Separate post co-acting signals

[Grovenor]

 

What I am not entirely sure about is whether or not they could be passed at danger although I'm inclined to presume that if they could not there wouldn't be so much sense in using a yellow arm

Might also ask what colour glass they had in the on aspect. A yellow would tell you that you had not reached the stop position yet so can pass it.

The more common use of yellow discs/miniature yellows requires the points to be visible to determine the meaning, so you can't apply that rule here.

If its not in the rule book or appendix no-one could complain if a driver pulled past it up to the red arms.

Keith

[big jim]

coming up to date there is a co-acting colour light signal on the single line between crewe and barthomley , the normal LED signal goes out of view for literally 2-3 seconds behind an OHLE stantion so they have put a co-acting LED signal on the ground on the other side of the track, its a fairly recent addition within the lat 3 years or so

[RailWest]

One well-known example (tho' obviously not well enough have been mentioned here yet!) was at Lydford (on the SR lines) in Devon, where the Up Advanced Starting signal had co-acting arms on two separate posts, one to the left of the Up line and the other to the right of the Down line, for sighting purposes because of the curvature of the line.

 

As has been mentioned already, there is a distinction between 'co-acting' and 'repeater' arms. Usually it is easy to determine, because (a) the repeater looks different from the main signal and (b) it is some distance to the rear. But I have come across and instance recently where two 'arms' are marked on a diagram as worked from the same lever, but shown physically to be some (short) distance 'one after the other', yet with nothing to identify the one in rear as being a repeater rather than a co-acting arm. I suspect that in older pre-BR, and certainly pre-Grouping, days the distinction may have been a little more 'fuzzy'.

[Chris Turnbull]

Not strictly related to the OP but people might be interested to know that there was an unusual co-acting signal at Wickham Market Junction on the East Suffolk line.  The branch up home signal was on a sharp curve so the timber post was set at 45 degrees to the track on the "wrong" side, the upper arm being fixed square to the post so that it too was at 45 degrees to the track and could be seen from around the curve.  The lower arm was mounted on a triangular piece of timber fixed to the post such that the arm was at the usual 90 degrees to the track.  There is an excellent photograph of this on page 125 of "The Framlingham Branch" by Peter Paye taken from the top of the signal post looking down.

 

Chris Turnbull 

[DavidBird]

I've just found this page here

http://www.victorianrailways.net/signaling/coact/coact.html

which shows wonderful examples of just what I was asking about!

 

I particularly like the photo of Ballarat Up Home 30, a home splitting 3 ways on the right of the track, co-acting with 30A on the left, almost built-in to the side of the cutting!

 

So, my original question should have been did these occur in the UK (where banner repeaters would be the "normal" situation)?

[seahorse]

Norbury Crossing between Middlewood and Hazel Grove had a standard height signal on the left and a tall signal on the right.

There are pictures in Foxline Scenes from the Past 50 Stockport to Buxton.

[TheSignalEngineer]

coming up to date there is a co-acting colour light signal on the single line between crewe and barthomley , the normal LED signal goes out of view for literally 2-3 seconds behind an OHLE stantion so they have put a co-acting LED signal on the ground on the other side of the track, its a fairly recent addition within the lat 3 years or so

There were quite a few colour lights with co-acters mounted separately. NS148 and NS149 leaving New St South tunnel both had co-acters in the 6 foot because the main signals couldn't be seen from inside the tunnel.. I put in a similar one approaching Kings Cross Thameslink from Kentish Town about 25 years ago which was necessary due to the curvature and not being possible to fit in a banner repeater on the approach.

 

This was NS148 in 1976

Photo C E Steele

[DavidBird]

In the VR examples I linked to above, several of them are distant signals.  In this case as there is not a requirement to stop at the signal, do the two posts still need to be at exactly the same mileage?

 

Norbury Crossing between Middlewood and Hazel Grove had a standard height signal on the left and a tall signal on the right.

There are pictures in Foxline Scenes from the Past 50 Stockport to Buxton.

 

Many thanks, that is just what I was looking for - gives me a UK example to justify including it on my model - and it's even ex-LMS (even if it is LNWR rather than MR)!

http://www.sutherland.davenportstation.org.uk/aaprint/mdl/mdl-59-05.jpg

 

Thanks Seahorse, and all other who have replied.

