|
|
Post by jamesb on Aug 6, 2015 20:56:15 GMT
The Victoria line uses Distance To Go-Radio (DTG-R), supplied by "Invensys" (which, I believe, is what Westinghouse became). I believe - according to a comment on London Reconnections - that they were actually Metronet's original choice for the SSR. But, in any case, I'm not sure whether Invensys even put in a bid this time - nor even if they're still supplying DTG-R systems. By the way I absolutely cannot agree with you. Victoria line trains stop like they've hit a brick wall everywhere, accelerate very hard and transition between accelerating and braking with all the smoothness of the Giant's Causeway. So uncomfortable. Yes but I like the hard acceleration it gives the impression I'm getting from A to B more quickly! whether that is true or not i'm not sure... you feel the power of the trains more |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 6, 2015 21:08:48 GMT
Thales were the only bidder this time I believe.
|
|
|
|
Post by domh245 on Aug 6, 2015 21:10:33 GMT
Correct again tut. At the point of metronet sealing the deal, it was westinghouse, who then became invensys. In 2013 they were sold to Siemens and is now known as Siemens Rail Automation. And I do agree with jamesb, the DTG-R system is superior. I've made well known my feelings on the S40 binary driving style, and other members have made known their opinions on it and it's shortcomings. But then again they do appeared to have made it a bit smoother of late. Also, I'm fairly sure that Seltrac were the only bidders for this 3rd attempt at resignalling, seeing as once Westinghouse/Invenysys/Siemens were paid off, and Bombardier were paid off, and I don't think that there are many other rail automation systems left at this point! |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 6, 2015 21:16:54 GMT
Oh don't mistake me. I have no love for S40 and TBTC, although we are getting some kind of S40+ on the SSR aren't we? I didn't think S40 was up to the job. Not that I expect the improvements to be of ride quality. Actually, the funny thing is, even though Jubilee and Northern line trains spend an absolute age slowing down, they still manage to stop with a jerk - it's quite remarkable, really. I'd describe the ATO on the Jubilee and Northern as childish in its driving style. *Go*. *Stop*. *Go*. I'd describe ATO on the Victoria as downright violent. I hate having to stand on the Vic and I dread to think what it must be like in rush hour.
|
|
North End
Beneath Newington Causeway
Posts: 1,769
|
Post by North End on Aug 6, 2015 21:33:44 GMT
Oh don't mistake me. I have no love for S40 and TBTC, although we are getting some kind of S40+ on the SSR aren't we? I didn't think S40 was up to the job. Not that I expect the improvements to be of ride quality. Actually, the funny thing is, even though Jubilee and Northern line trains spend an absolute age slowing down, they still manage to stop with a jerk - it's quite remarkable, really. I'd describe the ATO on the Jubilee and Northern as childish in its driving style. *Go*. *Stop*. *Go*. I'd describe ATO on the Victoria as downright violent. I hate having to stand on the Vic and I dread to think what it must be like in rush hour. The driving style, bad as it may be, is the least of Seltrac's failings. Issues and glitches by the dozen, every 'fix' seems to create a new problem, and a "take it or lump it" attitude from the supplier. It's sad that LU have allowed things to reach a situation where Thales appear to be the only realistic contractor. |
|
|
|
Post by domh245 on Aug 6, 2015 21:37:05 GMT
It will still be S40, but just with the (presumably VOBC software) based upgrades from the Northern line as implied by North End hereI don't mind the victoria line's kamikaze style braking - I don't find it very noticable, and during rush hours, it's not too bad, although those human-sized cushions help! Although experience of riding trams whilst not being able to reach the strap hangers and having to lean into the movements may have helped |
|
North End
Beneath Newington Causeway
Posts: 1,769
|
Post by North End on Aug 6, 2015 21:43:06 GMT
The Victoria line uses Distance To Go-Radio (DTG-R), supplied by "Invensys" (which, I believe, is what Westinghouse became). I believe - according to a comment on London Reconnections - that they were actually Metronet's original choice for the SSR. But, in any case, I'm not sure whether Invensys even put in a bid this time - nor even if they're still supplying DTG-R systems. By the way I absolutely cannot agree with you. Victoria line trains stop like they've hit a brick wall everywhere, accelerate very hard and transition between accelerating and braking with all the smoothness of the Giant's Causeway. So uncomfortable. I don't entirely agree with this. I agree that the Victoria Line trains stop with a jolt (as do the Jubilee and Northern Lines), but the normal driving style is smooth. The trains recognise the line characteristics, and when running early the trains coast. So, with a clear run, for most sections you can expect the train to motor up to maximum permitted speed, coast (either later or earlier depending on late running), and then brake to a stand. By contact, the Seltrac way of driving is simply that the train is given a speeed and the train tries to maintain that speed. If