Modern signalling basics for 4 track operation with yard

[bmthtrains - David]

I've been reading up on modern signalling practices (and goodness me that's an endless well to draw from...), including Simon Paley's excellent - if a little too in-depth for the uninitiated - recent publication. Something that I've not seen covered is for 4 track operation. Obviously the principles remain the same, but finding photographs or diagrams is a bit of a challenge. 

 

I'm planning a track layout as shown below, and I've had a go at placing where I think signals should go. Obviously, part of this is down to aesthetic choice and imagination; where signalling blocks start and finish is down to where I want signals to be, and as I want to model a big signalling gantry, there is going to be one!

 

The assumption I am working on is that for a stretch of the modern WCML, all mainlines are signalled for bi-directional working, so the big gantry would be double-faced, signals in either direction. I'm including a small yard and a reception road, and I've put ground signals where it seems appropriate, but I wonder if I've missed anything? 

 

David

 

[Flying Pig]

As far as I can tell (as a total layperson), modern installations seem to keep quite strictly to constant signal spacing, even if this means that a junction is well beyond the signal controlling it.  On that basis would the junction signal you've shown on the up slow be present?

 

Also, given the signalling is bi-directional, would there be an indicator for movements from up slow to down slow over the crossover on the main gantry?

 

[St. Simon]

3 hours ago, bmthtrains - David said:

I've been reading up on modern signalling practices (and goodness me that's an endless well to draw from...), including Simon Paley's excellent - if a little too in-depth for the uninitiated - recent publication. Something that I've not seen covered is for 4 track operation. Obviously the principles remain the same, but finding photographs or diagrams is a bit of a challenge. 

 

I'm planning a track layout as shown below, and I've had a go at placing where I think signals should go. Obviously, part of this is down to aesthetic choice and imagination; where signalling blocks start and finish is down to where I want signals to be, and as I want to model a big signalling gantry, there is going to be one!

 

The assumption I am working on is that for a stretch of the modern WCML, all mainlines are signalled for bi-directional working, so the big gantry would be double-faced, signals in either direction. I'm including a small yard and a reception road, and I've put ground signals where it seems appropriate, but I wonder if I've missed anything? 

 

David

 

Hi David,

 

Firstly thank you for purchasing the book, I know it might be a little too in-depth for some!

 

There’s a few things to change:

 

The Signal on the L/H of your plan with the junction indicator is right or wrong depending on the signalling in the yard.

 

If you keep the ground position light with the RI, then the L/H signal would need a position light instead of a junction indicator. If you change the ground position light with the RI to a Main Aspect Signal (for leaving the yard onto the main line) with position light ( for moves into the next yard), then the L/H signal would be fine.
 

Either way, I would move the signal protecting the R/H reception to main crossover to the left of the points for the siding.

 

Also, depending on the length of your shunt line, then a ground position light might be need to control moves from the shunt onto the reception line.

 

Other than that, I think it’s not too bad (assuming that the R/H edge of your diagram is the physical edge of the scenic section). As Flying pig days, if all

lines are Bi-Directional, the signal on the Up Slow for moves from right to left might need a JI.

 

I hope that makes sense, if it isn’t, I can draw a diagram tomorrow. (I’m writing this on my phone, and can’t draw a diagram).

 

Simon

[bmthtrains - David]

Thanks both, that all makes sense I think. I’ll update the diagram tomorrow and re-post. 

 

David 

[Grovenor]

If its West Coast main Line then I would expect the signals to be 4 aspect.

[Neils WRX]

The signal with the route indicator might actually be some way off the baseboard depending on overlap for the crossover especially if the speed on the slows were say 75mph. This would also have an approach control on it for entering the reception.

 

i would change the shunt signal in the reception to be a main aspect to allow a train to depart towards the left.

 

The other shunt signal in the reception needs to before the points to provide protection for the crossover. You could always just swap this for a main aspect signal.

 

The shunt neck also needs a ground signal to control a loco moving back into the reception road.

 

Hope that helps,

 

Neil

[bmthtrains - David]

I've had another pass at the diagram, as shown below. I've kept the left hand signal even though it probably would be off-board, just for visual interest, and switched the main line signals to 4 aspect. 

 

A couple of issues have now sprung to mind. The signal marked 1 on the plan, now a main aspect with a position light, seems to still lack enough control to indicate which track a departing train would go on - the shunt and up slow seem covered, but what about across the immediate crossing to reach the down slow?