 

Edit:-

 

In Aug 2009, on Google Streetview here

 

https://www.google.co.uk/maps/@53.365749,-2.093866,3a,75y,60.56h,90t/data=!3m4!1e1!3m2!1sadyr-nymJEsA-pAUvKE4XQ!2e0

 

the "outside" signal (I'm not sure which is Up and Down) has been replaced by a colour-light, and the "inside" is just the short post, no tall post co-acting on the right side of the track.  Has this now been replaced with a banner repeater?

[big jim]

Here we go, the brand new LED co-acting signal berween crewe and alsager, the main signal doesn't "dissapear" behind the ohle when sat in the 2nd mans seat as i discovered this morning

 

[kenw]

Have just come across this topic.

The Stevenage example's an interesting one, though as they're yellow arm and on the approach to the main signal it would appear that they're ( at least functioning as) repeaters rather than co-acting. The top one, in the on position looks to have a yellow lens too.

Wouldn't it also be the case that miniature arm signals wouldn't be used to function as a main stop signal on a main running line? (this is the Fast Line signal). Also, on the Slow Line, where they are genuinely co-acting - on the same post - miniature red arms are used.

Perhaps something of a space / sighting issue with the bridge so close caused this.

 

On a modern theme of the OP, on the ECML there's now several cases where a colour light signal near the exit from a tunnel has the main signal on a bracket with a co-acting ground level signal below.

Remember once being stopped at the preceding signal to one of these (Copenhagen) and asked to report the aspects shown as the previous driver had reported a fault. The bracket signal was at two yellows while it's ground level co-actor was single yellow.

[phil-b259]

Remember once being stopped at the preceding signal to one of these (Copenhagen) and asked to report the aspects shown as the previous driver had reported a fault. The bracket signal was at two yellows while it's ground level co-actor was single yellow.

Not a particularly unusual failure because in 4 aspect territory the top yellow is not lamp proved*. This is because when a double yellow indication is displayed the bottom yellow (also used for the single yellow indication, is lamp proved) will also lit. Thus if the top yellow lamp goes blank although driver will encounter a green, single yellow, single yellow, red sequence, safety is still maintained as the actual distance he has available to stop in remains unchanged from when the top yellow is working correctly.

 

* if red, single yellow or green lamp goes out (or the TPWS fails when the signal is at red) we arrange the signalling system to automatically keep the signal in rear of the defective one at red. If the blank aspect is the red say, then when another aspect becomes lit (e.g. Single yellow) then the signal in rear can change accordingly.

[t-b-g]

North end of Platform 2/3 at Retford!

 

There was a tall signal for sighting above the canopy on the down main line (Platform 2) but when a train was stopped it was impossible for the driver to see so there were two repeaters, each on a separate post, between the tracks of platforms 2 and 3. They read to the main line or to the GCR. These two were miniature arms on individual tubular posts. Originally, the repeater for the main line was a GNR somersault signal just in front of North signal box but that was the far side of a junction to the GCR so it was moved back to be in line with the main signal later.

 

There is also a repeater (Lever 83) for the starter from platform 3 northbound (round the curve to the GCR) that is not only on a separate post, it is around a carriage length ahead of the main signal and (from memory) beyond the down goods line, which crosses on a diamond. Both these were full size arms.

 

Tony

 

Tony

[kenw]

Not a particularly unusual failure because in 4 aspect territory the top yellow is not lamp proved*. 

 

* if red, single yellow or green lamp goes out  we arrange the signalling system to automatically keep the signal in rear of the defective one at red.

 

Yes, and of course I've had plenty of experience of that. What was unusual here, and in relation to this topic, as co-acting heads they were showing single and double yellow aspects together.

Incidentally, although it displays double yellow it's actually a 3-aspect with no green light, the red 'signal' ahead's the buffer stop lamp.

 

* So if the second yellow goes out the signal simply shows single yellow, but if the green goes out the preceding signal's held at red, sorry that's nonsense. If a single yellow or green fail the signal the signal reverts to it's next restrictive aspect, with preceding signals displaying accordingly. If red fails the preceding signal's held at danger.

[Edwin_m]

All the British practice I'm aware of reverts a signal to danger if the next signal is not lamp proved. 

[TheSignalEngineer]

In the 1950s and 1960s on some regions the normal control to feed the yellow aspect of the signal in rear was lamp lit or HR energised. This would allow a Yellow aspect in the event of a lamp failure. To get better than a yellow required lamp lit and HR energised.

