How do shunt signals work?

[Tom_N_Gauge]

Hi,

 

Sorry to ask such a open ended question but how do shunt signals work? I know they have a double red for danger and a double white for proceed but where are they placed and how are they used?

 

Are they used to signal only inside a yard, for example in the diagram below protecting sidings 2 and 3. Would you place a limit of shunt (permanent double red) and a two aspect signal at position 1 protecting the exit to the mainline?

 

Thanks,

 

Tom.

Edited May 11, 2018 by Tom_N_Gauge

[Gwiwer]

At position 1 there should be a trap point to prevent runaways escaping onto the main line.  In front of the trap point there should be a position light (in current style) or rotating disc shunt signal.  The disc would normally be of the yellow / black variety with green and yellow lenses.  When the route is set from the yard to the main line and the trap point lies normal the disc rotates to show the green.  Otherwise it sits horizontally and shows yellow.  The junction point at the main line and the trap point would normally co-act and might be set with the same lever.  If using colour-light signalling then the ground position light signal will show two reds horizontally for a stop aspect.  If fitted with incandescent bulbs it will show one red and one white light for proceed with the white inclined at 45 degrees above and beside the red.  If fitted with LEDs it will show two whites at 45 degrees.

 

Positions 2 and 3 do not need to be signalled but this depends upon your local working arrangements.  In many yards the Yardmaster was in charge of all movements and nothing moved without his authority.  He would authorise moves within yard limits in other words as far as your position 1 but no further.   If you wanted to signal each siding then you need the red / white ground discs with red / green lenses though the colour-light version will be the same as above.

 

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.  These boards permitted shunting within station limits and to just beyond.  Current limit of shunt indicators are the permanent double-red ground signals.

 

The recent appearance of permanent double-red ground signals in main line locations is in response to a need to signal when a move cannot be permitted.  For example it may be permitted for a train to enter a station platform in the opposite direction to normal travel but go no farther, such as when a reversal or emergency terminating move is authorised.  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.

[Reorte]

At position 1 there should be a trap point to prevent runaways escaping onto the main line.  In front of the trap point there should be a position light (in current style) or rotating disc shunt signal.  The disc would normally be of the yellow / black variety with green and yellow lenses.  When the route is set from the yard to the main line and the trap point lies normal the disc rotates to show the green.  Otherwise it sits horizontally and shows yellow. 

Why would it be a yellow and not red disc (if it were a disc and not colour lights)? I thought it would only be yellow if there was a headshunt (instead of the trap), so using it would require passing the signal when not cleared on to the main line.

[Gwiwer]

Fair point as the yellow aspect would permit a move ahead through the trap.  As many yards had a kick-back loco road or headshunt doubling as the main line trap and it is the end of a rather long week I may have become confused.  Yes it is a requirement to have a stop aspect to protect the main line.

[PaulRhB]

You would only have a yellow / black dummy with a headshunt, never a trap as the trap is just a derail.

Shunt signals would only control entry and exit to the yard, the shunter controls all other moves within the yard by hand or verbal signals. So either side of point 1 you need a ground signal and that's it.




A limit of shunt board would only be used if the shunt entered a running line against the direction of travel, (i.e. If your point was the other way round), to provide a limit to the shunt move before it stopped and proceeded in the correct direction.

Semaphore discs were replaced very slowly by the original colour light dummies which showed 2 white or 1 red/1white,(edit correction as below!) they were replaced by the 2 red/ 2 white from the 2000's. A few discs still survive at manual boxes but I think all the early colour lights have been upgraded now.

Edited May 12, 2018 by PaulRhB

[E3109]

Gwiwer I hope this doesn't sound picky but you probably need a comma in there, or people could misconstrue with parlous consequences. Thinking more trainee drivers than us toy train folk!

 

As in "one red light and one white light for Proceed".

 

Regards

E3109

[RailWest]

>>>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. 

[PaulRhB]

need to proof read my writing

[Tom_N_Gauge]

Thank you for the responses so far!

 

I've attached a photo and diagram of the layout I'm planning below. it will be a little different when I get started on the baseboard as I'll be using peco code 55. I also won't have the interchange on the mainline, and unfortunately as much as I would like to have one, I don't think there will be space for a trap point.

 

As far as signaling goes I want to be realistic but being such a confined layout not go overboard. A couple of questions for you.

