Signalling priorities and signal desigm

[billtee]

Now that a very clever modeller has given me a wiring diagram for a three-way point, I can start to design the signals themselves.

 

My 'main line' is the left-hand turnout, so would it be the tallest 'doll' with the centre and right hand tracks both same height (but lower) dolls?

 

I am presuming that 2-colour light signals would be similar to semaphore signals, but don't quote me!

 

Surely there will be someone 'out there' who knows about signals far more than I do, so I await your reply and thank you in advance.

 

Bill

[TheSignalEngineer]

Where and what era are you modelling? Most British colour lights would be a single head with route indicator unless you are going well back in time.

[Edwin_m]

As TheSignalEngineer implies it depends on era. After about 1968 colour light signals had a route indicator for the main route if it was not straight ahead.

[Grovenor]

Bill,

When you asked about the wiring you did not ask for signalling advice, so the wiring provided was to do what you asked.

To use 3 * 2-aspect heads in the format you proposed the colour lights would be direct replacements for semaphore signals and as such the main route would have the tallest doll. This style of signalling, although provided by Eckon, was never particularly common on the prototype. That does not stop you using it of course. In the real world the signals would all show red until a route was pulled off. You would need to add a lever/switch and some more diodes to achieve this.

Regards

Keith

[billtee]

Thank you all for your help in this matter. I have purchased the Eckon 3-way signal which, as advised, is not prototypical. Although a route indicator signal would be more 'correct' and would indicate the right-hand route (lit up) or the straight-ahead route (unlit), how would the main, left-hand route be indicated? I am modelling the present day (era 9), but my layout is purely imaginary as Leamington Spa shed (94D) was demolished and an industrial estate put in its place. My track layout depicts a TMD off a single main line which passes nearby ( and which one day may loop around into a circuit, purely so I can see trains running past.

Bill

[billtee]

I should have added that I am aware that points are normally trailing off a main line, not leading, but space considerations precluded this 'proper' layout. I am assuming that the real double track main line is 'off-scene' and that my main line is the main track into the TMD (right), to the fuelling depot (ahead), and to the carriage sheds and back to the double main line (left). The signals were going to mounted on an overhead gantry, but I've gone off that idea now.

With my excellent wiring diagram, at least I can show the route for my (no doubt confused) scale diesel locomotive drivers. The model points for the main line of my layout will be 'power-operated' with appropriate castings placed by the tie-rods, but all the pointwork within the TMD will be hand-operated via white-handled levers (which I have yet to purchase). In reality all my points are operated by under-board slow-action 12V motors selected by switches on a mimic board.

The layout is DCC, but I didn't want to operate my points using DCC because I would never remember the address of each one!

All my locomotives have sound, which I think really brings them to life!

Bill

[Edwin_m]

Thank you all for your help in this matter. I have purchased the Eckon 3-way signal which, as advised, is not prototypical. Although a route indicator signal would be more 'correct' and would indicate the right-hand route (lit up) or the straight-ahead route (unlit), how would the main, left-hand route be indicated?

 

You would need a signal with two route indicators in a configuration that looks a bit like rabbit ears. These are reasonably common on the prototype but I don't think they are available "ready to run".

 

Don't worry too much about facing points. This was more of a concern in earlier years, and more by some companies than others, but had virtually gone by the colour light era when the necessary facing point locks were provided as standard in point machines even if the points were only trailing.

 

Hand points within the depot is largely correct. However if there is a point in the depot that would divert any runaway moves to prevent them going onto the main line then this would be power-worked simultaneously with the point on the main line that controls access into the depot. If the depot layout has no such point then you need a power-worked trap point to derail any such runaways.

 

As you say a multi-head signal is not authentic for the modern day - a few have been re-introduced recently as "splitting distants" but not relevant to this situation. I can't imagine there are any traditional multi-head colour light junction signals left, but if so I can't say when they disappeared.

[RailWest]

"You would need a signal with two route indicators in a configuration that looks a bit like rabbit ears...."

 

I'm not sure about that. As I read the original question, the main route is the left-most of three. In that case the signal should have two Junction Indicators (NOT Route Indicators, which are different things) both to the right of the head, one at 45-degrees and one at 90-degrees. Alternatively, if we are talking about a depot exit or similar, then a single head with ONE Route Indicator, which would show the appropriate routes.

