SIGNALLING WITH COLOUR LIGHTS

[shibushe]

I am getting to the point on my layout where signalling needs to be planned.

The method. I will be using train-tech automatic signals.

 

So, not being familiar with modern signalling I need some help.

Home, Distant, not sure what this means and how that is relevant.

 

My local stations main lines seem to have 4 Aspect at least those I can see.

Slow lines are 2 Aspect.

Should then I install all 4 Aspects on the main, and 2 Aspects on the slow.

Await replies with much interest.

[TheSignalEngineer]

It would help to put up a sketch of the track layout and tell us the location and era as this will

determine what is needed.

If you can do that I'm sure that we can come up with some suggestions.

[shibushe]

It would help to put up a sketch of the track layout and tell us the location and era as this will

determine what is needed.

If you can do that I'm sure that we can come up with some suggestions.

HI. Not able to supply a sketch. But if you can imagine 4 tracks 2 are up & down mains.  The other two are slow passenger/ freight.

Image is Modern, Steam Specials when I feel like a change.

As I said in my post my local lines as far as I can see are 4 aspects on the mains.

Two aspects on the slows, at least those that I can see.

I will be on the platform in the dark tomorrow morning so will check again, sure I am right.

[njee20]

As is being alluded to, it depends.

 

Would be quite unusual to only have 2 aspect signals on the slow lines, although I'm sure there are examples, such as wherever you are. You limit your capacity and running speed very markedly like that though, which is unusual in a location where 4 running lines have been deemed necessary. Far more common would be at least 3 aspect signals on the slow lines as well, if not 4 aspects on all running lines.

 

Home and distant aren't really relevant for colour light signals, they are by their very nature combined home and distant, with the possible exception of some 2 aspect signals, where you can obviously only have two out of red/yellow/green. The same signal showing yellow is a distant signal, or a home if it's showing red.

 

So, as with all of these things, it's up to you. If you don't have a specific prototype you can do what you want. I'd personally go for 4 aspect on all running lines, or 3 on the slow lines if you want a difference.

[TheSignalEngineer]

Where is the local line you are referring to? I know of a few cases where two-aspect signals were provided on Goods lines in a four-track location but that was for special operating circumstances. Don't forget that some three and four aspect heads have been changed for LED heads which can show more than one colour from each lens.

If three and four aspect heads were provided for adjacent lines it would be because of a large difference in permitted speed, but mixing is undesirable as it can lead to confusion by drivers.

Whatever is provided it is best to have signals parallel on each line in a particular direction as this cuts down the chance of mid-reading.

[phil-b259]

If three and four aspect heads were provided for adjacent lines it would be because of a large difference in permitted speed, but mixing is undesirable as it can lead to confusion by drivers.

 

The ECML heading north from Welwyn being one such example - the braking distances on the slow from a single yellow to the red being sufficient at 100mph but not at 125mph so the fast lines have 4 aspect heads fitted.

[njee20]

Yes, the ECML was the example I was thinking of with 3 aspect on the slow lines.

 

All others that I immediately think of are 4 on all running lines I think.

[The Stationmaster]

Where is the local line you are referring to? I know of a few cases where two-aspect signals were provided on Goods lines in a four-track location but that was for special operating circumstances. Don't forget that some three and four aspect heads have been changed for LED heads which can show more than one colour from each lens.

If three and four aspect heads were provided for adjacent lines it would be because of a large difference in permitted speed, but mixing is undesirable as it can lead to confusion by drivers.

Whatever is provided it is best to have signals parallel on each line in a particular direction as this cuts down the chance of mid-reading.

 

There were a few locations on the GWML where the early-mid 1960s resignalling work used 3 aspect signals on the Reliefs and 4 aspect on the Mains (and mixed successive 3 & 4 aspect on the Reliefs in a few places - ugh!!!) and that was all down to line speed differences.  A lot of the resignalling west of Swindon (basically to Bathampton and Westerleigh and mainly west of Wootton Bassett) used 2 aspect signalling as even continuous 3 aspect wasn't justified but that all went when line speeds were raised for HSTs.  The last lot of continuous 2 aspect - which might still survive? - was between Bathampton and Bradford Jcns and there was also some on the Western Valley.

[AberdeenBill]

There were a few locations on the GWML where the early-mid 1960s resignalling work used 3 aspect signals on the Reliefs and 4 aspect on the Mains (and mixed successive 3 & 4 aspect on the Reliefs in a few places - ugh!!!) and that was all down to line speed differences.  A lot of the resignalling west of Swindon (basically to Bathampton and Westerleigh and mainly west of Wootton Bassett) used 2 aspect signalling as even continuous 3 aspect wasn't justified but that all went when line speeds were raised for HSTs.  The last lot of continuous 2 aspect - which might still survive? - was between Bathampton and Bradford Jcns and there was also some on the Western Valley.

