david.hill64

Phil some speculation in your comment I think. You imply that the central core has been built to a very restricted loading gauge!!! We seem to have been able to run construction trains and 345's in the tunnels without problems. 345's apparently cope well with standard UK platforms and those in the Crossrail central section. My assumption is that the civil infrastructure in the tunnels conforms to the passenger train and civil works TSI's which themselves contain an opt out to let UK continue to use the existing gauge throughout the system. The electrification works might even conform to the Energy TSI as the use of PSD's will have mitigated part of the risk. Trainguard: depends on when the choice was made. The argument for the derogation appears to be that the core needed moving block which as you rightly say is not a proven product as ETCS level 3. Hence the moves to allow an ETCS 2/3 hybrid. (Just to say again that Bombardier has supplied a fully functional mixed traffic ETCS level 3 look alike system to Turkmenistan (I think: it's one of the -stans). But it uses TETRA not GSM as the carrier so doesn't count). But Thameslink, which is ETCS level 2 has a 30 TPH design through the central core. Given that if we had remained in the EU, Trainguard would have to be ripped out soon and replaced by ETCS, it would have been more sensible to adopt ETCS level 2 throughout. Although Trainguard is a proven product, every metro signalling system is tailored to its application. The wording of the derogation implies that a 'communications bearer capable of supporting ETCS' ie GSM radio , shall be installed as part of the initial installation. What isn't clear to me is whether the intention is that GSM should be used as the data carrier for the Trainguard system. If it is, then it is a completely new development of Trainguard which typically uses 2.4GHz and 5.2GHz Wi-Fi signals as the data carrier. Moreover in the application of Trainguard that I am currently assessing, the use of twin frequencies is a cornerstone of the safety case. If Siemens has had to move away from this - and being 6000 miles away from Crossrail I have no idea what they are actually using - it would have been a significant development. Hindsight is a wonderful thing, but it seems that Crossrail and Thameslink were unaware of what each other was doing. Otherwise we might have had only ETCS and TPWS/AWS as the onboard systems, and saved a fortune. Finally more comments about the derogation. It permits CBTC to be used until ETCS is capable of supporting ATO (already in use in Thameslink), communications with PSD and auto reverse. The Bangkok skytrain CBTC system is a metro version of ETCS level 2 and already supports both communications with PSD and auto reverse. The conditions for the derogation to end may well exist before Crossrail is commissioned.

The reasons are contained in the European Commission's derogation that permits temporary use of the Siemens Trainguard CBTC system in the central core. The EC determined that Crossrail is part of the UK national rail network and therefore falls under the scope of the interoperability directive which demands compliance with the TSI's. In respect of signalling this means using one of the ETCS levels. I would be interested to understand why TfL thought it necessary to continue with Trainguard rather than using ETCS level 2 as per Thameslink especially since if we had remained in the EU migration to ETCS would have been required.

OK that makes a lot of sense, thanks. Last time I used HEX it was still in the hands of the original HEX units. I recall that ETCS was trying to incorporate modules that allowed the onboard ETCS equipment to read wayside telegrams from legacy ATP systems and drive the ETCS ATP that way. There was even a suitable acronym for the modules but it's slipped my mind. I've been away from ETCS development for a while. If it hasn't been able to work then I am not surprised. I was surprised that the IET's have the Alstom ATP system fitted: they must have dredged the bottom of the spares barrels (or took equipment from HST power cars (???)) to equip the trains. For me, the next interesting thing will be to see if the government decides to let the Crossrail central core CBTC system live out its natural life rather than being replaced by ETCS level 3 when that becomes available.

What happened to the GW ATP system? I thought that HEX used that.

Ken, are the gas tanks brass tube? Cheers Dave

Unlikely and it wouldn’t be sensible to abandon an integrated set of standards too quickly. The short term exception in my view would be the electrification clearances in the Energy TSI. Reverting to the proven safe BR standard would knock hundreds of millions off the cost of electrification.

The rolling stock TSI (technical standard for interoperability) requires a standard of headlights but not yellow ends. As the TSI is mandated by EU law it supersedes national standards. EU countries are not permitted to deviate without a derogation from the European Commission. RSSB in its guidance note states that there must be a risk assessment if yellow is not used as an additional safety measure, but cannot force the issue.

Good heavens Ken! How many minutes did that one take?

I think that New York has installed external voltage regulators before the UPS systems to protect against over-voltages, which were becoming more common. When we installed signalling systems in Thailand, India, Pakistan etc we would always ensure that the power supplies were capable of dealing with the relatively unstable incoming power. I guess UK is heading that way.

Don't get shirty! I did read the article, which I though was constructive and informative. Clearly all of the available power supplies had the same problem, which isn't surprising if they are all from the grid. My point is that if we can no longer rely on stable power supplies within the correct specification, then the industry will have to spend money to compensate for the deficiencies of our new generation system. Yes the system shut itself down to protect itself, but it would be more sensible for the protection to be upstream of the conditioning/UPS/secondary source so that the UPS kicks in when the power is out of spec. It may not have been necessary before but recent events are likely to be the precursors of the future so thinking will have to change. Working in countries where mains power supply isn't as good as that which we (used to) have means that the protection on essential circuits is arguably better than we have. If you had read my comment properly instead of getting in a huff I think you would have understood that I was getting at the grid not at NR.

