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Post by dave1 on Jul 2, 2017 8:45:24 GMT
Anyone know anything about a number that occurred in 1990 at the following places.
Loughton
Bow Road
Barons Court
White City
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Post by railtechnician on Jul 3, 2017 3:40:08 GMT
I'm afraid not, at that time I was a CET on comms installation doing Central line enabling works at Tottenham Court Road, Chancery Lane, Liverpool Street, Bank/Monument and elsewhere.
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Post by dave1 on Jul 6, 2017 11:36:26 GMT
I think over the years there must have been many wrong side failures well reported as such but later found to be for a different reason. I bet that they don't really say exactly why though.
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Post by railtechnician on Jul 6, 2017 14:44:49 GMT
I think over the years there must have been many wrong side failures well reported as such but later found to be for a different reason. I bet that they don't really say exactly why though. I'm not sure what you are getting at here. All failures were/are thoroughly investigated to determine the exact cause and then take appropriate action. It is a fact that potential wrong side failures exist within signalling systems but they often go unnoticed until a particular set of circumstances highlights one. One such example was the failure of a track relay remaining mechanically stuck up as a result of the bearing material having been changed. It could have been disastrous as the relay had probably been stuck up more than once before it was discovered, in fact it might have been stuck up for weeks, the signal selection was such that the one relay stuck up could not on its own have caused a signalling failure i.e. some other failure condition would have had to coincide to create a wrong side failure. As it happened it was the investigation of a signal failure, loss of signal selection, that caused the faulty track relay to be discovered failing UP. As a result we had to change hundreds of relays on all lines, so many that SOS ran out of spare relays in short order and we found ourselves checking all the same type of relays in every relay room, IMR and trackside location then swapping suspect prime critical relays with checked okay relays within the same location. It was several weeks before we were able to replace the suspect relays with refurbished relays from SOS after first putting the swapped good relays back in their original circuits. Whoever ordered SOS to refurbish track relays with a different bearing material must have done so without reference to the Signal Engineers or the drawings of standard Westinghouse relays listing the approved materials used in their construction. Wrong side failures can of course be the result of faulty equipment which fails in an unexpected way (thus no electrical checking circuit or mechanical check exists as the problem has not been foreseen) or of incorrect wiring. A typical wrong side failure caused by incorrect wiring occurred at Wood Green circa 1978/9 on the first stage Picc East End resignalling changeover (removal of signal cabin, replaced by temporary relay room on the eastbound platform controlled from Arnos Grove cabin). The site was tested, recommissioned and trains were running following the Saturday night changeover. Some of us were still on site tidying up loose ends as there were problems with the then new electronic TD receiver. The first reverser came in to the platform, passengers alighted, doors closed, the shunt stick was OFF for the siding and the train then entered the siding and disappeared from the relay room diagram. The points were tracklocked reverse and Sunday morning trains began backing up in the tunnel waiting for the signalling to clear trains into the platform. The track over the points was F and the siding track was G but according to the diagram the siding was unoccupied and F track was down. All the work in the tunnels and cabling back to the relay room was done by night staff and day staff built the relay room. At some time prior to changeover night person or persons unknown had swapped the F & G track wiring at the fuse bay, evidenced by the fact that the allocations on the ticket stock temporary labels had been crossed out and switched. We thought the day staff had done it probably when they installed the track dropping boards but couldn't prove it and as our supervisor on nights was present he got the blame and was dropped basically to office tea boy after being admonished on site behind closed doors by the signalling tester. There are cases of potential wrong side failures caused by incorrect rewiring of changed relay tops etc going undiscovered for who knows how long only discovered by chance for instance when linemen were undergoing IRSE licensing and testing circuitry, one such problem was discovered at South Harrow where IIRC the NX was being switched by the signal selection of a signal instead of the BX. In another case a suspected wrong side failure, Hanger Lane Junction WM 20/21 wrong route clearing, was nothing of the sort. There was no doubt that the wrong route was set but legitimately so, the motorman having taken the route and then stopping over the points. We were on site PDQ, lifted relay tops, pulled fuses etc to preserve the evidence while the motorman was walked up and down the track by a train manager and asked to explain in detail what had occurred. We were certain that the signalling was not at fault although we had still to prove it and the motorman was adamant that the harbour lights were ON for his route. His job was on the line literally and his manager told him that he had