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Distant at caution 26/05/2018 at 00:07 #108227 | |
TUT
514 posts |
Something that's always had me confused when it comes to absolute block is what happens after a train passes a distant at caution. I'm sure I've read at various times and in various places that if all the stop signals are not able to be cleared then the train should be brought almost to a stand at the home signal, which should then be cleared. The train must then be brought almost to a stand at the next signal and so on up to the section signal. Until, that is, all of the signals that a train has yet to pass can be cleared, at which point they should all be cleared. Thus, if a train passes a distant at caution the driver should expect to stop at the home signal. Finding the home signal on he should then brake and, if the home signal can be cleared, it will then clear as the train brakes. The driver must then expect to stop at the next signal and the process will repeat. However, if, after passing the distant at caution, or after passing one/some of the stop signals, the (rest of) the stop signals can all be cleared, they will be cleared. Thus, if, after passing the distant at caution, the driver finds the home off (or the next stop signal off) and he is not brought almost to a stand at it, he can happily assume that all further signals will be off and accelerate up to full line speed. But. This doesn't really appear to be how things work in SimSig, where we can happily clear some stop signals, but not all, for a train, with no messing about with bringing trains almost to a stand. The manual for a couple of Scottish sims describes an off stop signal encountered after passing a distant at caution as behaving like a caution signal, with trains limited to 40 mph. Perhaps this is just a limitation of SimSig, a best approximation. But it would make sense if things worked this way too and I've never been able to observe the sequence of events I described in any cab ride videos or anything, and I'm really wondering, what with 3-aspect homes and everything, whether there hasn't been a change to the rules. But I can't find anything for certain. So. How does it work. In real life, if you're a signalman and you can clear some of your stop signals, but not all, can you? Or do you have to go through the whole bring the train almost to a stand at each stop signal palaver? If you're a driver and you pass a distant at caution but see the home signal off, do you have to remember your distant, hold back, not assume that all signals are off and instead proceed at caution (surely not 40 mph if you're driving a freight train as some stop signals are very close together?) Or can you open up and accelerate to full line speed, safe in the knowledge that if one's off, they must all be? Last edited: 26/05/2018 at 00:09 by TUT Reason: None given Log in to reply |
Distant at caution 26/05/2018 at 00:17 #108228 | |
Steamer
3958 posts |
TUT in post 108227 said:How does it work. In real life, if you're a signalman and you can clear some of your stop signals, but not all, can you? Or do you have to go through the whole bring the train almost to a stand at each stop signal palaver?This definitely still happens- I was at Gilberdyke last year, and saw it happen with to a freight train from Selby that was approaching just after a stopping service left. I don't think the freight was brought to a stand at any point (or it may have been stopped at the outer home as the stopper came off the branch). Quote: If you're a driver and you pass a distant at caution but see the home signal off, do you have to remember your distant, hold back, not assume that all signals are off and instead proceed at caution (surely not 40 mph if you're driving a freight train as some stop signals are very close together?) Or can you open up and accelerate to full line speed, safe in the knowledge that if one's off, they must all be?I think it's a safe bet that defensive driving policies these days would require a driver to observe the last signal as clear before accelerating away. I'm sure Mr. Barber will be along in due course to tell us how it used to be done! Most simulations don't enforce the 'bring almost to a stand rule', but a couple do- Saltley implements it automatically (so you can set the route but the signals won't clear until the appropriate conditions are met). "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Last edited: 26/05/2018 at 00:20 by Steamer Reason: None given Log in to reply The following user said thank you: TUT |
Distant at caution 26/05/2018 at 00:24 #108229 | |
TUT
514 posts |
Steamer in post 108228 said:TUT in post 108227 said:That's really interesting You know I was really quite convinced this information was out of date and things must just have changed.How does it work. In real life, if you're a signalman and you can clear some of your stop signals, but not all, can you? Or do you have to go through the whole bring the train almost to a stand at each stop signal palaver?This definitely still happens- I was at Gilberdyke last year, and saw it happen with to a freight train from Selby that was approaching just after a stopping service left. I don't think the freight was brought to a stand at any point (or it may have been stopped at the outer home as the stopper came off the branch). So, on the subject of freight trains, if you've got a heavy freight train going into a loop, and the line is all clear into the loop and the points are all set for it and everything, you still have to bring the train almost to a stand at each signal until it finally berths in the loop? Even if there are three our four signals? If so, have there ever been any local arrangements, or unique signals to speed this whole process up? Just for my own personal interest Log in to reply |
Distant at caution 26/05/2018 at 00:25 #108230 | |
MarkC
1099 posts |
In the case of semaphore signals the distant signal will normally only clear if all the stop signals under the control of the signalbox show clear.