running early, the train will be given a lower maximum permitted speed for the entire section. So even if running downhill, the train will brake down to that speed rather than coast. The result is constant on/off of motors and braking. By a similar token, the Northern Line also has a horrible characteristic that when slowing down for a speed restriction, the train will over-brake by sometimes up to 5 mph, sit too slow for a few seconds, then motor back up to the speed it should have achieved -- wasted time, and uncomfortable for the passenger. The only time you get the motor/brake effect on the Victoria Line is when closely following another train, but the benefit in this situation can be appreciated seeing the Victoria Line's daily achievement of 34tph. Platform re-occupation with Seltrac is nowhere near as impressive. At Stockwell southbound, always one of the biggest pinch-points on the Northern Line during the evening peak, with a train sitting in the platform, the following train sits still for *ages*, then motors into the platform in one go. Granted the following train will be marginally closer to the platform than under the old signalling, but it waits *way* longer than under signals before moving. The same happens at loads of locations across the Northern Line - the glossy publicity of trains smoothly following each other is complete rubbish. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 6, 2015 21:48:11 GMT
It will still be S40, but just with the (presumably VOBC software) based upgrades from the Northern line as implied by North End hereI don't mind the victoria line's kamikaze style braking - I don't find it very noticable, and during rush hours, it's not too bad, although those human-sized cushions help! Although experience of riding trams whilst not being able to reach the strap hangers and having to lean into the movements may have helped Well we know one big difference is that the SSR system is set to use radio, rather than the inductive loops. An older London Reconnections article cites a press release as saying: Accompanying the quote with the commentary: Exactly what that means is not 100% clear, but I think it'll surely have to be more than just the latest, most upgraded version of what's on the Northern and Jubilee. |
|
North End
Beneath Newington Causeway
Posts: 1,769
|
Post by North End on Aug 6, 2015 21:56:36 GMT
It will still be S40, but just with the (presumably VOBC software) based upgrades from the Northern line as implied by North End hereI don't mind the victoria line's kamikaze style braking - I don't find it very noticable, and during rush hours, it's not too bad, although those human-sized cushions help! Although experience of riding trams whilst not being able to reach the strap hangers and having to lean into the movements may have helped Well we know one big difference is that the SSR system is set to use radio, rather than the inductive loops. An older London Reconnections article cites a press release as saying: Accompanying the quote with the commentary: Exactly what that means is not 100% clear, but I think it'll surely have to be more than just the latest, most upgraded version of what's on the Northern and Jubilee. They need to find a solution to the issue of braking rates in the open. The system offers the ability to vary brake rates, for example during the wet. The difficulty is devising a reliable way of predicting when you need to alter the brake rate. To be fair, no ATO system is immune from this. The Central Line runs rail adhesion trains during the autumn, and basically accepts that there will occasionally be station overruns. The big flaw with Seltrac is that a sliding trains cannot accurately reports its speed/position, therefore the system is designed to halt the VOBCs, sending the train non-communicating, and meaning it has to be re-entered into the system, which requires driving in RM to the next loop boundary, wherever that may be. PM driving does not help, as the driver has no way of predicting when the system is going to request a change in speed, as under the current setup the TOD will only give the standard 3 seconds warning before dropping down (I can't see any technical reason why this couldn't be extended, but then you'd have a problem that drivers would be braking early in dry conditions!). So on the Jubilee and Northern Lines the brake rates are set to gentle rates in open sections. Imagine the effect on journey times for the whole of the SSR! |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 6, 2015 21:58:10 GMT