[TheSignalEngineer]

A sketch of the layout and brief scenario would help to get the best answers. Everyone seems to be shooting in the dark at the moment, unless they have spotted some information that i haven't.

[Edwin_m]

"You would need a signal with two route indicators in a configuration that looks a bit like rabbit ears...."

 

I'm not sure about that. As I read the original question, the main route is the left-most of three. In that case the signal should have two Junction Indicators (NOT Route Indicators, which are different things) both to the right of the head, one at 45-degrees and one at 90-degrees. Alternatively, if we are talking about a depot exit or similar, then a single head with ONE Route Indicator, which would show the appropriate routes.

 

Sorry I was referring to junction indicators aka "feathers". Thinking about this further yes I think you'd need two to the right and one to the left as well.

[RailWest]

Why the lefthand JI ? I thought there was only a total of 3 routes from the signal? A plan would certainly be useful !!

[Edwin_m]

Following the Foxhall Junction accident in the late 60s, if the "straight on" route is not the main route then the main route has a route indicator (we're still talking feathers here!). I think (but I'm not sure) this means the straight ahead route needs one as well.

 

Anyway, all this may be irrelevant because if the routes lead into yards or depots without another signal in between, then they should have subsidiary aspects rather than a main aspect. So I now think the right arrangement would be a signal with one left hand indicator for the main line and a subsidiary aspect, possibly with stencil indicators, for the depot and yards.

[The Stationmaster]

Following the Foxhall Junction accident in the late 60s, if the "straight on" route is not the main route then the main route has a route indicator (we're still talking feathers here!). I think (but I'm not sure) this means the straight ahead route needs one as well.

I've an idea the 'quick fix' approach adopted after Foxhall and the episode at R180 was further refined in the early/mid 1980s. Certainy the situation as I remember reflected in what amounted to a 'signalling facilities' sketch done to clean up my back of a piece of scrap paper initial proposal for Worcester in 1984 was based, so i was told, on some new Instructions. These meant that if the 'straight ahead' rail route was not a signalled route then a JI had to be provided even if it was for the only route in advance of the signal - thus the signal would have a JI if it had one routes but would still have exactly the same form if it had two routes.

 

In the example under discussion i think we are talking about something slightly different - but a sketch would be a great help.

Anyway, all this may be irrelevant because if the routes lead into yards or depots without another signal in between, then they should have subsidiary aspects rather than a main aspect. So I now think the right arrangement would be a signal with one left hand indicator for the main line and a subsidiary aspect, possibly with stencil indicators, for the depot and yards.

Unless the signal reads to a fixed red a sub aspect has to be used and I think it still insists on that in the modern equivalent of the SPs - SE will no doubt confirm or put me right on that. This is one reason why a lot of fixed reds began to appear on schemes from the late 1980s/early '90s onwards when we were looking for higher exit speeds for freights leaving passenger lines and faster connections were only of any value if they were signalled by a running aspect. Thus the Southall area has more than a few fixed reds - which I kept on injecting into scheme specs when we were reviewing layout changes and signalling specs in readiness for Heathrow and other associated changes.

[TheSignalEngineer]

I've an idea the 'quick fix' approach adopted after Foxhall and the episode at R180 was further refined in the early/mid 1980s. Certainy the situation as I remember reflected in what amounted to a 'signalling facilities' sketch done to clean up my back of a piece of scrap paper initial proposal for Worcester in 1984 was based, so i was told, on some new Instructions. These meant that if the 'straight ahead' rail route was not a signalled route then a JI had to be provided even if it was for the only route in advance of the signal - thus the signal would have a JI if it had one routes but would still have exactly the same form if it had two routes. In the example under discussion i think we are talking about something slightly different - but a sketch would be a great help. Unless the signal reads to a fixed red a sub aspect has to be used and I think it still insists on that in the modern equivalent of the SPs - SE will no doubt confirm or put me right on that. This is one reason why a lot of fixed reds began to appear on schemes from the late 1980s/early '90s onwards when we were looking for higher exit speeds for freights leaving passenger lines and faster connections were only of any value if they were signalled by a running aspect. Thus the Southall area has more than a few fixed reds - which I kept on injecting into scheme specs when we were reviewing layout changes and signalling specs in readiness for Heathrow and other associated changes.