 

Are the continuous 2 aspect signals alternating 'distant' (yellow/green) and stop (red/green)?     This model was used in the New Forest in 1967 for the Bournemouth electrification, but later upgraded to 3-aspect. 

 

Thanks,

Bill

[TheSignalEngineer]

Aynho to Wolvercote was done as 2-aspect Distants and Homes c1968.
There were some sections on the Midland lines Saltley, Derby and Trent scheme at the same time done with 4-aspect on the Main/Fast lines and 3-aspect on the adjacent Slow/Goods lines.

[Lancs_fus]

Given shibushe's original post and that we don't seem to be able to see a sketch nor does the original post indicate it needs to be particularly prototypical, isn't this a case of whatever feels kind of right rather than what is exactly like something in existance? I think a fit for purpose approach of multi aspect mains and dual aspect secondaries may well fulfill the OPs original desire without anchoring it in prototype but happy to be deemed incorrect if I have misinterpreted the original question.

[The Stationmaster]

Are the continuous 2 aspect signals alternating 'distant' (yellow/green) and stop (red/green)?     This model was used in the New Forest in 1967 for the Bournemouth electrification, but later upgraded to 3-aspect. 

 

Thanks,

Bill

 

Yes, (and thanks to SE for reminding me about Aynho - Wolvercote).  On some of the WR schemes the 2 aspect installations effectively created about the same number of sections that had previously existed although some were considerably fewer in number than the number which had existed in the semaphore age about 10 years previously - it was all about money and traffic expectations.

[shibushe]

Thanks for all the replies folks. Spotting how the signals are arranged is difficult on my local station, its on a curve, in the dark even with my face against the glass I cant see them only at red.

I think reading your replies I may as well signal the layout thus. 4 aspect on the mains, 3 aspect on the slows.

No ones going to see it may not be prototypical but then again it is my layout. Auto changing signals will just add that bit of fun.

 

Now I have another question. What is the purpose of a signal that has a Feather and where would such a signal be placed.

[TheSignalEngineer]

Now I have another question. What is the purpose of a signal that has a Feather and where would such a signal be placed.

The 'feather' is a Position Light Junction Indicator. It is to tell the driver that the route is set for the diverging route at a set of facing points. The feather will actually illuminate just before the aspect changes because if it fails and the signal clears the driver would assume that the straight route is set. If the difference in permitted speed between the straight route and turnout is more than 10mph then the clearing of the signal for the diverging route would be delayed until the train is close up to it.  

The signal with the feather would be positioned between about 20 feet from the points up to about half a mile, but the optimum distance if no other factors such as station platforms are involved would be 200 yards.

[71000]

Thanks for all the replies folks. Spotting how the signals are arranged is difficult on my local station, its on a curve, in the dark even with my face against the glass I cant see them only at red.

I think reading your replies I may as well signal the layout thus. 4 aspect on the mains, 3 aspect on the slows.

No ones going to see it may not be prototypical but then again it is my layout. Auto changing signals will just add that bit of fun.

 

Now I have another question. What is the purpose of a signal that has a Feather and where would such a signal be placed.

 

N

[TheSignalEngineer]

Regarding your last comment on the diagram, if a line is a goods running line it will have a main aspect with route indication. The comment about a shunt aspect is not correct as a shunt signal associated with a main running signal will be mounted on the same post and will not have a red aspect. For routes leading to a siding the signal the main signal will show a red aspect with two white lights displayed by the subsidiary aspect. If the subsidiary aspect applies to more than one siding route it may have a stencil or other equivalent miniature alpha-numeric route indicator added. 

The subsidiary aspect may also be used for a calling-on signal into an occupied line e.g.a station platform, or fo a shunt move to attach/detach. In these cases there is a whole raft of rules as to what route indications should be shown for each move. 

Regarding 'feathers', although there are six available positions and there is a good example of multiple indications here http://www.roscalen.com/signals/WestMids/7309/0156.jpg, nowadays there are restrictions on what positions can be used at any one signal due to the risk of misreading, 

 

More reading on the subject is availabe on the RSSB website. The current requirements are covered by this document http://www.rssb.co.uk/rgs/standards/GKGN0658%20Iss%201.pdf

[The Stationmaster]

Regarding your last comment on the diagram, if a line is a goods running line it will have a main aspect with route indication. The comment about a shunt aspect is not correct as a shunt signal associated with a main running signal will be mounted on the same post and will not have a red aspect. For routes leading to a siding the signal the main signal will show a red aspect with two white lights displayed by the subsidiary aspect. If the subsidiary aspect applies to more than one siding route it may have a stencil or other equivalent miniature alpha-numeric route indicator added. 

