When a signal has these two arms on the same post, obviously the home signal relates to that point on the track but the distant gives information about the next home signal down the track. This much I know. I am interested in the sequence of the signal indications:
I think the sequence is (but please correct me if I am wrong):
First , both signals at danger.
Next, distant remains at danger home at clear.
Next, both signals at clear.
Train passes.
But what happens now? Obviously they both need to return to danger. Which is normally returned to danger first?
I should be very grateful for any information on this. My books on signalling do not mention this issue and my trainspotting days were 60+ years ago and I can't remember. I am hoping to construct a correctly operating signal. Thanks
Signalling, home and distant on same post
Re: Signalling, home and distant on same post
The distant in semaphore signalling areas can only be cleared to Off if all the section signals ahead are also clear. That is all signals ahead belonging to that block section are set to Off (proceed), if any is On then the distant can not be cleared. A distant arm that is in the On position can be passed at caution, but the driver of the train should reduce the trains speed so as to be able to stop at the next signal. I have tried to cover this here if it helps? https://www.brian-lambert.co.uk/Hints_& ... #Bookmark9
<< Click the Icon to go to my websiteRe: Signalling, home and distant on same post
Thanks for this, Brian.
So the home signal will always return to danger as soon as the train has passed. The signalman will do this immediately. If the distant signal had been cleared to proceed before the train passed then the road would presumably still be clear but semaphore signals were usually returned to danger after use. Would this be simultaneous with the home signal being returned to danger or slightly afterwards? I guess the latter.
Thanks also for the link to your website which is helpful.
So the home signal will always return to danger as soon as the train has passed. The signalman will do this immediately. If the distant signal had been cleared to proceed before the train passed then the road would presumably still be clear but semaphore signals were usually returned to danger after use. Would this be simultaneous with the home signal being returned to danger or slightly afterwards? I guess the latter.
Thanks also for the link to your website which is helpful.
Re: Signalling, home and distant on same post
Yes the signaller for that section will restore the signal to danger once the train has passed. Returning both main and distant arms if both were Off. He doesn't want another train coming up behind the first and getting any proceed aspects while the section is occupied, as the result would likely to be catastrophic! 
<< Click the Icon to go to my website
Re: Signalling, home and distant on same post
Here at Whittington the Starter is 'off' But Barrow Hill South's distant is' 'on'. Not only that but because Barrow Hill Station is only a short way away from Barrow Hill South is only a short way from Barrow Hill Station both these signalmen have 'slots' on the distant at Whittington at least so far as the main line is concerned. To clear the distant at Whittington, Barrow Hill South, and Barrow Hill Station all have to have all their signals cleared.
If the signals are cleared for the slow line instead of the main line the signals on the left would be cleared instead,
Because both Barrow Hill South and Barrow Hill Station are so close they also have distant signals under their stop signals.
Whittington
Barrow Hill South signals
If the signals are cleared for the slow line instead of the main line the signals on the left would be cleared instead,
Because both Barrow Hill South and Barrow Hill Station are so close they also have distant signals under their stop signals.
Whittington
Barrow Hill South signals
LC&DR says South for Sunshine
Re: Signalling, home and distant on same post
If we're talking about 'real life' UK railway practice here, there are various different scenarios in which a semaphore distant arm may be on the same post as a stop signal arm (the term home signal is historically used to mean the first stop signal a train encounters on approaching a signalbox, and it represents the end of the block section between two boxes - however these days all signals capable of displaying a 'stop' aspect are called 'stop' signals, and those whose most restrictive possible aspect is yellow are called 'distant' signals. The historical terms, however, are still commonly used).