to be 100% correct in his statement of 'fact'. In the end the motorman admitted that he had seen the harbour lights ON but was unsure if they were actually ON or if what he was seeing was the result of very strong summer sunlight that morning. The manager was happy to report a motorman's error, the motorman kept his job although I believe he was formally disciplined, we reinstated the signalling and it was checked and found to be 100% okay by night signalling maintenance at the end of traffic. I always found reported wrong side failures to be interesting but they were few and far between in my time as a signal lineman although I did many many failure investigations as a night TO. Hatton Cross route to T4 was suspect for a long time but it was never a wrong side failure, more an operational mode failure of the human kind i.e. not working the Heathrow desk at Earls Court correctly for last trains. |
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Post by dave1 on Jul 6, 2017 16:54:14 GMT
I think over the years there must have been many wrong side failures well reported as such but later found to be for a different reason. I bet that they don't really say exactly why though. I'm not sure what you are getting at here. All failures were/are thoroughly investigated to determine the exact cause and then take appropriate action. It is a fact that potential wrong side failures exist within signalling systems but they often go unnoticed until a particular set of circumstances highlights one. One such example was the failure of a track relay remaining mechanically stuck up as a result of the bearing material having been changed. It could have been disastrous as the relay had probably been stuck up more than once before it was discovered, in fact it might have been stuck up for weeks, the signal selection was such that the one relay stuck up could not on its own have caused a signalling failure i.e. some other failure condition would have had to coincide to create a wrong side failure. As it happened it was the investigation of a signal failure, loss of signal selection, that caused the faulty track relay to be discovered failing UP. As a result we had to change hundreds of relays on all lines, so many that SOS ran out of spare relays in short order and we found ourselves checking all the same type of relays in every relay room, IMR and trackside location then swapping suspect prime critical relays with checked okay relays within the same location. It was several weeks before we were able to replace the suspect relays with refurbished relays from SOS after first putting the swapped good relays back in their original circuits. Whoever ordered SOS to refurbish track relays with a different bearing material must have done so without reference to the Signal Engineers or the drawings of standard Westinghouse relays listing the approved materials used in their construction. Wrong side failures can of course be the result of faulty equipment which fails in an unexpected way (thus no electrical checking circuit or mechanical check exists as the problem has not been foreseen) or of incorrect wiring. A typical wrong side failure caused by incorrect wiring occurred at Wood Green circa 1978/9 on the first stage Picc East End resignalling changeover (removal of signal cabin, replaced by temporary relay room on the eastbound platform controlled from Arnos Grove cabin). The site was tested, recommissioned and trains were running following the Saturday night changeover. Some of us were still on site tidying up loose ends as there were problems with the then new electronic TD receiver. The first reverser came in to the platform, passengers alighted, doors closed, the shunt stick was OFF for the siding and the train then entered the siding and disappeared from the relay room diagram. The points were tracklocked reverse and Sunday morning trains began backing up in the tunnel waiting for the signalling to clear trains into the platform. The track over the points was F and the siding track was G but according to the diagram the siding was unoccupied and F track was down. All the work in the tunnels and cabling back to the relay room was done by night staff and day staff built the relay room. At some time prior to changeover night person or persons unknown had swapped the F & G track wiring at the fuse bay, evidenced by the fact that the allocations on the ticket stock temporary labels had been crossed out and switched. We thought the day staff had done it probably when they installed the track dropping boards but couldn't prove it and as our supervisor on nights was present he got the blame and was dropped basically to office tea boy after being admonished on site behind closed doors by the signalling tester. There are cases of potential wrong side failures caused by incorrect rewiring of changed relay tops etc going undiscovered for who knows how long only discovered by chance for instance when linemen were undergoing IRSE licensing and testing circuitry, one such problem was discovered at South Harrow where IIRC the NX was being switched by the signal selection of a signal instead of the BX. In another case a suspected wrong side failure, Hanger Lane Junction WM 20/21 wrong route clearing, was nothing of the sort. There was no doubt that the wrong route was set but legitimately so, the motorman having taken the route and then stopping over the points. We were on site PDQ, lifted relay tops, pulled fuses etc to preserve the evidence while the motorman was walked up and down the track by a train manager and asked to explain in detail what had occurred. We were certain that the signalling was not at fault although we had still to prove it and the motorman was adamant that