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Distant at caution 26/05/2018 at 00:47 #108232 | |
TUT
514 posts |
MarkC in post 108230 said:In the case of semaphore signals the distant signal will normally only clear if all the stop signals under the control of the signalbox show clear.Quite correct! :) The question is, what if some of the stop signals can be cleared, but not all? Say the block section ahead is occupied and so the section signal can't be pulled off. Or perhaps the train is due to be shunted into a siding or put into a loop. Or, from another point of view, imagine you're a train driver and you pass a distant at caution. Now you sight the home signal and it's off. What does it mean? Does it mean that all the signals are off, having been cleaned after you passed the distant? Or does it mean nothing more or less than that the home signal is off and do you still have to proceed at caution, expecting to find the next signal on? Log in to reply |
Distant at caution 26/05/2018 at 01:03 #108233 | |
MarkC
1099 posts |
If the distant is at caution in most cases all but the starting signal can be cleared, (local instuction may differ) In the part you asked about having passed the distance at caution but then sight the home at clear it does not mean that you have a clear run though the section you would in essence still slow down as at the time of approching the home the section ahead is still blocked, the only time a driver can assume a clear run though is only if the distance signal shows a clear. Log in to reply |
Distant at caution 26/05/2018 at 01:22 #108234 | |
TUT
514 posts |
MarkC in post 108233 said:If the distant is at caution in most cases all but the starting signal can be cleared, (local instuction may differ)That's what I thought! Or at least, that's what I thought the new rules must be. I have now done a bit more digging and found the old rule 39 from BR days: Quote: When a stop signal is at Danger the stop signal next in rear of it and worked from the same signal box must not be lowered for an approaching train until the train is close to such signal and has been brought quite or nearly to a stand. (more)To quote this page: Quote: Taking account of the description of Rule 39 above, it can be seen that if a driver passes a distant signal at on, he will be prepared to find the stop signal ahead on, but if that signal is off (without his brought nearly to a stand) he can expect all stop signals ahead (worked by that box) to be off. Log in to reply |
Distant at caution 26/05/2018 at 03:02 #108235 | |
Stephen Fulcher
2055 posts |
In reality it's normally down to the Signalman to use his own discipline to bring a train nearly to a stand at each signal - it's rare for Interlocking to enforce it. The Leamington sim replicates a partial example of this in the 2003 era whereby FC46 is restricted by a train between it and FC103, you cannot clear it unless its berth track is occupied or be previous train has cleared FC103, but the other stop signals in the area rely on the Signalman to obey the rules. Log in to reply |
Distant at caution 26/05/2018 at 06:05 #108237 | |
DriverCurran
685 posts |
MarkC in post 108230 said:In the case of semaphore signals the distant signal will normally only clear if all the stop signals under the control of the signalbox show clear.And if there is a splitting junction and no splitting distant then you can only clear the distant if all the stop signals for the fastest route are clear Paul You have to get a red before you can get any other colour Log in to reply |
Distant at caution 26/05/2018 at 10:28 #108243 | |
kbarber
1723 posts |
As always with old fashioned signalling, there's lots of complications. But essentially, you do have to bring the train almost to a stand at each signal in turn and it is all down to the signalman to do the job right. A driver having had a distant at caution should never assume anything, even if the home is clear as he approaches; the signalman may have pulled off early (we did sometimes need to visit the 'East Wing', sometimes hurriedly - there's a limit to how long the human body can hold on, especially with the amount of tea drunk in a signalbox). Of course, if the starter's visible on approaching the home, the driver can see what's going on and can drive accordingly. There were locations where an exception to the rule was specifically authorised. In that case there would be an entry in the Sectional Appendix. Several stations on the Ely - Norwich route used to have such exemptions - the Appendix specified that the rule (in Section C in my day IIRC) would not apply to trains booked to call at those stations and that the driver could expect the home to be cleared with the starter at danger. In each case there was a level crossing on the approach side of the station, so this both gave the passengers a smoother ride and cleared the crossing more quickly. The Rule Book specified an exception to the rule where the home (and others) was a colour light signal with full braking distance to the following stop signal; in that case, you just pulled off. Where there wasn't braking distance, you had to apply the rule, even though you had a 3-aspect colour light home; in some cases (but by no means all) you could reverse the lever and, if the signal ahead was at danger, the signal would remain red until the berth track was occupied (with or without a timer to enforce a further delay). Unless there is an exemption (either in the Sectional Appendix or the SBSIs), I don't believe there is any authority to clear the home early for a train being looped. For any junction, unless there is a splitting distant the requirement for a train on the diverging route is to keep the home at danger until the train approaches it unless it is booked to take the diverging route. (That would particularly apply on a 4-track railway, of course). If the signal is an approach-released colour light the lever can be reversed at any time, and of course that means all trains for the diverging route would be checked. There was also an exemption for densely trafficked suburban areas, where the signal for the diverging route could be cleared as soon as possible. Log in to reply The following user said thank you: TUT |
