How do shunt signals work?

[The Stationmaster]

>>>Semaphore discs were replaced very slowly by the original colour light dummies which showed 2 red or 1 red/1white...

 

No. The original PLSs showed 1 red + 1 white for stop, 2 whites for proceed.

 

>>>A "Limit of Shunt" board or sign was normally placed alongside a main line rather than in a yard.  Its purpose was to define the limit to which a shunting movement was permitted and beyond which full block working would be required.  It could apply to movements into the forward section or to movements back toward the section in the rear.

 

I would disagree in part. Traditionally a LOS board was used on a double-track line to limit movements going in the wrong direction within station limits, for which otherwise there would not have been any stop signal to limit the movement. For movements going in the right direction then you would be limited by the next shunt or main signal or, if shunting into the section ahead, then on the principle that you proceeded only as afar as was necessary to make the shunt. 

 

A Limit of shunt board can quite legitimately be sited outside Station Limits as its sole purpose is to act as a limiting point for shunting movements proceeding in the wroand such movements can be made into a section in rear of a Home Signal (subject to any local restrictions in respect of gradients etc)

 

Incidentally seeing Gwiwer's comment in an earlier post (fixed) double red Limit of shunt signals are exactly that, they are there to mark the limit of movement for a shunting move.  They cannot be used to mark the limiting point of a movement signalled by a running aspect and that must be done by means of a fixed red main aspect although they could be used to mark the limit of a movement signalled by a subsidiary signal but that should not be used for loaded passenger train movements.

[St. Simon]

Under current safety requirements a TPWS grid must be provided to take control of and brake the train if it proceeds too far.  A TPWS grid cannot be provided unless there is a signal for it to act with hence the double-reds.  In some places there is a permanent red main aspect signal fulfilling the same role.  Until TPWS if the train over-ran the permitted limit there was nothing to stop it continuing on the wrong line.  Such an event would be considered a train running away in the wrong direction and with obvious potentially catastrophic consequences.  The permanent double-red ground signal thus has two distinct functions (Limit of Shunt or a stop signal for the wrong direction) but the same meaning namely stop.

 

Hi,

 

TPWS Provision has a lot of myths surrounding it and the most common is that it is provided at all signals. This is false, TPWS provision is only provided for signals that protect a non-rear end conflict. 99% of Shunt Signals are not fitted with TPWS (under exclusion code 'S'), with only Shunt Signals that are either protecting trap points, used for the exit of a depot / yard, or that are limit of shunts being fitted with TPWS. 

 

So whilst you statement of Limit of Shunt Signals are fiitted with TPWS is true, TPWS is not fitted to every shunt signal.

 

There is at least one location I know of, where you can (and sometimes do) get a red aspect with a sub (cat's eyes) and a number 1 flash.

I don't seem to recall this ever being in the Rule Book, although it's legit.

 

Yes, under old standards you can have a Junction Indicator and a Position Light, but not under current standards, any new works must use a Miniature Route Indicator if a route indication is required with a position light, although this could change in the future.

 

Tom (OP)

 

Also bear in mind that a ground signal can be kept 'off' (proceed) for subsequent moves after the first train it was cleared for.

Rule Book etiquette applies (speak to the signalman) but obviously this wouldn't apply on a layout.

In other words, you don't, necessarily, need to replace the GPL/disc to Danger for any subsequent moves.

 

I don't know of any rule that allows a shunt signal to kept off after a move, unless possibly if the opposing locking is omitted, and even then it is very dodgy. As far as I know all signals must be replaced after the passage of each train.

 

Simon

[big jim]

Simon I can think of one location off the Top if my head where a ground position signal can be left off after passage of trains, in fact it was the centre of an alledged spad investigation for us last year, it’s in a recently resignalled area (ROC controlled)

 

Poor old Tom though, bet he wishes he’d not asked the question now!

[St. Simon]

Simon I can think of one location off the Top if my head where a ground position signal can be left off after passage of trains, in fact it was the centre of an alledged spad investigation for us last year, it’s in a recently resignalled area (ROC controlled)

Poor old Tom though, bet he wishes he’d not asked the question now!

Hi Jim,

 

Interesting, as I say I don't know if a rule, but there clearly is one, I'll ask the question when I get in tomorrow.

 

Simon

[The Stationmaster]

Hi Jim,

 

Interesting, as I say I don't know if a rule, but there clearly is one, I'll ask the question when I get in tomorrow.