The Victoria line uses Distance To Go-Radio (DTG-R), supplied by "Invensys" (which, I believe, is what Westinghouse became). I believe - according to a comment on London Reconnections - that they were actually Metronet's original choice for the SSR. But, in any case, I'm not sure whether Invensys even put in a bid this time - nor even if they're still supplying DTG-R systems. By the way I absolutely cannot agree with you. Victoria line trains stop like they've hit a brick wall everywhere, accelerate very hard and transition between accelerating and braking with all the smoothness of the Giant's Causeway. So uncomfortable. I don't entirely agree with this. I agree that the Victoria Line trains stop with a jolt (as do the Jubilee and Northern Lines), but the normal driving style is smooth. The trains recognise the line characteristics, and when running early the trains coast. So, with a clear run, for most sections you can expect the train to motor up to maximum permitted speed, coast (either later or earlier depending on late running), and then brake to a stand. By contact, the Seltrac way of driving is simply that the train is given a speeed and the train tries to maintain that speed. If running early, the train will be given a lower maximum permitted speed for the entire section. So even if running downhill, the train will brake down to that speed rather than coast. The result is constant on/off of motors and braking. By a similar token, the Northern Line also has a horrible characteristic that when slowing down for a speed restriction, the train will over-brake by sometimes up to 5 mph, sit too slow for a few seconds, then motor back up to the speed it should have achieved -- wasted time, and uncomfortable for the passenger. The only time you get the motor/brake effect on the Victoria Line is when closely following another train, but the benefit in this situation can be appreciated seeing the Victoria Line's daily achievement of 34tph. Platform re-occupation with Seltrac is nowhere near as impressive. At Stockwell southbound, always one of the biggest pinch-points on the Northern Line during the evening peak, with a train sitting in the platform, the following train sits still for *ages*, then motors into the platform in one go. Granted the following train will be marginally closer to the platform than under the old signalling, but it waits *way* longer than under signals before moving. The same happens at loads of locations across the Northern Line - the glossy publicity of trains smoothly following each other is complete rubbish. Ah, I have absolutely no dispute on the motor/brake front, I completely agree and I think it sucks. Also - even just the noise of it is maddening. Well, in terms of keeping speed, yes. But if a Vic line train needs to transition from braking to motoring, I feel it does it quite uncomfortably. And since they slow down quickly and accelerate hard, the effect is quite pronounced. For me personally, I feel jolly tossed around on the Vic line, I don't feel that any thought is spared for gentleness or comfort. The 1992s for instance (for all the Central line's ATO faults), will brake constantly (but hard) towards the stopping mark, and then ease off the brakes in the final few moments for a much softer stop. Whereas the Vic will come in with the motors slowing it down (regenerative braking) and then put the anchors on right at the end. And it feels like a dropped handle. And then they pull away at full whack. And, of course, it's the same when it comes to a stop at a red signal (or equivalent). I read somewhere that sensitive edge was introduced on the 2009 stock because the weight of the doors was enough to pull them open under braking. I know how the poor doors feel! |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 7, 2015 7:48:43 GMT
I've said this before but I will try again. Seltrac is quite capable of being specified with coasting - the issue was that it was not incentivised in the PPP for Tube Lines to deliver it. Applying coasting results in a slight reduction in performance and therefore run times (it must do if the train is not running as fast as possible all of the time). That reduction (in PPP days and even now) must be made up another way; either by more trains, faster trains, less dwell times or a lower tph or a mix of all of them. The Victoria line had the benefit of specifying the right number of new trains to meet the required journey times whereas the Northern had a fixed number of trains. The original Jubilee proposal was to buy 10 new trains but Tube Lines went for 4 in the end as they calculated they could still hit the PPP requirements with that number of trains and performance pushed to the maximum.
SSR has exactly the same underlying signalling logic as the Northern albeit with radio rather than loop and a number of changes to meet SSR specific needs such as the inteface with Chiltern, Network Rail and the Piccadilly line. There is no real change to the core functionality in the non-interworking areas such as the Circle line. Coasting will be delivered for SSR towards the end of the project and it will also be introduced to the Northern line under NLU2. In both case probably for use outside of the peak.
Brake rates on any Seltrac line only need to be set to gentle in slippery conditions such as ice, drizzle or leaf fall. There is no need for them to be left at that rate all of the time (but I know generally they are .... which is frustrating). There is a reasonably reliable prediction method completely separate from Seltrac which I think is used by all automatic lines that have open sections.
|
|
|
|
Post by spsmiler on Aug 7, 2015 22:33:04 GMT
Judging by the comments about the Jubilee, Northern and Victoria Lines, could it be that despite its age (and naff rolling stock) the Central Line's system offers the smoothest ride and best performance?
As someone who uses that line the most I admit to being biased.
re: slow gentle acceleration and braking, the Overground fits that bill horribly. Its infuriating... surely if the trains were driven with gusto overall journey times could be reduced...