Distant at caution 26/05/2018 at 17:52 #108263 | |
TUT
514 posts |
kbarber in post 108243 said:As always with old fashioned signalling, there's lots of complications. But essentially, you do have to bring the train almost to a stand at each signal in turn and it is all down to the signalman to do the job right.Thank you very much for this! It's just the kind of thing I was hoping for Log in to reply |
Distant at caution 26/05/2018 at 20:29 #108268 | |
TUT
514 posts |
Just found this in the general signalling regulations: Quote: 4.5 Clearing a stop signal when the next signal is at danger Log in to reply |
Distant at caution 26/05/2018 at 21:54 #108274 | |
clive
2766 posts |
Current rule book GERT8000-S7 Iss 3, applying to drivers: Quote: This suggests that, for those types of signals, if it's already clear then you don't need to worry about the rest of the signals controlled by that box. Log in to reply The following user said thank you: TUT |
Distant at caution 27/05/2018 at 10:58 #108287 | |
Late Turn
697 posts |
clive in post 108274 said:Current rule book GERT8000-S7 Iss 3, applying to drivers: The 'signals (etc.) handbook', RS521, also only makes reference to being "prepared to stop at the next stop signal" when giving the meaning of a distant signal at caution, which supports that. If you've encountered the distant signal at caution, I can't see anything in the Rule Book relating to stop signals in advance of the (outermost) home signal if the above clause isn't applied. I can't remember the typical wording of the exemptions from that clause (in the Sectional Appendix?), but presumably they fill that gap for those specific locations. However, I'm sure that most TOCs teach drivers to expect to find any of the associated stop signals at danger if the distant has been passed at caution, irrespective of the way that those stop signals are worked. My TOC certainly does, and it's detailed in the train driving policy too. That said, before I left for the dark side, I certainly observed some drivers (primarily freight!) who put a lot of trust in my correct working of signals. One in particular stands out, who'd passed the distant at caution only a few seconds before I was able to clear the home and the starter - at that time, both signals would've been out of sight to the driver. Obviously he'd had the brake in straight away, but took power as soon as he saw the home signal cleared (it would've come into view about halfway from the distant, so quite a way away). The section signal was tucked away out of sight around a curve, relatively poorly sighted with a bridge intervening too, and he'd have had no chance of stopping if I had kept it at danger (in which case, of course, I'd have made sure that the train was nearly stopped at the home signal before clearing it*). I recall a SPAD in similar circumstances, at a different location - the home signal had been cleared far too soon, meaning that the driver was misled into thinking that the section signal was cleared when it had been held at danger. I'm pretty sure that the driver was exonerated, at least as far as Network Rail were concerned, again supporting the view that they consider it reasonable for drivers to be led to believe that the first one off (without being checked down) means that they're all off, even if the TOCs disagree! Regarding trains signalled into loops - at Melton, the signal controlling entry to the Up Loop was a colour-light signal with an approach-controlled subsidiary indication reading into the loop. There were two semaphore stop signals in rear of this, and we did indeed have to check trains down at each of these in turn - "nearly at a stand" is obviously open to interpretation, but in practice they'd just trundle along steadily once the (first) home signal was cleared, and I'd clear the second one once it was clearly visible to them. * - easier said than done at that location, as the home signal was barely visible from the box and a train stopped at it even less visible, and the track circuit in rear was the best part of a mile long, so you never really knew exactly where the train was. Read the RAIB report into the bad SPAD at Greenford to see their take on a similar setup! Log in to reply The following user said thank you: TUT |
Distant at caution 27/05/2018 at 17:17 #108294 | |
jc92
3649 posts |
Barnham junction was able to clear it's home into the platform loop for a train off the Bognor branch IF the train was booked to Terminate. As an interesting opposite trains which are being rerouted from one Line to another (eg fast to slow) also have to be brought to a stand even I the full route is clear if they aren't booked to change lines and the crossover speed is sufficiently low. The last place I'm aware of this applying is barnetby east. "We don't stop camborne wednesdays" Log in to reply The following user said thank you: TUT |
Distant at caution 28/05/2018 at 14:27 #108310 | |
Danny252
1461 posts |
An "interesting" side effect of checking down trains at semaphores (or with colour lights released from red) is that drivers can get into the habit of assuming the signal will clear as they approach it - situations like coming into a loop or a bay platform mentioned already. There's certainly a good number of anecdotes (and probably accidents) related to drivers passing, or nearly passing, a semaphore they expected to clear before they reached it. I've certainly checked a few trains quite harshly when the driver seemed a bit too complacent in the belief that I'd clear it for him! Log in to reply The following user said thank you: TUT |
Distant at caution 29/05/2018 at 22:04 #108336 | |