 

Simon

 

If there is a 'Rule' it is only likely to be in the Signalbox Instructions or a matter of 'local custom and practice, the Rule Book has always required that stop signals (which therefore includes shunt signals) be replaced to danger at a specified time after the movement for which they have been cleared has passed them.  However it was usually the practice to leave both GPLs off where opposing locking is omitted simply to allow work to continue without bothering the Signalman for each movement but it was not included in the Rule Book although that was obviously why it had been specified in to a scheme.

[St. Simon]

If there is a 'Rule' it is only likely to be in the Signalbox Instructions or a matter of 'local custom and practice, the Rule Book has always required that stop signals (which therefore includes shunt signals) be replaced to danger at a specified time after the movement for which they have been cleared has passed them.  However it was usually the practice to leave both GPLs off where opposing locking is omitted simply to allow work to continue without bothering the Signalman for each movement but it was not included in the Rule Book although that was obviously why it had been specified in to a scheme.

 

Yep, a colleague in the office (one you know quite well Mike) has confirmed this, the only thing they can think of is Opposing Locking Omitted (and even that, this is generally only used for trains shuttling back and forth rather than successive trains) or a box / area rule.

 

Simon

[Gwiwer]

By way of examples:

 

Richmond platform 2 (the Up SWR line) has a double red GPL at the country end equipped with TPWS grid. This protects shunt moves between SWR and TfL tracks but platform 2 cannot be used for wrong-direction passenger working as there is no facing point to admit trains from the Down SWR nor from the TfL side. This is shown on track diagrams as a Limit of Shunt mark

 

Kingston platform 2, normally used by Down Shepperton / Strawberry Hill trains, has a full signal aspect showing permanent red at the London (Norbiton) end again in conjuntion with a TPWS grid. This platform is available for Up trains to terminate and reverse back towards Teddington and was used several times each hour for just this purpose during the Waterloo blockade last year. There is also the bay platform but that only holds 8-car trains when 10-car is now the weekday norm. Trains terminating in platform 2 must not be allowed to proceed wrong line towards Norbiton. Daily e.c.s. moves reverse in the platform but loaded passenger moves are also permitted. Approach control is via a subsidiary aspect to signal 410 which also reads to the bay platform. The “full” red is also described on diagrams as a LOS marker but controls loaded passenger trains.

[Steadfast]

I don't know how it is achieved as I'm merely a grease covered bod who bangs trains together not a signal engineer, but certain ground position lights at Westbury can be kept off for multiple moves. Known as a double or a 2 way shunt, the signal in the opposite direction also clears. It is only available with the points directed away from the main lines. This is 702 towards the Salisbury spur (and 705) in the down yard and 711 towards the back Road (and 714) on the up side. If shunting towards the Down Salisbury or Up Reception, only a single shunt, ie one that reverts to danger when back in clear, can be obtained. When finished with the double shunt the signalman has be contacted to put the signal back to danger.

I hope that makes sense with no maps as I'm on my phone

Also, if I remember rightly coming in from the B&H on to the Down Reception you can get a red with a route indication (feather) and a subsidiary signal ("shunt" signal) if there is traffic already on the Reception. It's only a move I've done once or twice in that situation, always light engine and with a driver. Can't remember if the same applies coming from Fairwood

 

Jo

Edited May 22, 2018 by Steadfast

[St. Simon]

I don't know how it is achieved as I'm merely a grease covered bod who bangs trains together, but certain ground position lights at Westbury can be kept off for multiple moves. Known as a double or a 2 way shunt, the signal in the opposite direction also clears. It is only available with the points directed away from the main lines. This is 702 towards the Salisbury spur (and 705) in the down yard and 711 towards the back Road (and 714) on the up side. If shunting towards the Down Salisbury or Up Reception, only a single shunt, ie one that reverts to danger when back in clear, can be obtained. When finished with the double shunt the signalman has be contacted to put the signal back to danger.

I hope that makes sense with no maps as I'm on my phone

Jo

Hi Jo,

 

Yes, that's covered under 'opposing locking omitted', rather than simple shunt being kept off all the time.

 

Simon

[Steadfast]

Ta Simon,

I did presume but it's like another language to me!

 

Jo

[phil-b259]

 

Yes, under old standards you can have a Junction Indicator and a Position Light, but not under current standards, any new works must use a Miniature Route Indicator if a route indication is required with a position light.