the harbour lights were ON for his route. His job was on the line literally and his manager told him that he had to be 100% correct in his statement of 'fact'. In the end the motorman admitted that he had seen the harbour lights ON but was unsure if they were actually ON or if what he was seeing was the result of very strong summer sunlight that morning. The manager was happy to report a motorman's error, the motorman kept his job although I believe he was formally disciplined, we reinstated the signalling and it was checked and found to be 100% okay by night signalling maintenance at the end of traffic. I always found reported wrong side failures to be interesting but they were few and far between in my time as a signal lineman although I did many many failure investigations as a night TO. Hatton Cross route to T4 was suspect for a long time but it was never a wrong side failure, more an operational mode failure of the human kind i.e. not working the Heathrow desk at Earls Court correctly for last trains. Sorry I thought I made myself clear unless someone on the signal staff discovered a problem I would have said that either a driver or signalman would be the ones to report a fault. I have read a lot of accident reports both BR/LT where there was an issue with the signalling and it turned out to be nothing but there are some that had technical issues. Plaistow a few years back where a train was going eastbound and after leaving West Ham the driver noticed a train leave the bay road and cross over in front of the train although the signals were green. I seem to remember another one where a train left Earls Court westbound with a train following and the driver of the second train noticed that the starting signal remained green. The Wood Green incident you mention had they tested out? if so would it not have been found then and not after a train goes into the siding. |
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Post by railtechnician on Jul 7, 2017 16:18:35 GMT
Wrong side failures cannot be reported as such although they can be alleged, only a failure investigation by suitably qualified signal staff can determine if a failure is legitimate or illegitimate.
Your Plaistow incident is unclear, if a driver on cleared approach saw a train leave a bay road ahead and crossover but failed to crash into it why would that be reported as a failure. It sounds as though the departing train was beyond the overlap of the last clear signal for the approaching train. It is often the case that an approach signal has more than one overlap, a clear road ahead given a full speed overlap and a fouled road ahead given a controlled speed overlap. Without knowing the site and signalling in detail it is difficult to comment further except to say that every site is unique from a signalling point of view such that identical layouts may be signalled quite differently.
The Earls Court incident sounds odd given the complexity of the site, however, it is entirely possible for a signal to remain clear until a train has completely passed it. How soon after a train passes a signal it is replaced to danger depends upon the location of the replacing track blockjoint. One would usually expect a signal to be replaced within the first car or two passing it but in the case of high speed lines the replacing track blockjoint can be a long way ahead of the signal. The Met is a good example of this.
In the case of Wood Green the night staff tested everything in the tunnels back to the temporary relay room in accordance with the installation drawings. The day staff were responsible for fitting the track dropping boards prior to the changeover having tested all the internal relay room wiring in accordance with the installation drawings. However, there were no connections between the internal and external track circuits wiring in the relay room until the track dropping boards were installed. It was incumbent upon the day staff to ensure that the internal and external wiring matched at the fuse bay. It was no doubt when the track dropping board was fitted that the fuse bay F & G temporary labels were crossed out and reversed, assuming that the day staff when testing the dropping board connections apparently found F & G track internal wiring did not match the ticket strip labelling. This should have been reported to the day supervisor but if it was it was never mentioned to the night supervisor who would have checked the wiring all the way from the relay room to the track side locations. My recollection is that F & G track circuits were in the same 7 pair concentric cable to a terminating Westinghouse location case at the entrance to the siding on the eastbound road and then one pair cables went to each track circuit, the F & G track relays being in the temporary relay room. On the changeover I worked the track dropping board for the signalling tester, a job I did on a number of changeovers during my two years on signal New Works. I clearly recall the route to the siding being tested and being asked to drop F track and then G track. The tester said 'I said drop G' and I replied that I had dropped G, clearly there was an issue but I was a relative newbie wireman and tight discipline of the time meant that wiremen did not interrupt supervisors and managers without permission and nobody else in the room noticed anything worth reporting including our chief supervisor. Whatever the tester saw or didn't see he carried on testing without seeing a problem which he should have seen. There was no query or investigation until the first reverser took the route to the siding and our chief supervisor went down the tunnel to clip and scotch the points normal in order to get the backed up trains moving.
