yellow arm shunting signal on running line

[ColHut]

I was perusing some track plans looking for examples of cases where there might be two yellow arm shunting signals leading from sidings to running lines through slips.

 

Instead I came across this example of a yellow arm shunting signal on the mainline. A signal that probably allows trains to back over it and is cleared only for a backing move into the spur sidings. It is No.6 signal on this plan of Letchworth on the ex GNR from John Hinson's excellent site. Signals 23 and 30 seem to have similar roles. i had not previously been aware of their use on running lines.

 

http://www.signalbox.org/diagrams.php?id=1061

 

Is my interpretation correct?

 

regards

[The Johnster]

I have probably misunderstood the question, and GNR practice may be different to the GW method of doing things that I am familiar with, but AFAIK, a shunting signal, by which in this case I mean a ground disk or small arm, or ground position light in a more modern environment, clears a route from the road to and in the direction which it applies, as far as the route is clear or to the next fixed signal. The majority of these have red bars across their discs or red small arms and red or green lights at night, or in the case of GPLs show 2 reds for on and 2 diagonal whites for off.  These apply to one route only, and if more than one route is accessible from that position, are stacked one above the other to be read top to bottom = left to right.  It must not be passed at danger.  A yellow bar, small arm. or 2 yellow lights is different in that it may be passed at danger in the direction to which they do not apply, needing to be cleared in the off position to be passed in the direction to which they do apply.

 

A typical location for such a yellow shunting signal to be found would be at the exit of a goods yard, where the off position would apply to the route out of the yard on to a running line, but the signal may be passed at danger in the direction to which it does not apply which is the headshunt of the yard; otherwise the signalman, who has other things to worry about, would have to clear the shunting signal for every move that passed it up the headshunt!  No 4 and no 16 are in such positions on the Letchworth plan, and 4 is marked with a 'y'; assuming that means yellow, it is also applied to nos 6, 23, and 30, and it looks as if the 'direction to which they do not apply', which can be taken by passing them in the on, danger. position, is a wrong line movement towards Baldock (I do not know which is up and which is down here ) on the road coming from Baldock.  It does not make sense to me and it may be that 'y' does not mean yellow on this diagram.

 

I am not aware of any such yellow shunting signals used for backing or any movements across or along running lines in the wrong direction, but as I say GNR practice may have been different and my knowledge of such matters is more at a working knowledge level and I am not to be taken as any sort of authoritative source on such matters; I was a freight guard, not a signalman.

 

Hope this helps, and, if it doesn't and causes confusion, that it provokes a better response from someone more expert in such matters than I am!

[ColHut]

I am intrigued too. I can only guess they allow backing movements along the line past them when 'on' and when off the way has been set on the diverging route. The diagram is dated 1960 and I do not know what modernisation had occured since GNR days.

 

As you say, 'Y' may not be yellow, but this seems unlikely.

 

regards

[micknich2003]

 The attached ex LMS of c1930 may be of some use, the other railways principles would be little different. To best of my knowledge "Yellow" signals for shunting originated c1928, though I'm open to being proved wrong. Likewise, I seem to recall reading the Western did not use Yellow discs until post nationalasation. The "Station Master" I'm sure will keep us all straight.

 

[beast66606]

I'm making an (un?) educated guess here (as ColHut says)

 

The signals concerned would be cleared for the routes over the crossovers BUT there are other routes available from them, 23 could read to 6, 6 could read to 30 and in turn 30 could read to 33 - I assume all of these shunts would be made without clearing the signal however it would need the signalman to show a flag from the box to allow movement rather than the more usual meaning for yellow shunts which is the driver can pass it without permission for routes to which it doesn't apply - in these cases the driver is passing the signal for routes to which it is not cleared but only with authority.

4 is a more conventional use of a yellow arm and 16 isn't marked as yellow although I would expect it to be a yellow arm.

[meil]

Surly 23, 6 and 30 are yellow to permit access to the Garden(?) siding through 33. Permitting the shunting move into the siding without having to pull 23, 6 and 33 OFF.

[Grovenor]

Normally such wrong road moves by shunts would use red arms and would be released by 33 off with the points set for the siding, using yellow arms like that means there is no interlocking stopping signals being cleared in the normal direction and puts all of the onus on the human factors.