One once common scenario, in Absolute Block areas (where trains are controlled on the principle of only one train occupying the section of line between two signal boxes at any one time), the distant signal is positioned a braking distance away from the first stop signal, and if cleared, indicates to a driver that all stop signals controlled by that box are also clear. Usually the distant will be on its own post, however if a block section is particularly short, the distant signal for one box may be on the same post as the outermost stop signal of the box in rear. In this case, the stop signal arm is controlled by one box (say, Box A), but the distant arm is controlled by another (Box B). However, where this occurs, an interlocking mechanism on the post itself means the distant arm can only clear if the stop arm is also clear. So signalman B may have all his signals 'off' and thus can pull the distant lever in his box, but if his colleague signalman A still has his last stop signal 'on' then the distant arm will remain horizontal, in order to avoid confusion for drivers. So to answer the question asked, in this case, the stop arm can be cleared with the distant at caution, but the distant arm cannot be cleared when the stop signal is at danger. If both are cleared, then the distant arm may be replaced to caution with the stop arm still clear, however signalling regulations are such that this should never be done in sight of an approaching train - ie. a driver should never see a signal ahead of him become more restrictive as he approaches it. If the home arm is replaced to danger (in emergency, or following the passage of a train) then the distant arm, if still off, will revert to caution simultaneously with the stop arm.
Another possible scenario is in locations where there is a transition from Absolute Block with semaphores, to Track Circuit Block with colour lights. At the point of transition, the last semaphore signal may also have a distant arm, configured such that the distant arm is a 'repeater' for the next signal (a colour light). In this case, the distant arm would show caution if the next signal is at danger (red), or clear if the next signal is showing a proceed aspect (yellow or green). However, as above, the distant arm is ALWAYS interlocked such that it can NEVER be clear unless the stop arm is also clear. A driver would interpret such a signal as 'red/danger' (both arms on), 'yellow/caution' (stop arm off, distant arm on), or 'green/clear' (both arms off).
Hope that answers the question!
One once common scenario, in Absolute Block areas (where trains are controlled on the principle of only one train occupying the section of line between two signal boxes at any one time), the distant signal is positioned a braking distance away from the first stop signal, and if cleared, indicates to a driver that all stop signals controlled by that box are also clear. Usually the distant will be on its own post, however if a block section is particularly short, the distant signal for one box may be on the same post as the outermost stop signal of the box in rear. In this case, the stop signal arm is controlled by one box (say, Box A), but the distant arm is controlled by another (Box B). However, where this occurs, an interlocking mechanism on the post itself means the distant arm can only clear if the stop arm is also clear. So signalman B may have all his signals 'off' and thus can pull the distant lever in his box, but if his colleague signalman A still has his last stop signal 'on' then the distant arm will remain horizontal, in order to avoid confusion for drivers. So to answer the question asked, in this case, the stop arm can be cleared with the distant at caution, but the distant arm cannot be cleared when the stop signal is at danger. If both are cleared, then the distant arm may be replaced to caution with the stop arm still clear, however signalling regulations are such that this should never be done in sight of an approaching train - ie. a driver should never see a signal ahead of him become more restrictive as he approaches it. If the home arm is replaced to danger (in emergency, or following the passage of a train) then the distant arm, if still off, will revert to caution simultaneously with the stop arm.
Another possible scenario is in locations where there is a transition from Absolute Block with semaphores, to Track Circuit Block with colour lights. At the point of transition, the last semaphore signal may also have a distant arm, configured such that the distant arm is a 'repeater' for the next signal (a colour light). In this case, the distant arm would show caution if the next signal is at danger (red), or clear if the next signal is showing a proceed aspect (yellow or green). However, as above, the distant arm is ALWAYS interlocked such that it can NEVER be clear unless the stop arm is also clear. A driver would interpret such a signal as 'red/danger' (both arms on), 'yellow/caution' (stop arm off, distant arm on), or 'green/clear' (both arms off).
Hope that answers the question!
Re: Signalling, home and distant on same post
As well as having a 'distant' signal under a stop signal as a precursor to entering a colour light (TCB) area, acting as the first 'yellow' aspect and repeating a red at the first colour light, another way of doing this was to fit a two or three aspect colour light head beneath the most advanced stop signal at the final signalbox before the TCB area. When the stop signal is at danger the colour light aspects are extinguished. The normal red spectacle of the semaphore giving the night time danger indication. However when the stop signal is cleared the colour light head is illuminated and a single yellow, double yellow or green aspect is displayed, as appropriate.