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Post by dave1 on Jul 7, 2017 18:55:52 GMT
Wrong side failures cannot be reported as such although they can be alleged, only a failure investigation by suitably qualified signal staff can determine if a failure is legitimate or illegitimate. Your Plaistow incident is unclear, if a driver on cleared approach saw a train leave a bay road ahead and crossover but failed to crash into it why would that be reported as a failure. It sounds as though the departing train was beyond the overlap of the last clear signal for the approaching train. It is often the case that an approach signal has more than one overlap, a clear road ahead given a full speed overlap and a fouled road ahead given a controlled speed overlap. Without knowing the site and signalling in detail it is difficult to comment further except to say that every site is unique from a signalling point of view such that identical layouts may be signalled quite differently. The Earls Court incident sounds odd given the complexity of the site, however, it is entirely possible for a signal to remain clear until a train has completely passed it. How soon after a train passes a signal it is replaced to danger depends upon the location of the replacing track blockjoint. One would usually expect a signal to be replaced within the first car or two passing it but in the case of high speed lines the replacing track blockjoint can be a long way ahead of the signal. The Met is a good example of this. In the case of Wood Green the night staff tested everything in the tunnels back to the temporary relay room in accordance with the installation drawings. The day staff were responsible for fitting the track dropping boards prior to the changeover having tested all the internal relay room wiring in accordance with the installation drawings. However, there were no connections between the internal and external track circuits wiring in the relay room until the track dropping boards were installed. It was incumbent upon the day staff to ensure that the internal and external wiring matched at the fuse bay. It was no doubt when the track dropping board was fitted that the fuse bay F & G temporary labels were crossed out and reversed, assuming that the day staff when testing the dropping board connections apparently found F & G track internal wiring did not match the ticket strip labelling. This should have been reported to the day supervisor but if it was it was never mentioned to the night supervisor who would have checked the wiring all the way from the relay room to the track side locations. My recollection is that F & G track circuits were in the same 7 pair concentric cable to a terminating Westinghouse location case at the entrance to the siding on the eastbound road and then one pair cables went to each track circuit, the F & G track relays being in the temporary relay room. On the changeover I worked the track dropping board for the signalling tester, a job I did on a number of changeovers during my two years on signal New Works. I clearly recall the route to the siding being tested and being asked to drop F track and then G track. The tester said 'I said drop G' and I replied that I had dropped G, clearly there was an issue but I was a relative newbie wireman and tight discipline of the time meant that wiremen did not interrupt supervisors and managers without permission and nobody else in the room noticed anything worth reporting including our chief supervisor. Whatever the tester saw or didn't see he carried on testing without seeing a problem which he should have seen. There was no query or investigation until the first reverser took the route to the siding and our chief supervisor went down the tunnel to clip and scotch the points normal in order to get the backed up trains moving. I am sure that a driver or signalman would not say I have a wrong side failure but those who were investigating would be the ones to identify unless there was a cover up and I'm not saying that has ever happened. If two trains were involved in a collision then there would be investigations to ascertain the cause. The Plaistow incident the signals were clear into the eastbound platform but a train left the bay road going westbound!! I think it was something to do with new works being done. I don't think that would have been reported as a failure. I forgot to say Earls Court was on the Piccadilly line so not a complex site. The Wood Green site would have been signed off to say all was working correctly? |
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Post by Nortube on Jul 8, 2017 11:44:39 GMT
re Plaistow:
I've heard of this before, but I can't remember when it was. I don't know the current signal arrangements, but looking at the details of 20 years ago, there were three controlled signals before the EB Plaistow platform - two before the E/W crossover (7 points) - FC11A and FC11B - and one between 7 points and the crossover from the bay platform (6 points) - FC11C/8B.