[Mike T]

In the 1950s and 1960s on some regions the normal control to feed the yellow aspect of the signal in rear was lamp lit or HR energised. This would allow a Yellow aspect in the event of a lamp failure. To get better than a yellow required lamp lit and HR energised.

This 'lamp or controls' feature that Eric describes above was brought back as the preferred arrangement (probably in the 90's) allowing a form of degraded working although It has again been removed in the latest signalling principle. That said it wasn't often provided in recent years but it is actually being considered for a project at the moment where the signals have limited access so this would help keep things moving under failure.

 

Regards

 

Mike

[Grovenor]

 

This 'lamp or controls' feature that Eric describes above was brought back as the preferred arrangement (probably in the 90's) allowing a form of degraded working although It has again been removed in the latest signalling principle.

Brought back? When was it removed? It was certainly the standard on the LM for the modernisation plan works at least up to Derby in 1969 which was the last one I worked on. 

One would hope that the change to LED signals would make it less valuable, especially if the LED signals are applied throughout a project and can be designed properly instead of emulating filament lamps.

Keith

[Mike T]

Brought back? When was it removed? It was certainly the standard on the LM for the modernisation plan works at least up to Derby in 1969 which was the last one I worked on. 

One would hope that the change to LED signals would make it less valuable, especially if the LED signals are applied throughout a project and can be designed properly instead of emulating filament lamps.

Keith

Hi Keith

 

'Lamp or controls' went out of favour mid late 70's on the LM, I'm sure Eric can confirm a better date than this. All through the 80's and 90's 'lamp' was the favoured proving method. It was reintroduced with GK/RT0060 and GK/GN0706 (might have that number wrong) which morfed in to 11600 but as I said previously rarely applied. I Agee with what you say about LEDs however in certain circumstances especially with low maintenance signals which have limited access every little helps.

 

Regards

 

Mike

[TheSignalEngineer]

At Carlow Street the rules for MAS controls tended to be in the form of memos issued by Jim Fews or Eric Lofthouse rather than the Standard Signalling Principles. I can't remember what was done on Weaver - Carlisle, which followed on from Saltley, Derby and Trent.  

 

Proving of signal lamps was covered by SSP5. This would probably have been first issued in the Woodbridge era.

 

Except for a spell with "The Mod" in 1971 I was involved with design at DS&TEs and RS&TE from 1970 to 1988, and Red Lamp was definitely used for a lot of new work from the mid 1970s. Alterations to an installation usually followed the rules applied at the time it was put in. 

[Mike T]

Hi Eric

 

I am in Crewe on Wednesday and if I think on will see what issues of SSP5 I've got. Failing that I will ask Mr Govey when it changed, just for interest.

 

Regards

 

Mike

[phil-b259]

 

* So if the second yellow goes out the signal simply shows single yellow, but if the green goes out the preceding signal's held at red, sorry that's nonsense. If a single yellow or green fail the signal the signal reverts to it's next restrictive aspect, with preceding signals displaying accordingly. If red fails the preceding signal's held at danger.

 

I can asure you it is not nonsense and am quite happy to provide any number of signalling wiring diagrams  / signalling control tables from the 1980s Brighton line resignalling to prove my point. Even the latest Smartlock computer based signalling installed to control the new layout at Gatwick still obays the same principle.

 

Using the attached track plan exert

 

If a red / single yellow / green lamp goes out in signal T274 for example then T282 signal signal in rear WILL be held at red. This situation will stay the same until T274 signal changes state either through the actions of the signalman or a train clearing the section of track it protects. The interlocking will certainly not turn around and say oh well if we can't get a green on T274 lets try a double yellow instead*.

 

--------------------

 

*Signal control circuits are designed in such a way that they build incrementally, if you want a green aspect then the signal aspect control relays / or SSI module requires the following inputs:-

 

The lamp proving relay for the signal ahead to be energised THEN the control relay for the single yellow aspect to be energised THEN the control relay for the double yellow aspect to be energised THEN the control relay for the green aspect to be energised.

 

With all relays de-energised the signal should be displaying a red aspect. If a lamp should fail in T274 say and the aspect go blank then it has no effect on the control relays - they will remain energised in their relevant positions but the signal will stay blank until the interlocking changes them (to select an alternative aspect) in response to an instruction from the signalman or the passage of a train further along the line triggers the request when the signal is in auto mode. However because T274 is now blank, the signal in rear now has the very first relay of the chain in a de-energised state. It makes absolutely no difference what position the control relays for T282 are in because the signal ahead is not lit it is imposable for any other aspect than red to be displayed.