Simon
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Aug 7, 2015 22:43:09 GMT
I like the Central's system when it's working, which is not really often enough. But if it's a dry day and the sun is out and everything comes together and you've got a good tail wind, it surely offers the nicest ride in my personal opinion. Poor in the wet, though, and prone to serious unreliability. It's also not exactly the height of signalling technology, so it probably can't deliver as much. It also suffers from driving at maximum speed until the last possible moment and then braking as hard and late as it reasonably can to 'make the most out of the railway' - but it seems to manage it with a lot more finesse, in my opinion. Very harsh on the motors, though, I've heard. It also suffers from a tendency to hit the target speed and, well, I describe it as bouncing. Brake ... brake ... brake ... Try Stratford to Mile End on the west, until around the Old Ford escape shaft.
Had a silky smooth journey home, in what I'm 99% sure was Coded, all the way from Holborn to Hainault. Beautiful (although a slight tendency to bounce, here, too). Mind you, I think the overloads dropped out at Leyton. AUX SET REQ.
PS: When I say 'like'. I obviously don't mean...
|
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,773
|
Post by Chris M on Aug 7, 2015 22:53:56 GMT
It isn't just the Central with unreliability. The last journey I did on the Jubilee the train arrived into Canary Wharf eastbound and pulled up about 1½ cars short, the t/op then pulled forward to the stopping mark but it seemingly refused to talk to the PEDs.
|
|
|
|
Post by marri260 on Aug 8, 2015 6:44:46 GMT
Has probably been pointed out before but the S stock are fitted with sanding equipment which I guess could potentially allow a slightly heavier braking rate in the open under ATO?
|
|
|
|
Post by domh245 on Oct 20, 2015 16:24:21 GMT
|
|
|
|
Post by christopher125 on Oct 24, 2015 0:59:47 GMT
"Chiltern line drivers will continue to see either a red, yellow or green aspect and will drive accordingly. Their trains will retain trip cock apparatus to trigger any signal overruns"
Why not install AWS/TPWS and do away with tripcocks entirely? Given the restraints it places on rolling stock it seems such an obvious thing to do, especially as the Wimbledon branch will surely need to be signalled in this way.
|
|
|
|
Post by melikepie on Oct 24, 2015 1:05:18 GMT
Last time I checked, Chiltern Trains did not travel down the Wimbledon branch
|
|
|
|
Post by domh245 on Oct 24, 2015 9:42:02 GMT
"Chiltern line drivers will continue to see either a red, yellow or green aspect and will drive accordingly. Their trains will retain trip cock apparatus to trigger any signal overruns" Why not install AWS/TPWS and do away with tripcocks entirely? Given the restraints it places on rolling stock it seems such an obvious thing to do, especially as the Wimbledon branch will surely need to be signalled in this way. I suspect it is to do with the fact that LU are the track owners on the Chiltern line, whilst NR own the Wimbledon and Richmond Branches. Essentially, It makes sense for the Wimbledon and Richmond Branches to be kitted out with TPWS because that is the standard form of SPAD mitigation used by that infrastructure owner. LU's standard system is the tripcock so that is what is being used. But I agree, it would have been a good time to try and get rid of that non-standard interface. There is a difference in the way that the systems are interfacing however. On the District, the S40 system is overlaying onto the NR block signals, so it will still effectively be driving signal to signal, but now the train will be able to drive itself. The signals are still the primary form of signalling, the S40 just takes information from that and delivers it to the train eg: Is signal clear (Yes/No) If Y - set movement authority to next signal If N - return to top Repeat. The Met will have the S40 system as the primary signalling system, the colour lights will be underlayed. S40 will generate movements for trains, and the signals will show Red if the movement authority ends within the overlap + train length, blue if the MA is greater than the overlap and separation distance (~100m), and green/yellow (as applicable on next signal) if the MA reaches the next signal eg: Is a train within overlap of signal - Y set Red, N continue Is a train within distance to next Colour signal - Y set Red, N set blue & continue Is colour light section clear of trains - Y set yellow/green/blue (depending on circumstances), N set Red NB, blue lights only shown for LU stock, which I am assuming will work by reading the headcodes in the track berths, if it is an NR style headcode, blue won't be shown, if it is LU style headcode, blue shown (if MA is available) Or at least, that is my understanding of it! |
|
|
|