 

i) Standard Signalling Principle 6 covered Junction Signalling. It had many incarnations, the first issued possibly even as far back as when Mr Woodbridge was still CS&TE at the Kremlin. The indication of a route when it was the only one from a signal, e.g. the end of bi-directional signalling was definitely in vogue by the early 1980s, as I did a project with some for the NE-SW route improvements after HSTs were introduced on that line, definitely commissioned by 1983. (My memory calendar if referenced by reorganisations so I am clear on that date)

 

Nowadays it would be covered by Part 5 of GK/RT 0045 (Issued 2010)

 

ii) Many Reception roads and loops didn't have track circuiting under early MAS schemes, as there were a lot of instances of old boxes used as Shunt Frames to control the moves once off the main line. Also, exit signals were often only a Shunt signal, so there was no main signal to read up to. The only aspect available for use in these situations would be a shunt, giving the driver authority to proceed on sight to the next signal, a hand signal or an obstruction.

 

Later, Fixed Reds were used in the way that SM says. In addition, they were installed at places like Brent Sidings at Willesden following shunting incidents where a move over-ran a PLGS and came into contact with a conflicting move already in progress.

 

The answer, as with most signalling questions, depends on date and place.

[billtee]

Sorry I haven't been able to participate in the discussion, lads, but things here have been a bit hectic since I returned home from two weeks of caravanning.

I'll try to take a photo of the appropriate board tomorrow so you can see the track layout.

In the meantime, late last night I made up the 2-aspect, 3-way signal by Eckon, but made the left hand doll the highest, the centre doll the next highest and the right head the lowest, because the left hand 'fork' is the 'main line', the straight ahead track is a secondary line past the TMD via the refuelling road, and the right hamd fork leads through a double slip into the TMD itself.

All the points on the main line will be 'power operated' by an off-scene (at the moment) signal box, but all other points, possibly excluding the double slip, will have manual levers.

I have seen a photo on the internet of a three-way point signal where the AHEAD route is the main line, and with feathers angled left and right at 45 degrees for left and right roads, but my layout isn't quite the same as that, damn!!

All the best from a rookie track designer (after all, it's my layout and strictly out of my head with no prototype to base the model upon), and I am definitely not a signal engineer!),

Bill

[billtee]

Here are the promised photos, a bit rushed I'm afraid, and the first photo (Image 002, with captions roughly drawn upon it) shows the three way point and its position shown by a red dot.

The second photo (image 003) shows the board which connects to the first board described above.

Hope this helps,

Bill

[The Stationmaster]

Here are the promised photos, a bit rushed I'm afraid, and the first photo (Image 002, with captions roughly drawn upon it) shows the three way point and its position shown by a red dot.

The second photo (image 003) shows the board which connects to the first board described above.

Hope this helps,

Bill

Bill,

 

If you want to do it an 'old-fashioned' way in terms of colour light signals then what you have done is quite acceptable apart from the fact that you are using two aspect signal heads. (And by 'old-fashioned' I think the last occasion in British signalling new works when splitting heads were used at a divergence was on the GE lines in the very late 1940s/very early 1950s - but they were multiple aspect signals.) For more modern practice - and indeed reflective of what was becoming the 'usual method' from the mid/late 1930s onwards junction indicators would be use - in your case of two to the right of the running signal head one pointing upwards at 45 degrees (Position 4) and one pointing right at 90 degrees (Position 5).

 

However in your case at least one route goes to sidings (and possibly a second one does too?) and they should not therefore be signalled by running signals but should be signalled by a position light subsidiary signals (the thing lit up with two white lights in the pic below of NN35 (but ignore all the other bits & bobs on that signal please. There would probably also be an indication of route with the sub but the way in which that was shown would depend on the Region and era which you are modelling.

 

oops, forgot the pic - here you go

 

So where now. Well in purely technical terms what you have installed on your layout is not correct in several respects - but you have got the signal heads correctly arranged for priority of routes. If you are happy with what you've got then stay with it safe in the knowledge that you might one day wish to change/improve it to something more prototypical; if you want something more protypical then further advice will be forthcoming from several of us once we know Region/era. The choice is yours (but if you intend to exhibit your railway be prepared for someone who might say 'that's wrong'.