Regards

[beast66606]

Surly 23, 6 and 30 are yellow to permit access to the Garden(?) siding through 33. Permitting the shunting move into the siding without having to pull 23, 6 and 33 OFF.

 

33 at least would be reversed but assuming that was a typo and you meant 30 you have repeated what I said

[beast66606]

Normally such wrong road moves by shunts would use red arms and would be released by 33 off with the points set for the siding, using yellow arms like that means there is no interlocking stopping signals being cleared in the normal direction and puts all of the onus on the human factors.

Regards

 

Normally being the key, human factors were not uncommon, plenty of unsignalled shunt moves requiring a wave from the box at lots of places - thats what lever collars were (also) for

[The Johnster]

Handsignalled shunt moves were normally only made in fairly exceptional circumstances, and after the signalman, driver, and anyone else involved had come to a clear understanding of what was about to happen, and for any booked movement a shunting signal with a specific purpose that drivers and guards had to be aware of as part of their route knowledge would be provided.

 

Lever collars were to remind signalmen that a section was blocked and prevented him from accepting other traffic onto it where track circuit interlocking had not already prevented this, and their use was more connected with the acceptance of trains into the station limits from the preceeding box while the line was blocked; the report into the Quintinshill disaster, which was the result of such an acceptance, notes that it would have been prevented by the use of collars, which were not a requirement on the Caledonian in 1915.  The box's interlocking should prevent conflicting movements for shunting moves.                         

[beast66606]

Handsignalled shunt moves were normally only made in fairly exceptional circumstances, and after the signalman, driver, and anyone else involved had come to a clear understanding of what was about to happen, and for any booked movement a shunting signal with a specific purpose that drivers and guards had to be aware of as part of their route knowledge would be provided.

 

Lever collars were to remind signalmen that a section was blocked and prevented him from accepting other traffic onto it where track circuit interlocking had not already prevented this, and their use was more connected with the acceptance of trains into the station limits from the preceeding box while the line was blocked; the report into the Quintinshill disaster, which was the result of such an acceptance, notes that it would have been prevented by the use of collars, which were not a requirement on the Caledonian in 1915.  The box's interlocking should prevent conflicting movements for shunting moves.                         

 

Handsignalled shunt moves were made whenever there wasn't a signalled move - a wave from the box was enough (but not a green flag unless you could lock all the points), booked movements are really a modern invention, it's not that long ago when the local staff decided what happened. At Port Sunlight Sidings the daily (M-F) trip would often leave vehicles on the running line and there was no signalled move to get back onto them, a wave from the box was enough.

 

Lever collars are used to remind signalmen that vehicles are standing on the line in the way of a train which may be signalled onto them, not specifically to do with block instruments although if those vehicles impeded the acceptance point then a blocking back inside home signal should be sent.

Quintinshill is irrelevant to this.

 

Interlocking does not have to prevent conflicting shunt moves, there's such as thing as opposing locking relaxed which allows two opposing shunts to be cleared.

[The Stationmaster]

Very interesting and not something I've come across before although there are one or two oddities in an ER Office Instruction I happen to have a copy of somewhere (Operating Dept Instruction - not S&T).  The signals do in fact strictly comply with the meaning of the Rule but their use in this sort of situation is rather unusual (and in my view incorrect) and I suspect that 'somebody' got things wrong in an interpretation and thus misused the strict meaning of the Rule  - and in that respect it would not be alone on what was or had been the Southern Division of the LNER.

 

Peculiarly the yellow arms have been used in precisely the same way the GWR used white light ground discs so I'm inclined to suspect (and someone might know the answer) that it happened at Letchworth for the same basic reason but that does depend on the interlocking.  The GWR introduced white light independent ground signals around the very late 1880s/early '90 and the reason was simple - the interlocking did not allow for the points to release the signal from either position or for the signal to lock the points both ways.  Thus in GWR practice with pre-tappet locking the signal was only released with the relevant points reverse and had to be passed at danger with the points standing normal - hence the use of a white light instead of a red.  But - exactly as is the situation in the Letchworth example - a white light disc, or succession of them, always led to one with a red light - No.33 at Letchwoth.