FC11A protects the E/W crossover and will not clear if the crossover is reversed
FC11B is approach controlled and can clear approximately 200 feet after the first pair of wheels of the approaching train has passed the West Ham EB starter. FC11B will not clear if 7 points are Reversed. 6 points can be Normal (EB platform) or Reverse (bay road).
F11C/8B is a dual-controlled two aspect signal:
8B – comes into operation when a train is reversing W-E over 7 crossover to either the EB or bay platform
11C – comes into operation when a train from West Ham is routed to either the EB platform or bay. When the route is set for the bay, the signal becomes speed controlled (4.5 second delay after passing FC11B before the signal will clear with a route indicator). This means that an approaching train has to be at around 20mph or less by the time it arrives at the signal. Any faster and the signal will not have cleared and the train would get tripped.
From the above, it can be seen (as expected) that if the route is set for a train to depart east from the bay, 7 and 6 points will be reversed, a train approaching from West Ham should see three red signals between West Ham and the EB platform at Plaistow. If the driver of an approaching train could see any of these signals green when a train was crossing over in front of them, then something was seriously wrong.
Many years ago at Morden, before the new Garth House building, and crews used to wait around on the bridge for their train, myself and others saw all NB starters briefly go from Red to Green then back to Red. Nobody knows exactly what happened and I don’t even know if it was reported at the time. As the local AET showed me on some of the bookwiring when I spoke to him, it would be impossible to happen because of all the various interlockings etc. However it did!. If it had been only me saw it, I might have thought it was my imagination, but the fact that two or three other drivers noticed it as well at least proved that it happened. People were in the IMR at the time, so I assume that it was something related to what they were doing or touched. I wondered if in fact it had been a strobe where the three signals individually went from red to green to red one after another rather than all at once, but too fast for the eye to see as individual actions(like a multiplexed digital display), but couldn’t see how that would happen either.
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Post by Nortube on Jul 8, 2017 15:36:40 GMT
Then there was the District line collision at Charing Cross on 17 May 1938 - wrong side failure due to human error: [ Click here ] |
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Post by railtechnician on Jul 9, 2017 9:53:19 GMT
re Plaistow: I've heard of this before, but I can't remember when it was. I don't know the current signal arrangements, but looking at the details of 20 years ago, there were three controlled signals before the EB Plaistow platform - two before the E/W crossover (7 points) - FC11A and FC11B - and one between 7 points and the crossover from the bay platform (8 points) - FC11C/8B. FC11A protects the E/W crossover and will not clear if the crossover is reversed FC11B is approach controlled and can clear approximately 200 feet after the first pair of wheels of the approaching train has passed the West Ham EB starter. FC11B will not clear if 7 points are Reversed. 8 points can be Normal (EB platform) or Reverse (bay road). F11C/8B is a dual-controlled two aspect signal: 8B – comes into operation when a train is reversing W-E over 7 crossover to either the EB or bay platform 11C – comes into operation when a train from West Ham is routed to either the EB platform or bay. When the route is set for the bay, the signal becomes speed controlled (4.5 second delay after passing FC11B before the signal will clear with a route indicator). This means that an approaching train has to be at around 20mph or less by the time it arrives at the signal. Any faster and the signal will not have cleared and the train would get tripped. From the above, it can be seen (as expected) that if the route is set for a train to depart east from the bay, 7 and 8 points will be reversed, a train approaching from West Ham should see three red signals between West Ham and the EB platform at Plaistow. If the driver of an approaching train could see any of these signals green when a train was crossing over in front of them, then something was seriously wrong. Many years ago at Morden, before the new Garth House building, and crews used to wait around on the bridge for their train, myself and others saw all NB starters briefly go from Red to Green then back to Red. Nobody knows exactly what happened and I don’t even know if it was reported at the time. As the local AET showed me on some of the bookwiring when I spoke to him, it would be impossible to happen because of all the various interlockings etc. However it did!. If it had been only me saw it, I might have thought it was my imagination, but the fact that two or three other drivers noticed it as well at least proved that it happened. People were in the