The subsidiary aspect may also be used for a calling-on signal into an occupied line e.g.a station platform, or fo a shunt move to attach/detach. In these cases there is a whole raft of rules as to what route indications should be shown for each move. 

Regarding 'feathers', although there are six available positions and there is a good example of multiple indications here http://www.roscalen.com/signals/WestMids/7309/0156.jpg, nowadays there are restrictions on what positions can be used at any one signal due to the risk of misreading, 

 

More reading on the subject is availabe on the RSSB website. The current requirements are covered by this document http://www.rssb.co.uk/rgs/standards/GKGN0658%20Iss%201.pdf

 

And there are of course slight variations by region/standards of the time at which the signal was installed.  Thus at Scours Lane at Reading the indication on R143 reading from the Up Relief/ R43 reading from the Up  Main to the Up Goods Line (where the next signal was a GPL) was a sub with a Position 1 Junction Indicator.

 

It was one reason why, in the 1990s, I specified fixed reds (unless there was a multi aspect signal) instead of STOP boards or GPLs at the advance end of the Goods Line/siding status loops at Southall in order to ensure that trains could enter a clear loop on a main aspect with a JI approach released instead of having to come to a stand and wait for the sub to clear.  It was actually the only way we could get trains off or across the Main Lines fast enough with the HEX service being added plus other expected increases in number of trains.  So all the fixed reds at Southall are down to me.

[71000]

Regarding your last comment on the diagram, if a line is a goods running line it will have a main aspect with route indication. The comment about a shunt aspect is not correct as a shunt signal associated with a main running signal will be mounted on the same post and will not have a red aspect. For routes leading to a siding the signal the main signal will show a red aspect with two white lights displayed by the subsidiary aspect. If the subsidiary aspect applies to more than one siding route it may have a stencil or other equivalent miniature alpha-numeric route indicator added. 

The subsidiary aspect may also be used for a calling-on signal into an occupied line e.g.a station platform, or fo a shunt move to attach/detach. In these cases there is a whole raft of rules as to what route indications should be shown for each move. 

Regarding 'feathers', although there are six available positions and there is a good example of multiple indications here http://www.roscalen.com/signals/WestMids/7309/0156.jpg, nowadays there are restrictions on what positions can be used at any one signal due to the risk of misreading, 

 

More reading on the subject is availabe on the RSSB website. The current requirements are covered by this document http://www.rssb.co.uk/rgs/standards/GKGN0658%20Iss%201.pdf

E

[shibushe]

The 'feather' is a Position Light Junction Indicator. It is to tell the driver that the route is set for the diverging route at a set of facing points. The feather will actually illuminate just before the aspect changes because if it fails and the signal clears the driver would assume that the straight route is set. If the difference in permitted speed between the straight route and turnout is more than 10mph then the clearing of the signal for the diverging route would be delayed until the train is close up to it.  

The signal with the feather would be positioned between about 20 feet from the points up to about half a mile, but the optimum distance if no other factors such as station platforms are involved would be 200 yards.

Thanks for that. Very clear explanation. 

[shibushe]

Seeing your dilema I have done you a couple of quick sketches to help you get the hang of colour light signals. I was a BR train driver, and what is shown is for colour light signalling up until privatisation. One or two detail changes have occured since BR in particular the colours displayed on shunting signals.

Note that with the 2 aspect type signal, you can only have ONE train between each of the Red/Green signals. In other words the Yellow/green type are effectively like an old fashioned distant signal, trains don't stop at them, they just give you information abouth the line ahead. On a model railway you therefore would need more space than if you used 3 or 4 aspect types. Note the advantage of the 4 aspect type gives the driver two advance warning of a red, so the braking distance is potentially extended. However braking distance on a model railway like most things on the model can be effectively shrunk. It is however normally the case that colour light signals are positioned at roughly equal distances apart, and are not usually less than the length on one train, unless the line speed is reduced to around 30mph or less (such as London Bridge-Waterloo East). When trying to cram more signals on my layout I usually take my longest train and add a couple more carriages and then use that as my measuring stick for signal spacing.

 

71000 The Duke     

Thanks for taking the trouble to give me all this info. Its now becoming clearer, I take your comment on spacing with a model railway it would be to easy to go mad. Starting now to draw up a plan of action, It wont be long before Er Indoors gives the Green light for me to disappear into the Railway Room. Best wishes.

