasgow Queen Street (HL), where I believe the crossovers are completely inside the tunnel.

 

There were, in an earlier era, some interesting combinations of tunnels, points and signals on the lines leading down to the Liverpool Docks, with at least one example (Canada Dock?) where the signals were immediately outside the tunnel portal but the point ends were inside.

 

Jim

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Thanks to everyone who replied, it's all very enlightening. Based on what some of you have said, it would seem to be acceptable to imagine that the signal is within the tunnel, and therefore not incorrect to not have one at the exit mouth.

 

Best


Scott

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Re: Glasgow Queen St., there is a signalling diagram available at s-r-s.org from the 1985 Cowlairs resignalling 

https://www.s-r-s.org.uk/pullfree.asp?FilePath=ArchiveSignals\Downloads\brscot&FileName=1985-cowlairs.pdf

(Diagram on the last page)

 

Not sure when it changed but the crossover 187/188 used to be a scissors. Note, heading into the station you have 3-aspect YGY then 2-aspect RY, the latter having a GPL and theatre indicator.

You also have GPL + theatre just outside the tunnel mouth.

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12 hours ago, TheSignalEngineer said:

The Up Stour at New Street has a four aspect with subsidiary aspect and a theatre indicator.

Not sure what's there now but it used to be a smaller head than standard due to clearance problems.

 

Indeed there are two signals in the tunnels approaching New St from Wolverhampton. Admittedly one was outside till the NIA was built. 

 

Snow Hill has signals at the approach to the tunnel from Moor St

 

Worcester has signals (Semaphore) outside the far end of the tunnel before reaching Tunnel Jn.

 

The positioning of the signalling would depend on many factors relating to the operation of the station and the necessary signalling design principles in use at the time of installation.  Main running signals in tunnels are not that common I would say but anything is possible. 

 

Andy

 

 

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Spot on re Worcester SM42!

 

Heres the signals north of Rainbow Hill Tunnel

 

000038.JPG

 

And heres the pointwork they protect the other end of the tunnel

 

http://www.miac.org.uk/class03.html#brd2122

 

Tunnel length 212 yards. 

 

Cheers

 

Phil

Edited by Phil Bullock
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3 hours ago, scottystitch said:

Thanks to everyone who replied, it's all very enlightening. Based on what some of you have said, it would seem to be acceptable to imagine that the signal is within the tunnel, and therefore not incorrect to not have one at the exit mouth.

 

Best


Scott

The moves ahead of the signal would determine whether or not the signal could be in the space outside the tunnel. A sketch of the layout is needed, together with line speed for through non-stop trains and the planned traffic pattern, to give a definitive answer. 

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12 hours ago, jim.snowdon said:

There is also the example of Glasgow Queen Street (HL), where I believe the crossovers are completely inside the tunnel.

The signal on the Up Stour at New Street has a trailing crossover immediately beyond it inside the tunnel. 

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9 minutes ago, TheSignalEngineer said:

The moves ahead of the signal would determine whether or not the signal could be in the space outside the tunnel. A sketch of the layout is needed, together with line speed for through non-stop trains and the planned traffic pattern, to give a definitive answer. 

 

Hopefully a plan of the approach is attached.

 

Platforms 1 and 3 are through Down platforms

 

Platforms 2 and 4 are through UP platforms (2 is to be signalled bidirectional but this would be used sparingly)

 

Platforms 5, 6 and 7 are UP facing bays.

 

The two sidings at the very top are UP facing motorail bays.

 

Line speed for all traffic is maximum 30MPH

 

There are no slips, only two diamond crossings.

 

 

Perth_Caledonian_Code_40_V5A__Alternate_Southern_Approach_Zoom.jpg

Edited by scottystitch

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Thanks, will look later when on a big screen. First impression is signal in tunnel  but that could depend on what the trailing crossover is used for.

Edited by TheSignalEngineer

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Have a look at Bangor (North Wales); It's plan is simplified version of your track plan. The signal box diagram is about half-way down this page:

http://www.6g.nwrail.org.uk/signallingoverwales.htm

 

Repeaters are used in Belmont Tunnel to help protect the two shunt moves on the down main (into the yard and using the crossover to access the up main). There's a repeater on the entrance to Bangor Tunnel to show the status of the signal at the tunnel exit.

 

Steven B.

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33 minutes ago, TheSignalEngineer said:

Thanks, will look later when on a big screen. First impression is signal in tunnel  but that could depend on what the trailing crossover is used for.

 

The trailing crossover is for shunting of stock between platforms/sidings.

 

Best


Scott

 

Actually ignore that.

 

Rather embarrassingly, I've just realised this approach will not work as there is no way for down trains to access platform three.  I suspect it will be a case of making the trailing crossover a facing one, but I'll need to look at it properly. I'm not sure what I was thinking there.

 

Best


Scott

Edited by scottystitch

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26 minutes ago, scottystitch said:

Rather embarrassingly, I've just realised this approach will not work as there is no way for down trains to access platform three.  I suspect it will be a case of making the trailing crossover a facing one, but I'll need to look at it properly. I'm not sure what I was thinking there.

 

Scott,

 

Could you not make the upper turnout of the crossing connecting platforms 5 and 6 into a 3-way turnout, to provide a second crossing connecting the approach to platform 6 with platform 3?

 

Sadly I can't help with the signalling, but it's an interesting discussion.

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20 minutes ago, Dungrange said:

 

Scott,

 

Could you not make the upper turnout of the crossing connecting platforms 5 and 6 into a 3-way turnout, to provide a second crossing connecting the approach to platform 6 with platform 3?

 

Sadly I can't help with the signalling, but it's an interesting discussion.

Or make the next one to the right into a single slip? P3 also doesn't need to join onto P4/up main either?

 

I also don't see any way for down trains to enter P2, which is stated to be bidirectionally signalled.

 

While it would obviously depend on the prototype, the trackwork could be simplified a lot whilst still allowing the required moves - please excuse the ASCII-art!

 


------------\
----------\  \
           \  \
-----\      \  \
------x------\  \
       \      \  \
--------`------\--`----------
----------------`------------


------------\
----------\  \
           \  \
-----\   /--\--\
------\-/----\  \
              \  \
---------------\--`----------
----------------`------------

 

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