IMR at the time, so I assume that it was something related to what they were doing or touched. I wondered if in fact it had been a strobe where the three signals individually went from red to green to red one after another rather than all at once, but too fast for the eye to see as individual actions(like a multiplexed digital display), but couldn’t see how that would happen either. As I always say, one can only speculate about the whys and wherefores of any given signalling situation until one has both the signalling diagram and the bookwiring in sight. Something in your signalling description must be wrong, both signal and points cannot be designated 8, points and signals have to be on different levers. Despite this I can see where you are coming from and agree that a train approaching Plaistow E/B on the main should see red signals. That said, without seeing the bookwiring and diagram it is impossible to know if any legitimate (although very unlikely) circumstance could lead to FC11A being green with a train ahead reversing E-W from the bay road. We don't know how far the cab of the approaching train was from FC11A but clearly not that close or the motorman would probably have passed it. Such leads to a simple possibility i.e. the motorman did not see FC11A red but may not have seen a green either. It is a fact that in some circumstances unlit signals are seen as lit aspects, it could simply have been a blown red light and an apparently lit green assuming the motorman was only just within sighting distance, the green 'illuminated' by reflected sunlight! No doubt a failure investigation report was filed at the time, assuming the 'incident' was reported but we will probably never know unless it was investigated by the railway inspectorate. When it comes to failures absolutely nothing is impossible, no matter how unlikely the possibility. Just because reading the bookwiring suggests that it is an electrical impossibility for any given failure to occur does not make it so, nothing can be ruled out in an investigation and while we like to believe that the drawings are 100% we must never assume it to be so. Signalling asset and cabling wear and tear can lead to strange and unexpected results, sometimes not as a direct result of failure but at times a result of fault localisation and rectification. It should not be so but human error is always a possibility in failure creation or potential for such. |
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Post by Nortube on Jul 12, 2017 9:06:02 GMT
Oops! the crossover points to / from the bay should have been 6 points (6a and 6b) not 8. I've edited the original post
I forgot to mention that FC11B is almost at the E-W crossover, FC11A is about 540 feet before that.
FC11C/8B is in the short gap between 7 and 8 crossover
What I'm describing is the signalling arrangement prior to the addition of the double-ended Plaistow loop, which ends just west of the bridge that carries all of north London's sewage over the tracks, so there would have been be changes to the signal layout ex West Ham, even if it was just to make West Ham EB starter a controlled signal.
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Post by railtechnician on Jul 12, 2017 12:41:07 GMT
The report into the Charing Cross (Embankment) collision is interesting and highlights many issues. I am surprised to see so few recommendations as a result of the incident. Clearly it took further incidents to make signalling of the time more akin to what it became before I joined LT. The spread of blame is also interesting from a time when discipline was reputed to be high, certainly had the event occurred 40 years later those blamed would no doubt have been dropped from a great height, the wireman would have been lucky to keep his job, the chief signal lineman would have been back in the gang as a wireman for at least 6 months or a year before being allowed to climb the ranks again and the stigma of being dropped would have stuck with him for the rest of his career. I knew of one or two AETs in the 1970s who were so dropped, indeed I was on a comms chargehand course with one in 1981, we were both senior wiremen then, I'm not sure he ever made it back to AET. I expect the penalties for the traffic staff would've been similarly severe although manager grades seemed to get kicked sideways as was the case with middle managers in the signal department after making mistakes on signalling changeovers.
In the early noughties I was appalled to attend a failure at Heathrow which was affecting first trains only to discover two signalling shift supervisors laughing and joking in the IMR with Q relays all over the floor, they were on overtime to change relays and had lost track of time. They were embarassed but unworried as they reckoned the NAKS value (what the delay would cost financially) for first trains being delayed was low on a Sunday morning and all they would get was a slapped wrist, that turned out to be so. I am well aware that if they had caught me in a similar position I would have been severely disciplined.
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