 

Similarly, for signal 2, I have added a route indicator as having moved the signal guarding the crossing back to the up slow on the right hand end before the points to the yard, traffic leaving the two sidings need to be directed either back to the main line or straight on further into the off-scene yard. 

 

I also had a question about TPWS loops on bi-directional lines. Given the gantry signals can be approached for either direction, there would be loops well-off to either side (possibly off board), but at the actual signals, would there be pairs of loops, or would just one be used, approached from both directions?

 

David

[St. Simon]

Hi David,

 

Your plan looks fine.

 

As you say, 1 should have a route indicator on it, which would be a standard route indicator (theatre box).

 

For TPWS, their would be two loops, one for each signal, mounted a few metres on the approach to the signals in the centre of the track. The train will be able to detect which direction each set of loops apply to be sequence in which it detects the arming and trigger frequencies.

 

Simon

[Neils WRX]

That looks fine to me.

 

The only bit I'm now not sure about is the shunt signal on the reception before the crossover, as any train heading out onto the Up Slow would run at a reduced speed until it sighted the next main aspect signal. This would most likely be a main aspect signal.

 

Thanks,

 

Neil

[The Stationmaster]

10 minutes ago, Neils WRX said:

That looks fine to me.

 

The only bit I'm now not sure about is the shunt signal on the reception before the crossover, as any train heading out onto the Up Slow would run at a reduced speed until it sighted the next main aspect signal. This would most likely be a main aspect signal.

 

Thanks,

 

Neil

The decision to provide, or not provide a main aspect depends on all sorts of things so it will vary from location to location and according to the nature of the movements passing the signal.  We spent an undue amount of time in one of the St.Pancras signalling meetings discussing exactly that point in respect of a particular siding and in the end we settled on a 2 aspect (red/yellow)  running signal because the signal would inevitably be cleared while the next signal in advance was still at danger and the line was on a rising gradient.

 

The big problem with using a shunt aspect is not so much running at reduced speed (which obviously happens with a single yellow) but having to run at an even more constrained speed than that prepared to stop at any time before reaching the next running signal.  What decided it for us in that particular case was the rising gradient.

[Neils WRX]

Depending on the layout of the off board yard and any other fixtures (bridges etc) I would be pushing to change it to a main aspect signal, but there are locations around which do use a shunt signal.

 

Thanks,

 

Neil

[bmthtrains - David]

Thanks everyone, I’ll probably make it a main aspect as it would nicely balance the layout even if not strictly necessary. 

 

I may also switch back to three aspect signals as looking at photos of the WCML around Rugby (which this is based on) it seems to use 3 rather than 4.

 

Something I’m learning fast about signalling is that a lot of it is all individual to the site - as it should be, so it’s hard to learn the rules when they’re necessarily so flexible!

 

David

 

 

[Grovenor]

Rugby was all 4 aspect when originally resignalled surely it has not since been reduced to 3?

Note that with modern LED signal heads its not always obvious how many aspects they have.

[bmthtrains - David]

It's rather confusing, that stretch of line seems to have both 4 and 3 aspect signals. Photographs looking north from the platforms clearly show just 3 aspects, but a little further up, gantry signals definitely have 4 further away on open stretches of track. (To clarify, the signals have 3 'heads' then further out 4 - no reason why they can't use 4 aspects I suppose given they are LED, its more to do with what to physically model - 3 heads or 4).

 

I will used my creative eye to see what looks best!

 

David

Edited September 16, 2020 by bmthtrains - David

[Flying Pig]

2 minutes ago, bmthtrains - David said:

It's rather confusing, that stretch of line seems to have both 4 and 3 aspect signals. Photographs looking north from the platforms clearly show just 3 aspects, but a little further up, gantry signals definitely have 4 further away on open stretches of track. 

 

I will used my creative eye to see what looks best!

 

David

 

I'm finding photos like this one which I believe is a four aspect LED type.  Possibly worth looking for a recent cab view video on Youtube.

[bmthtrains - David]

That’s another type then! It’s not the aspects that I need to iron out but the number of heads. Seems to be a real mix of 2, 3 and 4 head signals round there.

 

David 

[Flying Pig]

A couple of useful videos.  The first shows a mixture of incandescent and LED four aspect signals approaching Rugby from around 16 minutes:

 

 

The second shows the signalling on the four track section of the Trent Valley line neat the beginning.  Note that up and down signals are in separate gantries (also signals aren't always close to junctions).  I can't work out what's going on with the bi-directional signalling either!  It all seems to be LED.