Forest Pines
525 posts |
Late Turn in post 108287 said:Would this be the incident at Greenford in 2014? The report makes interesting reading. https://www.gov.uk/raib-reports/unauthorised-entry-of-a-train-onto-a-single-line-at-greenford Log in to reply |
Distant at caution 29/05/2018 at 22:21 #108337 | |
Late Turn
697 posts |
Forest Pines in post 108336 said:Would this be the incident at Greenford in 2014? The report makes interesting reading. That's the one. Broadly, the first semaphore stop signal (after a colour-light signal displaying a single yellow) was cleared long before the train was "quite or nearly at a stand" at it, possibly misleading the driver into thinking that he had the road right through. The track circuit in rear of that signal was long, so there'd be no way of knowing exactly where the train was or when it was nearly at a stand. It was (and presumably still is) similar at Melton - you could see the train on the tail lamp camera as it passed the home signal, but it was a long way to the first semaphore stop signal from there so it took a bit of careful judgement (guesswork?) to make sure that you didn't pull it off too early. Log in to reply |
Distant at caution 30/05/2018 at 16:35 #108345 | |
Zoe
251 posts |
On the GWR, there were some locations where there was not sufficient braking distance between the outermost home signal of box A and the outermost home signal of box B so to avoid having to resort to regulation 4A, box B had control of A's distant. If B was unable to obtain line clear from C then A's distant would remain at caution even if A had pulled off all their signals. In some cases however I note that no distant arm was provided below A's home signal and so even though the train would have been cautioned at A they would then see a clear home signal before sighting the starting/inner home signal with a distant for A below at caution. I asked elsewhere about the risk of a train accelerating upon seeing the first home signal clear and accelerating towards box B before seeing the distant (on the same post as A's starting/inner home) at caution but was told that the driver was never to assume that the line was clear through if they had passed a distant a caution, regardless of if the outermost home had been cleared or not. I wonder in this case if the drivers would have known that the distant was controlled by both boxes. Box A Distant (Controlled by B) -------- Box A Home ---------- Box A Inner Home/Box B Distant -------- Box B Home Last edited: 30/05/2018 at 16:44 by Zoe Reason: None given Log in to reply |
Distant at caution 30/05/2018 at 17:43 #108346 | |
TUT
514 posts |
Can I just say a very big thank you to all who have contributed here :) I'm very very glad I asked now! Log in to reply |
Distant at caution 31/05/2018 at 08:56 #108352 | |
Haraubrad
103 posts |
Banbury Junction back in the semaphore days, had 6 distant signals on the down main. the distant was under Banbury Norths advanced starter, repeater under BNs starter, repeater under BNs home, repeater under Banbury Souths starter, repeater under BSs inner home, and repeater under BSs outer home. It was fascinating to watch the indicators come off one after the other. Aubrey Log in to reply |
Distant at caution 31/05/2018 at 09:06 #108353 | |
kbarber
1723 posts |
Zoe in post 108345 said:On the GWR, there were some locations where there was not sufficient braking distance between the outermost home signal of box A and the outermost home signal of box B so to avoid having to resort to regulation 4A, box B had control of A's distant. If B was unable to obtain line clear from C then A's distant would remain at caution even if A had pulled off all their signals. In some cases however I note that no distant arm was provided below A's home signal and so even though the train would have been cautioned at A they would then see a clear home signal before sighting the starting/inner home signal with a distant for A below at caution. I asked elsewhere about the risk of a train accelerating upon seeing the first home signal clear and accelerating towards box B before seeing the distant (on the same post as A's starting/inner home) at caution but was told that the driver was never to assume that the line was clear through if they had passed a distant a caution, regardless of if the outermost home had been cleared or not. I wonder in this case if the drivers would have known that the distant was controlled by both boxes.Other railways provided slots or used 'indicator working', where box B's distant lever also operated an indicator in A (often with a bolt so A couldn't clear the distant until B had done so). At Junction Road https://signalbox.org/diagrams.php?id=706 lever 28 down distant from Gospel Oak was thus provided, the indicator being an illuminated visual showing 'free' when Upper Holloway pulled off; an electric lock was provided on 28 and, interestingly, the lever had a white band (generally considered to be improper under these circumstances). 25 (down distant from, successively, Mortimer Street, Engine Shed & West Hampstead) had no such control. The difference was down to the gradients - a steep descent all the way from Gospel Oak, and a sharp little climb from nearly-level track coming from Mortimer Street. Out on the main line, by contrast, Finchley Road had slots (worked by outer distant lever 23) on West Hampstead's up fast distants (which were, in turn, under Watling Street's home and starter). Therefore a caution at Watling Street home might mean either West Hampstead home at danger, or all clear through West Hampstead and Finchley Road home at danger, a case where proper working of the home signal was pretty much indispensible. In general, of course, a driver would be expected to know the meaning and application of all signals on routes he signed for, so the situation described by Zoe should not cause too many problems. Log in to reply |