An interesting point in the Mott MacDonald options report https://orr.gov.uk/__data/assets/pd...te-train-protection-options-review-report.pdf is the qouted date of 2028 for ETCS L2 fitment on Chilterns. That is tantalisingly close to the 2027 date suggested for completion of enhanced TPWS, so assuming the ETCS date hasn't also slipped, The TPWS contractor would be just tidying up on site as the ETCS contractor is arriving behind them to rip all the work out again. I might tactfully suggest that doesn't sound like the best value strategy available! I suspect that this COULD all pan out like GWML where various strategies were mooted, but in the end they just went straight for the signals retained ETCS overlay which doesn't require comprehensive resignalling as it can be coupled up to the pre-existing SSIs in various ways. I note from the GWML project description that Alstom are using switched balises, which strongly suggests they are actually implementing a hybrid L1/L2 scheme that may not use continuous movement authority refresh via radio everywhere, possibly reserving it for busy junction approaches for better aspect update where it can make a performance impact (and replicate the effect of the fill-in beacons of the GW system). These techniques could probably also find practical application on Chilterns and would represent a long term solution, not a short term 'bodge'. The problem remaining is the rolling stock, however. GWML has more modern fleet profie, all already ETCS enabled or 'ready'. The Chiltern fleet will need equipping and varies in its 'readiness'. Parallel operation of Selcab and ETCS on the same surface tracks during a changeover could be an option but would need some study to see if a phased implementation across the fleet might be possible, as the MM report also highlights the difficulty accomodating the Selcab and ETCS equipment on the rolling stock simultaneously due to space constraints. Dual operation of the ACEC equipment and ETCS in the Heathrow tunnels was a major problem, but that was a specific issue about duplicated transponders provided in the ACEC system for reliability, an unusually high signal level from the obsolete ACEC equipment at exactly the same carrier frequency as ETCS, and a specific 'waveguide' effect found in the tunnel environment that meant the ACEC signal propagated over a very wide area and interfered with or overwhelmed the ETCS balise signal, causing dropouts resulting in failsafe (i.e. stopping) responses. ACEC transponders and ETCS balises worked fine together on GWML surface sections however.
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Network Rail and Chiltern Railways apply for train protection (ATP) exemption
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Anthony061
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I feel as if there's misunderstanding surrounding the completion date for Enhanced TPWS. It would appear that the scheme should be completed by mid-2024 and is expected to be in operation until 2027. With ETCS expected from 2028 and with the existing ATP obsolete, what would people propose to do in the intervening 8 years?
That's a good point. It may be the only option if rolling stock can't be made compatible with ETCS in some way by 2024, but another option could be a GW-style retrofit overlay ETCS scheme ASAP. OK that wouldn't so symbolically 'get rid of the lights on stick' in 2028 but it would get the job done in a modern future proof way, and Chiltern is a simple railway with few major signal structures and those that are there are not that old and presumably all have low maintenance high reliability LED head units anyway, so there's no particular urgency in getting rid of the whole existing signalling ecosystem by the supposed renewal date (subject to local expert condition assessment of course). So that's my proposal. Get them started on the design now, and when Alstom have finished on GWML in 2022, move them over one line clockwise radiating from London and let them do the same job on Chiltern by mid 2024. Meanwhile come up with some clever solution for rolling stock including renewing the older parts of the fleet if they can't be ETCS fitted.
Belperpete
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Removing the existing ATP from the trains first, could be much the easiest way to fit ETCS. There may not be room on-board the trains for both the existing ATP and new ETCS electronics boxes and their displays. While ETCS can in theory accommodate "country specific" modules for existing train protection systems (as it will for BR AWS/TPWS), I should imagine implementing such a module for an obsolete ATP system that the manufacturer no longer supports could require some "interesting" development work. And that assumes things like the train-board sensors are still working, and there is room for both them and the new ETCS balise readers.
TPWS/ATP isn't installed on the Met, it's all trainstop/tripcock protection, which will be remaining after the resignalling for the use of Chiltern trains.
The Mott MacDonald report suggests that room for both the new ETCS and old ATP equipment could not be found onboard, especially on the cl. 165 units. I agree developing an STM solution for an obsolete ATP system that would then be immediately ripped out would be a total waste of money. I would research going for a dual fitting solution with ETCS and ATP working in parallel and migrate the fleet across, then when the last ATP unit has been converted, remove the trackside ATP. That would require the new ETCS to effectively replicate the functionality of existing ATP, which should be fairly easy but wouldn't 'do away with the signals' which seems to be such a bone of contention for so many people.
ETCS trains can also have the 1909 vintage technology, just as the LUL S-Stock has alongside its whizzy new Seltrac equipment.
HSTEd
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Shouldn't they just move Chiltern to the front of the queue for resignalling and put ETCS L2 in?
They've known about this problem since at least 2012.... why is Chiltern not in front of the ECML project for example?
They've known about this problem since at least 2012.... why is Chiltern not in front of the ECML project for example?
Because that's a complete resignalling if done in the conventional L2 way which the infrastructure isn't old enough to justify currently. An overlay on the other hand using Alstom's flexible ATLAS tech as on GWML (other suppliers offering similar solutions are available) could be quicker and more cost-effective, but there's still the rolling stock issue to resolve.