The application of this I was most familiar was Blackheath 'B' up starter, leading into the St. Johns TCB area, in South East London.
The application of this I was most familiar was Blackheath 'B' up starter, leading into the St. Johns TCB area, in South East London.
LC&DR says South for Sunshine
Re: Signalling, home and distant on same post
Thanks to Brian, LC & DR and Biskit, who in combination have answered my question.
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Re: Signalling, home and distant on same post
Just to add a little detail. Absolute block lines with semaphore signals are often also track circuited and one will know this with a little white diamond sign displayed on rhe post of the semaphore signal.
Not to confuse things, all this basically is, is a simple track circuit used where the train acts as a "Switch" to close a circuit so the signal box has a reminder indication that there is a train in the section.
If trains have not been run on the line for a day or two, the first two trains to pass may not be displaying on the signal box panels so they operate as standard absolute block signal boxes until they get their displays back working. It is just until the thin rust on the track surface is cleared by the passing trains so their track circuits are working again.
Automatic and semi automatic signalling areas rely on track circuits to work to run trains. If they have not been used for a while... Well... I have seen lots of PW workers along a route all signalling trains to pass with flags, each man standing at a signal.
Safety is ALWAYS the priority.
Out if interest, some lighter weight trains like some sprinters, pacers etc. may be too light to operate all the track circuits. They had to have a high frequency electronic device fitted which is basically the same as an electronic track cleaner used for model railways like Relco, but this is mounted onto the train rather then the track. The idea is that the electronic high frequency device will shift just enough grime or dirt so its wheels can operate the track circuits. The heavier trains will not habe a problem as they are heavy enough to operate the track circuits without any problems.
Also seen on the track are little treddles to operate crossings along with the AWS and TPWS devices.
Another interesting trackside aperatus is used where sharp curves are in the area along with check rails which are greasers, which every time a train passes, it applies grease to the track to reduce wheel wear and rail wear, and help trains round rhe corners. I have in the past become stuck on that curve out of Swansea on long wheelbase class 143's or 142's if the track is dry in the summer! Ice can also cause issues. I remember on more then one occasion needing to jump up and down over the power bogies of a 158 to get up the hill leaving Tenby with icy rails. The problem with those 158's was that only two wheels were driven (Or was it four? I believe it was only two) and jumping up and down even though my weight was not going to do too much, was just enough to help the wheels grip. They then tried 143's with the theory being that with just 4 wheels, there was more weight on the 4 wheels but nope. They were just as bad. It was only the first service in the morning rhat had the issues. After then trying a 153 which was a little better (They were used up the Heart Of Wales line which often was iced up) but even these sometimes failed to get up the hill, they tried the 150's which were the only units which could reliably make it! So the first morning service in the winter timetable had to be a class 150 for that line.
It can be funny when things get forgotton about over time and someone in an office without experience decides to use book in a different unit where older traincrew and office staff knew it would not work... And history repeats itself!
Like the time someone decided to send me a class 158 to work up the Heart of Wales railway and I had to refuse to take it up and control asked me why, and I had to tell them why there was a rule they should not be worked up there. It was because of the angles of a certain platform with the height of the platform meant that the doors could not be opened as the doors opened outwards and would hit the platform. I think it was at Llandybie or Llangadog stations? One of those. I was lucky to leave when I heard they wanted to take the 175's up there. Trying to work that line was often an energetic experience for a guard and the 175's which at the time could only be keyed in from the back cab to release the doors (Apart from a single door half way down the train for a short platform)... The thought of trying to work a 175 up there was "NOOOO!"
They were hard enough to work on the main line with fewer stops, and the aching back through working the 175's! (Conductors who have worked them will know what I mean!