 

 

Indeed.

 

Under the 1980s era BML resignalling scheme it was considered perfectly acceptable to use the route indicator provided for use with the main signal aspect (be that a PLJI / 'feather' or a large 'Theatre' type alpha numeric indicator box) with a subsidiary signal where appropriate (e.g. a call on into an occupied platform). For shunt class moves into yards / sidings that were not covered by the main aspect (and which thus could not be displayed by the aforementioned 'feather' or 'Theatre' indicator), small backlit 'stencil' indicators were provided.

 

More recently several of these signals have been replaced at Redhill and the opportunity has been taken to revise the arrangements in the manor you describe (effectively duplication the main signal indicator).

 

To be honest I fail to see any reason for the change in standards - there was nothing wrong with the previous arrangement which minimised on the amount of equipment provided. Not for the first time am I left wondering whether BR would have tolerated such an extravagance........

Edited May 22, 2018 by phil-b259

[PaulRhB]

You don't have to add all the new standards if it's a minor modification of an existing installation that would be different to the other signals. We had exceptions for the route indicators when we scoped returning a platform to passenger use.

The new standards locking do have some interesting effects on previously possible moves

[St. Simon]

To be honest I fail to see any reason for the change in standards - there was nothing wrong with the previous arrangement which minimised on the amount of equipment provided. Not for the first time am I left wondering whether BR would have tolerated such an extravagance........

I personally think that it's better to use a miniature route indicator for a shunt rather than a junction indicator as we can be more descriptive about where you're going rather than simply somewhere over there...

 

Interestingly, the new Rail Industry Standard seems to imply that you can have a junction indicator for a position light, we are still trying to work that out.

You don't have to add all the new standards if it's a minor modification of an existing installation that would be different to the other signals. We had exceptions for the route indicators when we scoped returning a platform to passenger use.

The new standards locking do have some interesting effects on previously possible moves

That sort of thing have come under 'reasonable opportunity' to change the existing arrangement, if you are remodelling the junction, it is reasonable to bring stuff up to current standards, where as if you are just re-opening a platform, it is not necessarily reasonable to upgrade to new standards...

 

Simon

Edited May 24, 2018 by St. Simon

[The Stationmaster]

I don't know how it is achieved as I'm merely a grease covered bod who bangs trains together not a signal engineer, but certain ground position lights at Westbury can be kept off for multiple moves. Known as a double or a 2 way shunt, the signal in the opposite direction also clears. It is only available with the points directed away from the main lines. This is 702 towards the Salisbury spur (and 705) in the down yard and 711 towards the back Road (and 714) on the up side. If shunting towards the Down Salisbury or Up Reception, only a single shunt, ie one that reverts to danger when back in clear, can be obtained. When finished with the double shunt the signalman has be contacted to put the signal back to danger.

I hope that makes sense with no maps as I'm on my phone

Also, if I remember rightly coming in from the B&H on to the Down Reception you can get a red with a route indication (feather) and a subsidiary signal ("shunt" signal) if there is traffic already on the Reception. It's only a move I've done once or twice in that situation, always light engine and with a driver. Can't remember if the same applies coming from Fairwood

 

Jo

 

Opposing locking omitted (as Simon has said) and doing exactly what was specified for them to do - the ones on the Down side originally went in to my spec at the time of the closure of Westbury South.

[E3109]

Just to add. This was before my time really but according to my mate who used to be based at Springs Branch, in the late evening into the wee hours there were a large number of locos coming onto SP and the dummy was kept 'off' religiously.

It was (apparently) a long-standing arrangement between Warrington PSB and the SP ground staff, and kept the WCML from getting snarled up with LE moves.

 

Wind forward to 1996/97 and supposedly, an EWS manager got wind of it and caused a right palaver.

Yes, there wasn't anything in the Local Instructions (or Rule Book) that permitted this.

But it was a long-standing arrangement that nobody had any issue with.

Thanks to Mr Three Beasts sticking his oar in, trains were stacked up as far away as Preston due to the backlog of locos awaiting fuel and servicing.

 

Sometimes 'custom and practice' can be a good thing.

 

I've also heard in the meantime that this issue was pivotal in SP closing as a TMD.

Maybe that was part of the Masterplan.

[LBRJ]

Shunt signals?