[The Pilotman]

The WR engineer stated that if a 220yd overlap was unavailable, the train should be stopped at the previous signal until the level crossing gates had been lowered. The train should then be allowed into the station, with the starter at red, and the barriers could be opened until such time as the train was ready to leave. The Sr engineer replied that this was exactly why overlaps had been abolished in such circumstances as Londons railways & roads would be gridlocked !

 

That's very interesting; I was always under the impression that a crossing that was open to road traffic did not count as an obstruction in an overlap. I'm not sure what the set up is now but in the Reading Panel era when Colthrop crossing box was in operation (maybe it still is?) it was possible to allow a stopping train into Thatcham station in the down direction with the crossing beyond open to road traffic even though the protecting signal at the end of the platform was a matter of yards from the very busy road beyond. I know it was possible because I've done it myself.

[St. Simon]

That's very interesting; I was always under the impression that a crossing that was open to road traffic did not count as an obstruction in an overlap. I'm not sure what the set up is now but in the Reading Panel era when Colthrop crossing was in operation (maybe it still is?) it was possible to allow a stopping train into Thatcham station in the down direction with the crossing beyond open to road traffic even though the protecting signal at the end of the platform was a matter of yards from the very busy road beyond. I know it was possible because I've done it myself.

At least nowadays we don't call or prove Level Crossings down in the Overlap.

 

Simon

[The Stationmaster]

Exactly why I stated that what I have drawn relates to the situation under BR. As the "Stationmaster" points out there were also regional differences under BR. Indeed I had a WR & an SR signalling engineers in my cab one day (Class 455 EMU), who began an argument about the dangers or otherwise of allowing a train into a station with a very busy level crossing at the far end while cars were crossing and the only protection was a red signal positioned just 50ft (less than a carriage length) from the crossing. The station being Motspur Park. This was soon after the then new Wimbledon computer signalling centre had taken control. The SR engineer stated it was impossible to have old fashioned safety rules for this situation as both the train service (very intense in the rush hour) and the road (extremely busy in SW London) would be gridlocked.

The WR engineer stated that if a 220yd overlap was unavailable, the train should be stopped at the previous signal until the level crossing gates had been lowered. The train should then be allowed into the station, with the starter at red, and the barriers could be opened until such time as the train was ready to leave. The Sr engineer replied that this was exactly why overlaps had been abolished in such circumstances as Londons railways & roads would be gridlocked !

What neither signal engineer had considered was the notorious "3 step brake" fitted in class 455 and similar multiple units at that time. The 3 step brake with its anti-skid system taken from the motor industries car ABS system, simply did the opposite of what was needed. If this system actuated due to wheel slip, it could extend a trains braking distance from 90mph and around 1 mile to stop to as much as 3 miles (The Andover incident with a class 159 DMU). On suburban units travelling at probably no more than 50mph between suburban stations, the evil 455 could still skid an extra 800-1200yds. Which in Motspur Parks case would have resulted in probably wiping out at least a couple of cars on the crossing.....       

 

Sounds like somebody had got their 'old fashioned' an confused.  Under Absolute Block Signalling a train can be accepted under full Line Clear up to a Home Signal (the outermost Home Signal in order to remove doubt) which might only be a matter of feet from a level crossing which it protects and on which the gates are open to road traffic.  (In other words the rough equivalent of having a level crossing in an overlap with the signal in rear of the protecting signal able to clear to a proceed aspect)

[The Stationmaster]

At least nowadays we don't call or prove Level Crossings down in the Overlap.

 

Simon

Was it ever done Simon?  (Possibly in E10,000 circuits but not otherwise I suspect although no doubt Signal Engineer will be along to help us out - 

 

That's very interesting; I was always under the impression that a crossing that was open to road traffic did not count as an obstruction in an overlap. I'm not sure what the set up is now but in the Reading Panel era when Colthrop crossing was in operation (maybe it still is?) it was possible to allow a stopping train into Thatcham station in the down direction with the crossing beyond open to road traffic even though the protecting signal at the end of the platform was a matter of yards from the very busy road beyond. I know it was possible because I've done it myself.

Can you remember what it was like at Causeway and Appleford as they were much older design circuitry than the B&H crossings?  (Although I'm fairly sure scratching back a long way in memory that the same applied at Worle and the crossing wasn't an obstruction in the overlap - i.e. effectively roughly the same as an Absolute Block Clearing Point).

please)

[uax6]

Of course you also have those locations where you have a mix of 2 and 3 aspect heads (and I suppose 4 aspect too). I'm sat in a box where although we work track circuit block, our coloured lights are closer to absolute block. in the down we have 2 aspect distant, three aspect 'home' and two aspect 'starter'. In the up we have two aspect distant, three aspect 'first home', three aspect 'second home' and two aspect 'starter'.

 

Andy G