Post by Dstock7080 on Oct 24, 2015 10:38:38 GMT
I suspect it is to do with the fact that LU are the track owners on the Chiltern line, whilst NR own the Wimbledon and Richmond Branches. Essentially, It makes sense for the Wimbledon and Richmond Branches to be kitted out with TPWS because that is the standard form of SPAD mitigation used by that infrastructure owner. LU own the infrastructure on the Wimbledon branch, bridges and other structures are numbered into the LU standard system. Signalling, power control and Rule & Regulations currently remain with NR. TPWS is already provided on the Wimbledon branch for NR trains. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 24, 2015 10:40:54 GMT
"Chiltern line drivers will continue to see either a red, yellow or green aspect and will drive accordingly. Their trains will retain trip cock apparatus to trigger any signal overruns" Why not install AWS/TPWS and do away with tripcocks entirely? Given the restraints it places on rolling stock it seems such an obvious thing to do, especially as the Wimbledon branch will surely need to be signalled in this way. I suspect it is to do with the fact that LU are the track owners on the Chiltern line, whilst NR own the Wimbledon and Richmond Branches. Essentially, It makes sense for the Wimbledon and Richmond Branches to be kitted out with TPWS because that is the standard form of SPAD mitigation used by that infrastructure owner. LU's standard system is the tripcock so that is what is being used. But I agree, it would have been a good time to try and get rid of that non-standard interface. There is a difference in the way that the systems are interfacing however. On the District, the S40 system is overlaying onto the NR block signals, so it will still effectively be driving signal to signal, but now the train will be able to drive itself. The signals are still the primary form of signalling, the S40 just takes information from that and delivers it to the train eg: Is signal clear (Yes/No) If Y - set movement authority to next signal If N - return to top Repeat. The Met will have the S40 system as the primary signalling system, the colour lights will be underlayed. S40 will generate movements for trains, and the signals will show Red if the movement authority ends within the overlap + train length, blue if the MA is greater than the overlap and separation distance (~100m), and green/yellow (as applicable on next signal) if the MA reaches the next signal eg: Is a train within overlap of signal - Y set Red, N continue Is a train within distance to next Colour signal - Y set Red, N set blue & continue Is colour light section clear of trains - Y set yellow/green/blue (depending on circumstances), N set Red NB, blue lights only shown for LU stock, which I am assuming will work by reading the headcodes in the track berths, if it is an NR style headcode, blue won't be shown, if it is LU style headcode, blue shown (if MA is available) Or at least, that is my understanding of it! Not quite LU own the Wimbledon branch but due to NR trains running over it the signalling must reflect this hence why its to NR standards not LU's. NR maintain and fix faults under contract but we still do the maintenance and fault finding on the Dot Matrix and CSDE and Air Main. P-Way also comes under LU but again its done under contract to NR I believe its Balfour Beaty On the Richmond branch NR own the lot we do not do anything past GB1 signal on the westbound and DD1 track (just underneath Chiswick Park) on the eastbound. Barons Court going west will have to keep colour light signals and trainstops due to the Piccadilly Line they are not going to remove the junctions as previously thought when the CityFlo system was knocking around. Going back to the Met Line only the fast lines past Harrow on the Hill and then past Watford South Junction will retain colour light signals as mentioned for the Chiltern's. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 24, 2015 22:56:05 GMT
The Met will have the S40 system as the primary signalling system, the colour lights will be underlayed. S40 will generate movements for trains, and the signals will show Red if the movement authority ends within the overlap + train length, blue if the MA is greater than the overlap and separation distance (~100m), and green/yellow (as applicable on next signal) if the MA reaches the next signal eg: Is a train within overlap of signal - Y set Red, N continue Is a train within distance to next Colour signal - Y set Red, N set blue & continue Is colour light section clear of trains - Y set yellow/green/blue (depending on circumstances), N set Red NB, blue lights only shown for LU stock, which I am assuming will work by reading the headcodes in the track berths, if it is an NR style headcode, blue won't be shown, if it is LU style headcode, blue shown (if MA