 To me that draws to mind images of dark, cold and wet nights, stood on the ballast under the branches of dripping trees, waving ones arms (or a light!) about in the prescribed fashion in the hope that some dude sat quite a way away in a "warm" cab understood what you were instructing to be done. Then stood there waiting for it to be done

 

I suppose they are the sort of every day Ops on the railway, that you really just can't model - well not yet anyways!

Edited May 24, 2018 by LBRJ

[Grovenor]

Just to add. This was before my time really but according to my mate who used to be based at Springs Branch, in the late evening into the wee hours there were a large number of locos coming onto SP and the dummy was kept 'off' religiously.

It was (apparently) a long-standing arrangement between Warrington PSB and the SP ground staff, and kept the WCML from getting snarled up with LE moves.

Where was this dummy and who controlled it?

[beast66606]

Where was this dummy and who controlled it?

 

Springs Branch and Warrington PSB from his description. (SP = Springs Branch, area controlled by Warrington PSB)

[E3109]

I would imagine that by replacing the signal to danger after every move would've caused delay because of the timeout, thus why it was kept 'off' until no longer required.

Having never been on there with a loco or train, I have no idea how long the timeout was set at.

Clearly the loco men would've spoken to the signalman for each individual engine move in any case.

[St. Simon]

I would imagine that by replacing the signal to danger after every move would've caused delay because of the timeout, thus why it was kept 'off' until no longer required.

Having never been on there with a loco or train, I have no idea how long the timeout was set at.

Clearly the loco men would've spoken to the signalman for each individual engine move in any case.

No timeout, or Approach Locking, if the train has taken the route (all colour light signals self replace when a train passes it, unless for the reasons discussed), Approach Locking applies if the train has yet to take the route, and even then the standard Approach Locking timings for a shunt is 30 seconds

 

Simon

Edited May 24, 2018 by St. Simon

[Tom_N_Gauge]

This is the layout so far.

 

Any suggestions on where to put signals would be appreciated. I only want 2-3 to make it loog good.

 

https://imgur.com/a/KzkoQhP

Edited July 18, 2018 by Tom_N_Gauge

[DY444]

To be honest I fail to see any reason for the change in standards - there was nothing wrong with the previous arrangement which minimised on the amount of equipment provided. Not for the first time am I left wondering whether BR would have tolerated such an extravagance........

 

<RANT>

Completely agree and BR would not have done it.  Duplicating route indicators is a waste of money and one of the reasons why everything NR does costs substantially more than it should.  I've heard arguments about separate route indications reinforcing the fact that the set route is permissive and frankly that's nonsense imo.  The signal aspect conveys that information unambiguously.  Any driver that needs the meaning of a signal aspect to be reinforced should be looking for alternative employment.  I expect NR will start providing double reds on running signals without TPWS next to reinforce the fact that the signal is at danger.   

</RANT>

[royaloak]

I've heard arguments about separate route indications reinforcing the fact that the set route is permissive and frankly that's nonsense imo. The signal aspect conveys that information unambiguously. Any driver that needs the meaning of a signal aspect to be reinforced should be looking for alternative employment.

As a current mainline driver I agree 100% with you.

 

There was an incident at my home station where the RAIB went to great pains to blame the signaller for not telling the driver he was going into an occupied platform (no requirement to because that's what the positioning light signal means) and the deficiencies in his training etc (more rubbish) but in no way blamed the driver which is where the blame should have been placed.

Edited July 22, 2018 by royaloak

[St. Simon]

<RANT>

Completely agree and BR would not have done it.  Duplicating route indicators is a waste of money and one of the reasons why everything NR does costs substantially more than it should.  I've heard arguments about separate route indications reinforcing the fact that the set route is permissive and frankly that's nonsense imo.  The signal aspect conveys that information unambiguously.  Any driver that needs the meaning of a signal aspect to be reinforced should be looking for alternative employment.  I expect NR will start providing double reds on running signals without TPWS next to reinforce the fact that the signal is at danger.   

</RANT>

 

Remember it is not NR who changed the standards, it was the RSSB.

 

A miniature route indicator makes more sense to me, one as it provides a consistent approach to position light route indications for both independent position lights and those associated with a main aspect (something which the drivers I have spoken to really want). Secondly (and I think this was the reason for the change) was to prevent a driver mistaking the 'main aspect' route indication used for a permissive move as a main aspect movement authority.

 

Also, there's little change between BR personal and NR personal,  a lot of NR signalling designers are ex-BR guys, so the comment that BR would have done it differently isn't necessarily true,  

 

Simon