All very sensible, so I wonder why an over-voltage can bring down a whole area? Presumably this protection wasn’t yet fitted.

Interesting. As we rely more and more on intermittent sources for power generation, I wonder of we will need to change the thinking behind powering signalling systems on the mainline. In every metro signalling installation I have been involved with all signalling supplies are conditioned by a UPS system, usually fed from two independent sources and a diesel generator in addition to the battery back-up. A voltage spike wouldn't crash the system.

Brilliant! Thanks for starting this thread.

What's next Ken?

Jim, the GW and Chiltern ATP schemes were pilots to try different ATP technologies as an overlay to the standard BR signalling. They were installed following a post-Clapham assurance by BR that ATP would be fitted (even though Clapham was not ATP-preventable). Railtrack redid the cost benefit analysis and showed that the costs of ATP as an overlay to the existing system were disproportionate to the benefits. Hence the development of TPWS which was intended as a short term interim measure pending roll-out of ETCS level 3, which was seen at the time to be about 5 years away (ie available by 2000). Well we all know what actually happened. With communications based systems such as ETCS level 2 and 3, ATP is essentially free (well, very little cost). ATP does prevent the low frequency high consequence events that TPWS cannot prevent, such as a high speed SPAD where TPWS may not stop the train before the conflict point. I have worried for the last 20 years about an ATP preventable accident on a TPWS section. Though as it happens the benefit of TPWS is now though to be rather higher than that used in the original analysis. If we were not to fit ATP when installing new signalling, in the event of an accident the consequences in court for those having made that decision would be dire, and rightly so. I accept that ETCS does have operational restrictions and I expect with wider implementation more work-a-rounds will be found.

Some observations: The Cambrian ETCS implementation was a pilot scheme. I would be very surprised if the installed system is to the latest hardware and software specifications. ETCS gives you ATP as an integral part of the system. While TPWS is good (disclaimer: I have an interest as I led the team that developed the concept and had it agreed by DfT and the Railway Inspectorate - other members of this forum were on the team), TPWS cannot provide the same protection against the low probability but high consequence events that ATP prevents. If you are re-signalling you really want ATP. ETCS is suitable for speeds above 125mph. It has been determined that lineside signals are not. ETCS would therefore allow some line speed increases on WCML/ECML. Until the end of next month at least, fitting of ETCS is a legal requirement when re-signalling (as opposed to maintenance replacement). Even after that there will be a strong commercial case for following the ETCS standards. (Though there would be an opportunity for minor deviations to allow something like the ETCS level 3 lookalike that Bombardier has implemented outside the EU). ETCS allows ATO which can give a more reliable timetable adherence in high density sections such as Thameslink core. With ETCS 2/3 you could, in theory, abandon all lineside signals, track circuits and axle counters. In level 3 particularly these serve no purpose except as a fall-back if the ETCS fails. But given that ETCS hardware is mostly duplicated with hot standbys on board and at wayside, system failures are rare. (Bangkok Skytrain uses a specifically designed metro version of ETCS and has no signals except in the depots, with no main line track circuits or axle counters). Removing the lineside systems reduces failures and costs.

No, which is one of the reasons why axle counters find favour. Neither track circuits nor axle counters are required with ETCS 2/3 but are provided for back up.

No, which is one of the reasons why axle counters find favour. Neither track circuits nor axle counters are required with ETCS 2/3 but are provided for back up.

But it’s not just a software change. The hardware would also have to change. New safety cases required so altogether a very expensive mod on a little used line.

Actually the reverse. Sand improves adhesion which allows the braking force to be transmitted through the contact patch without causing the wheels to slide. Wheelflats are caused by a locked wheel leaving an area of low adhesion and entering one of normal adhesion. The sliding friction at the interface then causes a metallurgical transformation of the steel in the wheel. The resultant compound, martensite, is hard brittle and cracked. It then spalls from the wheel leaving a depression that becomes a flat under the rolling action of the wheel. It is perfectly possible to have a flat on only one wheel of an axle if only one rail is heavily contaminated but flatting both is more likely.

Don't forget the 5 Brush class 48 locos. The only data panel I ever photographed was from one of these as I guessed it would not be around long.

At £10 per mile we could reopen everything! £10m per mile may be a ball park.

Somebody posted the answer to this recently. There was a Derby based set that retained the maroon livery well into the 70's...........now who posted that?

Actually most of the vehicles that I have been involved with in recent years - admittedly in Asia not UK - have inter-car anticlimbers as standard. All with monocoque construction. i understand the problems of Mk 1 construction where the sole purpose of the bodyshell was to keep the rain off the passengers........

Very interesting: thanks for posting. There doesn't seem to be any sign of anti-climbers. I wonder how that function is provided. Anybody know?