 

 

[bmthtrains - David]

Thanks,

 

The videos are really helpful, even if just to show the variety of signalling going on.

 

All the way from Rugby station to Trent valley junction there’s what seem to be long runs of waist height lights all the way along the track and I’m trying to figure out their purpose. 

 

Lots of good lineside details to pick out on the film.

 

David

[St. Simon]

46 minutes ago, bmthtrains - David said:

Thanks,

 

The videos are really helpful, even if just to show the variety of signalling going on.

 

All the way from Rugby station to Trent valley junction there’s what seem to be long runs of waist height lights all the way along the track and I’m trying to figure out their purpose. 

 

Lots of good lineside details to pick out on the film.

 

David

 

Hi David,

 

They will be lighting to be used during the night when possessions are underway or during patrolling, they are usually only found around junctions, but can be found in other strategic places. Originally they were introduced on the WCML, but now being installed at other places, usually when they undertaken an S&C renewal or other major works.

 

Simon

[The Stationmaster]

2 hours ago, Flying Pig said:

 

I'm finding photos like this one which I believe is a four aspect LED type.  Possibly worth looking for a recent cab view video on Youtube.

It's a twin lens, four aspect signal if anybody wisahes to be pedantic.  with the mofdern signal heads a 3 aspect Dorman style LED head a has only one lens. 

[St. Simon]

2 hours ago, bmthtrains - David said:

It's rather confusing, that stretch of line seems to have both 4 and 3 aspect signals. Photographs looking north from the platforms clearly show just 3 aspects, but a little further up, gantry signals definitely have 4 further away on open stretches of track. (To clarify, the signals have 3 'heads' then further out 4 - no reason why they can't use 4 aspects I suppose given they are LED, its more to do with what to physically model - 3 heads or 4).

 

I will used my creative eye to see what looks best!

 

David

 

Hi,

 

I assume that you are talking about the number of apertures that the signal head has, rather than the number of heads a signal has (unless it is 'co-actor', they usually have one)?

 

One type is where you have an aperture for each aspect, these are almost all filament lamp (SL35s), but there are some which are LEDs (mostly from the Signal House Group range).

 

The second type is the 'searchlight' signals which have one aperture for the Red, Single Yellow and Green aspects and then a second aperture for the double yellow aspect (if fitted). There are very few of the filament lamp 'searchlights', while the rest are from Dorman or VMS ranges. Dorman produce three types of LED searchlight, one is a lightweight type for 'standard' signals (which in themselves have two profiles for 3 aspect signals), one is their 'Integrated Lightweight Signal' and one is their 'Colour Light Signal'. The VMS range is just their 'lightweight' type.

 

The LED searchlights are a slight minefield, you can find pictures of all the signal head types in Figures 37, 38 and 39 on pages 43 and 44 of my book.

 

LED signals are now the go to type when a filament signal needs replacement, however, the choice between the types of LED signal is not really defined, it is mainly down either to choice by the signal sighting committee (although rarely to the SSC force a certain make of signal) or whoever, with whatever product, wins the contract for providing the signals for a project. If you go for models of Dorman 'Standard' Searchlights, you can't go far wrong.

 

Simon

[bmthtrains - David]

That makes sense, apertures is the term I was looking for!

 

Just finished watching the video and the other thing that’s noticeable is the sheer variety of OHLE set ups. Annoyingly, the two most common types of register arms and supports aren’t made by N-Brass, they have older WCML types.

 

I may have to design some of my own and get them etched.

 

Simon, have you thought about a follow up book that covers the rest of the line side - those lights, cable troughs, OHLE etc. There’s so much out there (especially the staggeringly OTT Equipment on the GWML electrification...) to keep track of!

 

David

[St. Simon]

13 minutes ago, bmthtrains - David said:

Simon, have you thought about a follow up book that covers the rest of the line side - those lights, cable troughs, OHLE etc. There’s so much out there (especially the staggeringly OTT Equipment on the GWML electrification...) to keep track of!

 

David

Hi David,

 

Yes, as part of a ‘modelling the privatisation era’ book, in fact I might restart that book if there’s enough interest.

 

Simon

[Flying Pig]

In contrast to the other videos and slightly OT, here's a video from 1985.  Rugby is at about 1:02:00 and proposals for bi-directional running on the Trent Valley line are discussed from 1:05:20.

 

 

[bmthtrains - David]

I'll enjoy watching that one too - suddenly found cab ride videos to be oddly soothing after a stressful day!

 

David