 

• Are signals and speed restriction signs ALWAYS placed on the left/above the line they relate to?
• Would the service line on my layout delivering to the interchange shed be part of the mainline, or considered part of the yard above?

Regarding signaling and what you've all said above I was thinking of having:

 

• A full red/yellow/green signal with single feather at position 1.
• A double red/double white shunt signal at position 2, protecting the service line/mainline.
• A full red/green signal at position 3 protecting the mainline, and a LOS indicator to allow shunting on the service line.
• Ignore position 4.

Your opinions are most welcome.

 

Tom.

Edited May 12, 2018 by Tom_N_Gauge

[big jim]

Without going into the signalling the inner line to me would be part of the power station tracks and the outer line the mainline (which could be a single line)

 

I would also suggest there be another set of points facing the opposite way to allow trains out of the merry go round loop from right to left as well, if you look at the train with the 66 on (despite facing the wrong direction for normal 2 track running) there is no way it can get into the power station without setting back over the points, similarly leaving would involve a set back out of the place

 

If possible I’d also put 2 more loops in the hidden area long enough to accommodate both trains as at some point they will both be on the same line facing opposite ways either wanting to get into or out of the power station so need to pass

 

Ideally you also need another discharge shed for your stone train, I’d say mirroring the other one in the ‘green line’ as they wouldn’t get stone and coal mixed up in the same hopper

Edited May 12, 2018 by big jim

[Coryton]

You would only have a yellow / black dummy with a headshunt, never a trap as the trap is just a derail.

 

Shunt signals would only control entry and exit to the yard, the shunter controls all other moves within the yard by hand or verbal signals. So either side of point 1 you need a ground signal and that's it.

 

IMG_4334.PNG

 

 

A limit of shunt board would only be used if the shunt entered a running line against the direction of travel, (i.e. If your point was the other way round), to provide a limit to the shunt move before it stopped and proceeded in the correct direction.

 

Semaphore discs were replaced very slowly by the original colour light dummies which showed 2 white or 1 red/1white,(edit correction as below!) they were replaced by the 2 red/ 2 white from the 2000's. A few discs still survive at manual boxes but I think all the early colour lights have been upgraded now.

 

Assuming left hand running, don't you need something to stop trains when the points into the yard are set against them?

[PaulRhB]

Assuming left hand running, don't you need something to stop trains when the points into the yard are set against them?

Yes but we were only talking about the shunts The main aspect would be somewhere in rear of the points but not necessarily right by them. It could be a mile away or a few hundred yards.

Equally you'd often have a crossover so the sidings could be accessed by either line but again they could be some distance away.

[Grovenor]

Regarding signaling and what you've all said above I was thinking of having:

• A full red/yellow/green signal with single feather at position 1.
• A double red/double white shunt signal at position 2, protecting the service line/mainline.
• A full red/green signal at position 3 protecting the mainline, and a LOS indicator to allow shunting on the service line.
• Ignore position 4.

Sorry, but I can't see any of these reference numbers on the plan so its rather impractical to comment.

Regards

[Tom_N_Gauge]

Sorry, but I can't see any of these reference numbers on the plan so its rather impractical to comment.

Regards

 

Hi,

 

There is a photo of my layout and a track plan with the numbers on.

 

Tom.

[Tom_N_Gauge]

Hi Big Jim,
 

I would also suggest there be another set of points facing the opposite way to allow trains out of the merry go round loop from right to left as well, if you look at the train with the 66 on (despite facing the wrong direction for normal 2 track running) there is no way it can get into the power station without setting back over the points, similarly leaving would involve a set back out of the place

 
The interchange on the main line isn't going to be there, the tracks will be straight through. I didn't say this above but there will be a full set of interchanges on the other half of the baseboard allowing trains from both directions to change tracks.
 

If possible I’d also put 2 more loops in the hidden area long enough to accommodate both trains as at some point they will both be on the same line facing opposite ways either wanting to get into or out of the power station so need to pass

 
The other side of the baseboard there are going to be mainline interchanges, two sidings, carriage wash, and a maintenance building. I don't have enough Kato Unitrack to do all of it.
 