 

Now let us assume for the moment that T274 was displaying a single yellow aspect when the lamp failed. As per design the signal in rear, T282, will drop from green to red. Now let us assume the signalman spots this and replaces T274 to danger - because the red aspect in T274 is now proved to be lit T282 will change from red to a single yellow. The signalman then has to wait - if he changes T274 signal and the position of trains ahead means T274 would try and show a single or double yellow aspect then all he will do is put T282 signal in rear back to red again as the key condition of having a lamp lit in T274 has not been met (which takes precedence over ALL aspect control relays). If however the signalman is able to get a green aspect on T274 then because that particular lamp is not faulty and the correct control relays are energised T282 signal will also show a green.

 

Now consider what happens if it is the green lamp on T274 that fails. As per the signalling design principles, the signal in rear (T282) goes to red and stays that way until the signalman does something to get a lit aspect back in T274. Lets say that the signalman id fortunate and he happens to have a signal replacement facility further down the line that causes the control relays to instruct T274 to display a double yellow aspect rather than a green aspect. Because the yellow lamp (in the single yellow position) is now proved to be lit, T282 signal in rear will be able to change from Red to Green again.

 

If the second scenario outlined above if the signalman doesn't have a replacement facility - and until the early 90s it wasn't practice to do so in auto sections (that is pieces of track between interlocking where the aspect any signal displays simply relies on the track circuit to which it applies being clear plus the aspect shown on the next signal ahead and said signal aspect being proved to be lit) then the signalman has no choice but to authorise trains past the red signal at caution which plays havoc with the timetable.

 

While obviously replacing the lamp (assuming its simply a case that both filaments inside the actual lamp have failed) is the easiest and usual way of restoring full functionality of the signalling system, in certain situations this may not be possible and the S&T department could be asked to 'restrict' a signal with a defective aspect so that it cannot show a certain aspect. Due to the incremental nature of signalling aspects - you cannot 'skip' one (i.e. you cannot have a four aspect signal able to show red and green but not yellow) but if the control circuitry relating to the green aspect is disconnected then said signal will never show anything more than a double yellow aspect even if the signal ahead shows green.

[Grovenor]

* So if the second yellow goes out the signal simply shows single yellow, but if the green goes out the preceding signal's held at red, sorry that's nonsense. If a single yellow or green fail the signal the signal reverts to it's next restrictive aspect, with preceding signals displaying accordingly. If red fails the preceding signal's held at danger.

I missed this comment the first time around. For the aspect to drop back on lamp failure is a perfectly sensible  arrangement which is more than likely done somewhere, but was not so when I was involved, we just had the lamp or controls condition for the HR. As with quite a lot of things we signal engineers often got stuck in seemingly illogical grooves and getting out of them could be made impossible by the bureaucracy. Why would one go from lamp or controls to lamp always and thereby require a train to be talked past two signals instead of one, or require the signaller to go through mental gymnastics trying to find an aspect that worked? I would suspect someone got disciplined for passing the unlit signal even though the design took into account that that might happen and safety was still assured.

Regards

Keith

[big jim]

i've had a signal drop back on me due to failure of an aspect ahead

 

basically i should have had a minimum of a double yellow at a signal but when i approached it i noticed it was a single yellow which meant i had to get the brake in pretty sharpish as i was doing 75mph at the time with the stobart express with just short of 1200 ton, sure enough the next signal was red when i got there

 

what had happened was the train in front (the caledonian sleeper) while passing through wigan had run over the signalling cable that had been placed over the track by cable thieves and blanked out all the signals behind it, my signals must have been on the next electrical circuit as it were hence why they didnt go out

 

i ended up having to pass 5 signals at danger (ie black) between boars head and springs branch before i picked up lit signals

[big jim]

Passed another location of a modern day version i'd forgot about over the last couple of days, east midlands parkway on both the fast and slow line in the down direction (derby bound) which has co-actors on the platform ends on the opposite line due to the canopy totally blocking the signal, on the slows visibility so bad on the 'normal' signal you dont see it until you have passed over the magnet and are about a loco length from it!

 

Edit: found a pic on wikipedia of the fast line co-actor

 

http://commons.m.wikimedia.org/wiki/File:East_Midlands_Parkway_railway_station_MMB_14.jpg

 

And one of the slow line, that one has a route indicator too, interesting the co-actor is on a tall post and the normal signal is on the ground!!

 

http://www.geograph.org.uk/photo/2561139