Moorgate and NCL is front of the queue as replacing the 1970s approach control is allow and increase in service levels.
The ECML first approach is crucial to a national programme happening or not
HSTEd
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Well the obvious way to solve the rolling stock issue is to order a new fleet of units for Chiltern (195s or similar) modified to have space for all the equipment.
Then cascade the existing units elsewhere and remove the ATP gear.
The problem with new stock is that you would either have to lock yourself into DMUs for the forseeable which is not a great idea for a London terminus or go for (at least) bi-modes coupled with electrification - suddenly ETCS fitment has turned into wholesale upgrade on a similar scope to GWEP, and fudging ATP for a few more years looks very attrractive
HSTEd
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You can just cascade the new units elsewhere at some point in the future if electrification ever actually occurs.
We still have a requirement for a large diesel fleet for the forseable future.
The Planner
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There are more pressing signal boxes to sort than Marylebone. You'll find that NR won't take on more than one "big" resignalling per route per control period.
Nym
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Except that the ETCS EVCs don't support more than one other protection system, and I would put money on said system being selected as AWS/TPWS Four / Mk.4 as this is needed for talking to ETCS properly. Hence, tripcocks won't be able to be supported in combination with ETCS unless the TPWS system is modified to also support tripcocks within the TPWS controllers, which is a significant redesign for Thales or Unipart which I just don't think they'll be willing to do.
charlesn132
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Out of interest, is that the approach used for the class 717 tripcocks?
Nym
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Unknown, I haven't worked on ETCS on new units, only retrofit (and even then not for a couple of years now).
My suspicion is that there may be some form of manual changeover provided on them as is the case for GW-ATP and ETCS on the GWR IETs.
That requires quite the reboot to move from one to the other on them, and requires the desk to be shut down to do it.
My suspicion is that there may be some form of manual changeover provided on them as is the case for GW-ATP and ETCS on the GWR IETs.
That requires quite the reboot to move from one to the other on them, and requires the desk to be shut down to do it.
philthetube
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I don't think you are correct on that, as I understand it they are switching to the protection used on the rest of Chiltern's operations
One of the reasons for the switch is to get rid of trainstops which are expensive to maintain,
I Was wondering if the LUL system would need a seperate derogation as it is very primitive compared with modern systems, although very effective.
A clear example where there are multiple systems supported simultaneously are the Class 345s, which support ETCS (for the GWML, later only Heathrow branch), Trainguard MT (for Crossrail Core), and AWS/TPWS on what one might call "legacy" routes.
It's been a long time since I've looked into ETCS, but from memory there was never anything technically stopping an arbitrary number of STMs (and I believe some stock that runs internationally on the continent has such systems, given the need to deal with legacy systems on cross border routes).
bluegoblin7
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Just to pull together all the LUL-related bits and bobs:
There is no AWS/TPWS/ATP on the shared section between Harrow-on-the-Hill and Amersham. All train protection is in the form of LUL standard trainstops/tripcocks and full-speed overlaps. There are no plans to fit any of these systems on this part of LUL infrastructure.
Under the Four Lines Modernsation (4LM) resignalling plans, using Thales Seltrac/CBTC, the Main Lines on the shared section are to remain equipped with colour-light signalling and trainstops for Chiltern Railways services. This is in the form of the 'underlay' system, meaning that (new, most are now installed) line side signals will be driven by the CBTC system. Met line Operators will drive to their in-cab signalling, Chiltern drivers will drive to two-aspect* lineside signals. (*The new signals are technically three-aspect, with yellow replaced with blue; this means that trains that are fitted and communicating with the CBTC system can proceed into an 'occupied' section, but must be treated as a red signal by unfitted trains.)
All of this is already in development and installation, although most of the 4LM programme beyond SMA8 is now under review. However, the age of the signalling north of Harrow does mean that some kind of resignalling will be required in the near future.
Given TfL's wider funding constraints it's extremely unlikely that there will be any change to the protection systems provided for Chiltern services without some kind of external funding...
Perhaps at least on the outer reaches of the subsurface network, where capacity has never really been a major issue, LUL should go for a simple digital balise-based replacement of their mechanical trainstops such as that being installed on the the Berlin S bahn: https://en.wikipedia.org/wiki/Zugbeeinflussungssystem_S-Bahn_Berlin
Such a system should be able to be emulated readily by standard ETCS fitted mainline units that share parts of the same infrastructure.
bluegoblin7
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Any benefits to LUL trains would be quickly wiped out by the additional costs of a completely different system. As I've already pointed out, much of the infrastructure and installation is already underway.
LUL and NR are completely different beasts. What is right for NR is not necessarily the right answer for LUL - capacity is far from the only consideration here. Let us not forget that SSR resignalling is already on its third iteration.
LUL and NR are completely different beasts. What is right for NR is not necessarily the right answer for LUL - capacity is far from the only consideration here. Let us not forget that SSR resignalling is already on its third iteration.
It's OK, I'm musing on an alternative history rather than seriously suggesting that what is contracted for and partially constructed is undone ... again! However, if the new Thales system can drive simple old-school colour light signals and trainstops on the shared sections, as planned today, then plausibly it could drive active Eurobalises via LEUs from the same outputs in the future if there were suitable trains to use them.
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