is available) Or at least, that is my understanding of it! If I've understood you correctly, I think my interpretation of the information in the link you provided is a little different. The system, it seems, will indeed use train descriptions to differentiate between LU and NR stock. What the signal will show will, as you rightly say, depend on which train is approaching. Let's take the example of signals A852 and A854 - the first two automatic signals out of Harrow-on-the-Hill on the northbound main. Remember that the overlap that extends beyond A852 applies to the preceding signal (JB7) and that the overlap beyond A854 applies to A852. (N.B. whether signals, their numbers and their placement will change, I do not know; but let's use the current state of play for an example). If an NR train is approaching A852 and there is a train between A852 and A854, or in the overlap beyond A854, the signal will be red. If not, it will be yellow, or green. It will be yellow if there is a train between A854 and the next signal (A858), or if there is a train in the overlap beyond the next signal (A858), and green otherwise. If an LU train is approaching A852 I guess it will be blue under all normal circumstances, as the link says. We might presume it would be red if the movement authority ends at signal A852, but if this is a true underlay, the movement authority should be constantly updated and not forced to artificially end at fixed signals. The system is designed to allow a following distance of around 100 m, with the movement authorities changing to reflect that. (I don't believe it's exactly 100 m, but let's work with that for the sake of discussion.) So unless a train happens to stop exactly 100 m (or whatever the closest following distance is set at) from A852, the movement authority of the following train (if this is a true underlay) will almost never end exactly at A852. If a train happens to be within 100 m of A852, say 90 m from it, then the movement authority of the following train should end 10 m in rear of A852, making a red aspect on A852 unhelpful at best, because although the following train isn't allowed past A852, it isn't actually allowed to approach it either, it should stop 10 m before it. Instead, a blue aspect - essentially meaning 'obey in cab signalling' - is surely less misleading. Of course, colour light signals associated with TBTC can show red, I think the Jubilee has them. But I thought these behaved like semi-autos, where it makes sense for them to be a fixed limit of movement authority. So, in other words, my interpretation of the information in the link is that the system must determine what type of train is approaching. If LU, it will show blue. If NR, it will show red if there is a train between this signal and the next one, or in the overlap of this signal (which extends beyond the next signal). It will show yellow if not, but there is a train between the next signal and the one after, or in the overlap of the next signal. It will show green otherwise. Obviously if there's a train in the overlap extending beyond this signal, no NR train will be approaching, since it will necessarily be held at the preceding signal (to which it applies), until the overlap is clear. An LU train may be approaching, in which case, I assume, it will show blue. The movement authority will reflect the exact position of the next train and the movement authority may end in rear of, in advance of, or even precisely at this signal (although the latter is surely unlikely if this is a true underlay). Of course, I may be completely wrong about this, the link was a little unsatisfying. But this is the interpretation I have of: And It would seem a bizarre interpretation of 'underlay' if movement authorities for LU trains were related to fixed, lineside signals. Additionally, if lineside signals do indeed display red aspects for LU trains all the while a train is within 100 m of them (and, hence, no other train would be permitted to proceed past them), this - I think - would be an interesting decision. If anybody has anything more concrete, or any clarifications, at this early stage - I for one would welcome them  |
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,773
|
Post by Chris M on Oct 24, 2015 23:07:50 GMT
An NR train should never see blue, but if it did (I'm sure there must be at least one failure mode where it can happen) I guess the NR train will treat it as a red signal and contact the signaller to obtain a movement authority?
|
|
rincew1nd
Administrator
Junior Under-wizzard of quiz
Posts: 10,286 
|
Post by rincew1nd on Oct 25, 2015 1:17:39 GMT
Perhaps it's interesting to note that when TPWS is overlaid on RETB lines a flashing blue aspect was/is used to show that the TPWS loops at the STOP boards were inactive as a Radio Electric Token had been issued for the section in advance.