 

So I conclude that the interlocking design meant that the ground discs with yellow arms were only released by the points being reversed so some bright spark thought 'ah, no need to spend money bringing the locking up to date - we'll use those yellow discs because the Rule Book says we can'.  The alternative of course would be that shunt back towards Garden City Siding would otherwise have to pass at danger as many as three ground signals all showing red lights.

 

So not a strict application of the usage of a yellow arm ground disc but, I'm reasonably sure, thought up by someone as a way round the problem and duly accepted as such by anyone who happened to notice or they were told to come up with batter answer that didn't cost any more and they couldn't.

 

Was it dangerous?  Interesting question but I've never heard of an instance on the GWR/WR where it led to any sort of collision due to running signals not being locked at danger.  And equally I have never come across (or issued) an Instruction/ Signalbox Special Instruction  which said the red light signal had to be cleared before a movement could be made in the wrong direction towards  in turn suggesting that over the years umpteen setting back movements might have occurred where running signals for a  movement in the right direction weren't locked at danger.  Even as late as the mid 1970s numerous moves were being made past ground signals which were at danger over routes for which the signal could not be cleared (and I know that because we had to do a survey of such moves c.1976 - following a derailment somewhere which had sort of reminded those in ivory towers that such things went on in the real world beyond their office walls).  

 

Even that late (and of course much later) there were things having to take place on the railway where, as 'Beast' so aptly put it ... "(Normally being the key,) human factors were not uncommon, plenty of unsignalled shunt moves requiring a wave from the box at lots of places - ..."  Quite right - at one of my 'boxes in 1976 we were making as many as 40 unsignalled (by means of fixed signals) movements every week day, week after week, month after month etc; and no one was prepared to spend the money on the necessary locking alteration. 

 

Incidentally anyone who has attended one of the RMweb days at Didcot  and who listened to/endured my signalbox 'chat' will know GWR lever collars also had another, very important, use.

[LNERGE]

Funnily enough that is a diagram i can muster....

 

[beast66606]

Funnily enough that is a diagram i can muster....

 

Letchworth.JPG

 

I notice that 32 is also yellow on that diagram which supports mine - and Mikes (SM) - theory about them as 32 can either read via 31s or along the main to 18.

[LNERGE]

I should be able to dig out the locking table, dog chart and pull plates drawings if required.

[beast66606]

I should be able to dig out the locking table, dog chart and pull plates drawings if required.

 

Would be nice to see if you can please.

[ColHut]

The locking chart would be great indeed. Do you have a date for that chart?

 

 

If 32 was not cleared for movements back along the down main, then such movements would presumably stop at the red disc no.8 unless otherwise directed.

[ColHut]

Just one other interesting thing. The shunting signal 10 is perhaps placed just passed the toe of the point, but he points themselves are handworked. Was this common?

 

regards

[beast66606]

Just one other interesting thing. The shunting signal 10 is perhaps placed just passed the toe of the point, but he points themselves are handworked. Was this common?

 

regards

 

In yards yes - and sometimes the juxtaposition shown on the diagram is wrong - it's showing that 10 refers to both roads but the setting of the point is" on the ground."

[TheSignalEngineer]

Just one other interesting thing. The shunting signal 10 is perhaps placed just passed the toe of the point, but he points themselves are handworked. Was this common?

 

regards

 

Yes, the signal was at clearance from the Reception Line but the first hand points in the sidings were foul.

[LNERGE]

It'll be this evening before i can go looking for the documents mentioned. Domestic duties I'm afraid. I'm about to have a couple of days away to play with a level crossing and it's protecting signals so i'd better do as i'm told if only for a while.

[LNERGE]

I have found the Letchworth file at least. A quick glance shows 32 needs 14. Why is it yellow?

[beast66606]

I have found the Letchworth file at least. A quick glance shows 32 needs 14. Why is it yellow?

 

Indeed - and why does it need 14 when 6 is in the way ! - could be a drawing error on the actual box diagram.

[LNERGE]

This is revision C. My paperwork goes up the revision G, TCB to Hitchin panel. The data panel from the Layout and Linewires has a few dates on it when changes occurred.

 

 

 

 

 

 

[The Stationmaster]

So presumably the discs were altered to red arm with the 1968 re-locking and 'signal renewals'?