Ideally you also need another discharge shed for your stone train, I’d say mirroring the other one in the ‘green line’ as they wouldn’t get stone and coal mixed up in the same hopper

The trains running on there are just what I had to hand (I know they're going the wrong way). I have a full rake of GBRF coal hoppers somewhere.

 

I'm not to concerned with the signaling on the main line, I was more interested with getting the signalling inside and leaving the yard correct. With the limited space (180x80) I have not everything is going to be prototypical.

 

Thanks, Tom.

[Tom_N_Gauge]

Hi Paul

 

Yes but we were only talking about the shunts The main aspect would be somewhere in rear of the points but not necessarily right by them. It could be a mile away or a few hundred yards.
Equally you'd often have a crossover so the sidings could be accessed by either line but again they could be some distance away.

 

Yes, you are correct. I'm only concerned with the signaling within or immediately next to the yard.

 

All the mainline signaling and switching is going to be to far down the track for me to model properly and I don't want to overload the layout with signals.

 

The interchange at the bottom won't be there on the final layout. The other half of the layout will contain a junction and sidings.

 

Tom.

[Gwiwer]

 

 

Are signals and speed restriction signs ALWAYS placed on the left/above the line they relate to?

 

Usually yes but there are many exceptions.  Signals are placed where they are required but their exact positioning is determined by local conditions for best sighting and sometimes by historic tradition.

 

As examples the GWR used to have right-hand drive locomotives and placed many signals to the right of both running lines (so not only on the "wrong" side but outside the opposite running line as well) provided that they could be clearly sighted by crews.  It remains quite normal to find signals on the right hand side of a running line if that is the best place for crews to see them.  

[Grovenor]

Hi,

 

There is a photo of my layout and a track plan with the numbers on.

 

Tom.

Sorry, I was looking for numbers on the photo and ignored the sketch.

 

Regarding signaling and what you've all said above I was thinking of having:

• A full red/yellow/green signal with single feather at position 1.
• A double red/double white shunt signal at position 2, protecting the service line/mainline.
• A full red/green signal at position 3 protecting the mainline, and a LOS indicator to allow shunting on the service line.
• Ignore position 4.

At position 1 you would not have a feather as the divergence is into a yard not a running line, the divergence would more likely be controlled by a subsidiary signal with two white lights at 45 degrees under the main aspect.

At position 2 there is no need for anything, but you could have a "stop and await instructions" board to hold trains outside the shed till called forward by a shunter.

At position 3 a red/green signal for departure is OK. No LOS, the red signal does that.

Regards

[E3109]

Indeed.

I once had to take a dmu bang road from Leyland to Preston due to a FUBAR and there are many, many dummies for shunt moves in the Preston 'station limits'.

 

Yes, I signed the road.

No, I didn't have a clue whether otherwise familiar dummies applied to me when working in the wrong direction.

As ever, Preston PSB were superb and advised that I was free to proceed. One of the few boxes I know of, who when questioning a move, didn't use the standard BR response of "You sign the road, driver."

 

What made it worse that this was in thick fog, maybe 6ft visibility at best.

[E3109]

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.

[E3109]

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.

[big jim]

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.

 

Caldew bridge jn?

[big jim]

To be honest Tom you could get away with no signals in the yard itself, ratcliffe has signals controlling movements towards the unloading hoppers, “Toton” signals for unloading and signals to exit the merry go round loop towards the mainline whereas ironbridge power station had nothing at all once you passed the stopboard from the end of the single line

[E3109]

Caldew bridge jn?

Nah mate Salop Goods off the Up WCML Independent on approach to Basford Hall Yard.

Just to add (you probably know this re that location?) he can have you all the way into the yard on subs when following a preceding service, obviously you need to observe them going back and resetting to proceed before taking the sub.

On a sunny day I always ring him, and often even if I've seen it go back and reset.

Pain in the arris for the Siggie no doubt, well if you don't want a call then hold me until you can give me a yeller!

Edited May 12, 2018 by E3109

[big jim]

I once left the north end of Basford hall on the sub with a light engine then realised the signal was for the train in front of me, I’d been given permission to depart by the yard manager and took the signal before spotting the flashing tail light of the previous train that had been hidden behind an OHLE post, I hadn’t seen it go back (as it hadn’t) but having been given verbal permission I thought it was mine

 

Luckily I’d only gone 1/2 a loco past it so was allowed to set back behind it and nothing was said!