|
|
|
|
Post by domh245 on Oct 25, 2015 9:59:37 GMT
Good points tut, I was never particularly clued up about signalling anyway! In hindsight, 11AM on a saturday morning probably isn't the best time for students to be writing lost posts on internet forums! |
|
|
|
Post by 100andthirty on Oct 25, 2015 10:09:16 GMT
I suspect it is to do with the fact that LU are the track owners on the Chiltern line, whilst NR own the Wimbledon and Richmond Branches. Essentially, It makes sense for the Wimbledon and Richmond Branches to be kitted out with TPWS because that is the standard form of SPAD mitigation used by that infrastructure owner. LU own the infrastructure on the Wimbledon branch, bridges and other structures are numbered into the LU standard system. Signalling, power control and Rule & Regulations currently remain with NR. TPWS is already provided on the Wimbledon branch for NR trains. All this relates to the time before "a train protection system" was mandated by law. When class 165s were purchased for what became Chiltern, they came with tripcocks as a matter of course because that was the system on the Met line over which they operated. At some point once of the BR trial ATP systems was fitted to class 165s this line, but it wasn't applied to the Met. When TPWS was proposed as the means of complying with the "train protection" regulations, there were four sections of mixed running that needed to be considered. Chiltern, Silverlink to Watford, and Silverlink to Richmond already had trainstops and all the trains that normally used them had tripcocks. Thus nothing was needed although I understand that Railtrack/NR fitted basic TPWS to their sections of track to cover for the occasional visitors. LU dealt with occasional visitors to the Met. by other means (although even the regular rail head treatment train has now been fitted with tripcocks). LU was left to consider what to do on the Wimbledon Branch. It seemed unreasonable to require SWT to fit tripcocks to its entire fleet (which all had running rights over the section) or to restrict access to the small number of fleets that might routinely access Wimbledon depot (which would then have to have tripcocks). Thus, whilst TPWS was considered to be "less safe" than tripcocks/trainstops, TPWS was the agreed ALARP solution provided it was fitted at every signal, and is what was installed. |
|
|
|
Post by metrailway on Oct 25, 2015 11:59:41 GMT
As a mere layman, I can see risks if the system on the Met is basically a moving block system working in parallel with a fixed blocked system, as there is scope for confusion when there is a failure of some kind.
I can see a scenario where a NR train, after obtaining MA to pass a red signal, runs into the back of a Met train because the signaller has got their headcodes confused and therefore mistook the NR for a Met service. The NR train would not have any protection (bar the initial tripcock application).
I know in theory it shouldn't happen, but under pressure errors occur. I believe headcodes do go missing occasionally on modern signalling systems on NR or they are incorrectly applied.
|
|
|
|
Post by norbitonflyer on Oct 25, 2015 13:55:04 GMT
I can see a scenario where a NR train, after obtaining MA to pass a red signal, runs into the back of a Met train because . In such a situation my layman's understanding is that a driver given such a Movement Authority to pass a red signal is required to "drive on sight" - i.e at a speed slow enough that he can stop in the distance ahead he can see . The "Stop and proceed" rule on the Underground has the same requirement. |
|
|
|
Post by crusty54 on Oct 25, 2015 14:06:05 GMT
As a mere layman, I can see risks if the system on the Met is basically a moving block system working in parallel with a fixed blocked system, as there is scope for confusion when there is a failure of some kind. I can see a scenario where a NR train, after obtaining MA to pass a red signal, runs into the back of a Met train because the signaller has got their headcodes confused and therefore mistook the NR for a Met service. The NR train would not have any protection (bar the initial tripcock application). I know in theory it shouldn't happen, but under pressure errors occur. I believe headcodes do go missing occasionally on modern signalling systems on NR or they are incorrectly applied. The difference is it won't be a signaller. It's a fully integrated signalling system with computers with a human watching over it. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 26, 2015 8:52:46 GMT
As a mere layman, I can see risks if the system on the Met is basically a moving block system working in parallel with a fixed blocked system, as there is scope for confusion when there is a failure of some kind. I can see a scenario where a NR train, after obtaining MA to pass a red signal, runs into the back of a Met train because the signaller has got their headcodes confused and therefore mistook the NR for a Met service. The NR train would not have any protection (bar the initial tripcock application). I know in theory it shouldn't happen, but under pressure errors occur. I believe headcodes do go missing occasionally on modern signalling systems on NR or they are incorrectly applied. The difference is it won't be a signaller. It's a fully integrated signalling system with computers with a human watching over it. Correct. And in addition the system isn't relying on headcodes to differentiate trains - Seltrac will identify a CBTC fitted communicating train as a Met (or battery loco etc.) and anything else as an alien train and deal with it accordingly. Chiltern headcodes will be used only to put an ID on the train. If the signalling fails and the identity of the train isn't completely clear that is where the signallers need to ensure absolute clarity though, as Norbitonflyer says, any train in this situation should be at low speed. The detail of this part of the Seltrac system is still being discussed and confirmed internally and with NR and Chiltern. In answer to the earlier question, the proposed solution provides enough signalling capacity for the required service so there is no business case for moving to AWS/TPWS as far as LU is concerned and Chiltern are not contributing to the cost. |
|