"Time to leave!" Actually, if it wasn't for the sharp curves at the Shrewsbury end of the line, class 143's were the easiest trains to work up there, but if we took one up we had to get the passengers to swap trains to go further then Llanwrtyd or Llandridod, and we had to take the 143 back down. The passengers loved them because they had lower windows, so they could see better views, as rhe 150's and 153's they tended to work had higher windows, and many passengers were not quite tall enough to look out to see the views.
Not to confuse things, all this basically is, is a simple track circuit used where the train acts as a "Switch" to close a circuit so the signal box has a reminder indication that there is a train in the section.
If trains have not been run on the line for a day or two, the first two trains to pass may not be displaying on the signal box panels so they operate as standard absolute block signal boxes until they get their displays back working. It is just until the thin rust on the track surface is cleared by the passing trains so their track circuits are working again.
Automatic and semi automatic signalling areas rely on track circuits to work to run trains. If they have not been used for a while... Well... I have seen lots of PW workers along a route all signalling trains to pass with flags, each man standing at a signal.
Safety is ALWAYS the priority.
Out if interest, some lighter weight trains like some sprinters, pacers etc. may be too light to operate all the track circuits. They had to have a high frequency electronic device fitted which is basically the same as an electronic track cleaner used for model railways like Relco, but this is mounted onto the train rather then the track. The idea is that the electronic high frequency device will shift just enough grime or dirt so its wheels can operate the track circuits. The heavier trains will not habe a problem as they are heavy enough to operate the track circuits without any problems.
Also seen on the track are little treddles to operate crossings along with the AWS and TPWS devices.
Another interesting trackside aperatus is used where sharp curves are in the area along with check rails which are greasers, which every time a train passes, it applies grease to the track to reduce wheel wear and rail wear, and help trains round rhe corners. I have in the past become stuck on that curve out of Swansea on long wheelbase class 143's or 142's if the track is dry in the summer! Ice can also cause issues. I remember on more then one occasion needing to jump up and down over the power bogies of a 158 to get up the hill leaving Tenby with icy rails. The problem with those 158's was that only two wheels were driven (Or was it four? I believe it was only two) and jumping up and down even though my weight was not going to do too much, was just enough to help the wheels grip. They then tried 143's with the theory being that with just 4 wheels, there was more weight on the 4 wheels but nope. They were just as bad. It was only the first service in the morning rhat had the issues. After then trying a 153 which was a little better (They were used up the Heart Of Wales line which often was iced up) but even these sometimes failed to get up the hill, they tried the 150's which were the only units which could reliably make it! So the first morning service in the winter timetable had to be a class 150 for that line.
It can be funny when things get forgotton about over time and someone in an office without experience decides to use book in a different unit where older traincrew and office staff knew it would not work... And history repeats itself!
Like the time someone decided to send me a class 158 to work up the Heart of Wales railway and I had to refuse to take it up and control asked me why, and I had to tell them why there was a rule they should not be worked up there. It was because of the angles of a certain platform with the height of the platform meant that the doors could not be opened as the doors opened outwards and would hit the platform. I think it was at Llandybie or Llangadog stations? One of those. I was lucky to leave when I heard they wanted to take the 175's up there. Trying to work that line was often an energetic experience for a guard and the 175's which at the time could only be keyed in from the back cab to release the doors (Apart from a single door half way down the train for a short platform)... The thought of trying to work a 175 up there was "NOOOO!"
They were hard enough to work on the main line with fewer stops, and the aching back through working the 175's! (Conductors who have worked them will know what I mean!"Time to leave!"
Actually, if it wasn't for the sharp curves at the Shrewsbury end of the line, class 143's were the easiest trains to work up there, but if we took one up we had to get the passengers to swap trains to go further then Llanwrtyd or Llandridod, and we had to take the 143 back down. The passengers loved them because they had lower windows, so they could see better views, as rhe 150's and 153's they tended to work had higher windows, and many passengers were not quite tall enough to look out to see the views.Budget modelling in 0-16.5...
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