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Post by dm1 on Aug 13, 2023 11:56:24 GMT
I'm guessing the idea is that the larger and more evenly spaced doors on the new trains will reduce dwell times enough to enable the higher frequency throughout the line.
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Post by dm1 on Jun 2, 2023 20:48:46 GMT
Does anyone know exactly when the 1100mm platform height for Crossrail was decided? Crossrail has been criticised for adopting this non-standard height, but as far as I'm aware there were no trains with 915mm level boarding on the UK market around the late 2000s - early 2010s when this decision must have been made. The Stadler Anglia units have 915mm doors but sloping floors within, which aren't suitable for metro operation. I think the first 915mm flat-floored UK trains are the Merseyrail 777s which entered service in January 2023, which is over six years after the original December 2016 target date for class 345 entry to service. That left Crossrail with the choice of putting the onus for level access on the platforms (easy and low risk compromise) or on the trains (theoretically ideal, but dependent on developing a new train architecture with all the risks involved - and ideally dependent on multiple bidders being willing to commit to develop a new train architecture if they were awarded the contract). There was the S-Stock running within TfL, which while not entirely mainline stock, was close enough that a version for Crossrail would have been absolutely feasible. Not to mention numerous types of stock on the continent with floor heights even lower than 915mm, while still having entirely level floors. That all recently built rolling stock does not have level boarding is purely a procurement failure as it was not specified in the tenders, not because it was particularly onerous given all the major manufacturers' offerings elsewhere.
At design stage, even passive provision for adjusting the core to 915mm platform heights would have been a good idea (probably ensuring the approach and platform tunnels were large enough to raise the track up slightly), but to my knowledge this was not done.
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Post by dm1 on Jun 1, 2023 23:03:54 GMT
I find it hard to believe that construction of a new public building project, such as Old Oak Common Elizabeth Line, does not automatically include step-free access as part of the design. That is caused primarily by the specifications for the central operating section (COS), Heathrow tunnels, and trains all being incorrect/not following the national standard. The COS and Heathrow stations have platform heights of 1100mm. The entry height of the Class 345 trains is 1100mm. The national standard platform height, to which all the other Elizabeth line stations and all NR stations should be built to is 915mm. Presumably 915mm has been specified for Old Oak Common, to enable level boarding from mainline rolling stock when new rolling stock is procured that meets the national standard (like the Class 745, 755 and 777, and the S-Stock). Specifying 1100mm would allow level boarding from the Class 345, but not for any other rolling stock that has level boarding elsewhere. It also causes problems for freight as the 1100mm platform infringes on the loading guage. The better call would have been to specify everything at 915mm, but that boat has sailed and now the designers are stuck between a rock and a hard place, with the choice between level boarding now, but with operational restrictions on freight and permitted rolling stock, or level boarding for future non-EL rolling stock, but a step for the EL.
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Post by dm1 on Jul 12, 2022 12:47:14 GMT
Slightly off-topic, but does LU use 'shunting' shifts?
As in, instead of drivers stepping back, Driver A enters terminus in service, drivers B and C enter the train at the back and front respectively, C drives it into the siding, driver B out of it, and in that time driver A has walked to the opposite end of the opposite platform and drives their train back along the line. Drivers B and C walk across the platform and do the same for the next train.
This has the advantage of drivers staying with their train throughout their shift (apart from breaks), while still allowing extremely short headways, particularly if there is more than one reversing siding and an island platform. Drivers B and C have a slightly more monotonous shift, but wouldn't that be much simpler to roster operationally, compared to stepping back 4 trains?
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Post by dm1 on Mar 23, 2022 0:28:54 GMT
Sorry to shock the uninitiated but is up to you to seek out the information you require. LU doesn't have the manpower or resources to ensure you are kept fully informed via your own personalised one to one specific information portal. I don't think anyone is asking for that, but saying there is a "Good Service" on a line when a part of it has so many trains cancelled that the headway is doubled (e.g. hourly instead of half-hourly) is the opposite of truthful and useful information. The fact is TfL actively hide information about which specific trains are cancelled. As soon as there is any disruption on the northern end of the met the published timetable becomes a work of fiction and it becomes quite difficult to find out when trains are actually running, even if one wanted to. It is not publically available to seek out.
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Post by dm1 on Mar 19, 2022 14:33:24 GMT
The issue is that "Good Service" implies that the line is operating normally and that there is no disruption.
On a line with a high frequency and few branches you can probably get away with a train or two being missing before this becomes noticable, but on the Met that just doesn't work.
Particularly on the outer reaches of the Met, if even a single train is cancelled, this needs to be communicated clearly. "Minor Delays between Harrow on the Hill and Amersham/Chesham" would be the minimum in this case, but even better would be treating that section of the line as the timetabled service that it is and announcing "The XX:YY service from Harrow to Amersham is cancelled" for each train.
Treating a 30-minute service the same as the Victoria line helps nobody and only leads to frustration for passengers.
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Post by dm1 on Mar 3, 2022 23:59:46 GMT
If the intention is to fit PEDs in any case, then the 'suicide pit' becomes much less relevant. Isn't their main purpose drainage anyway?
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Post by dm1 on Jan 29, 2022 15:42:24 GMT
I'm not sure this video has been shared here yet, but it may go some way to explaining how this situation happened.
When the engineers designing the trains don't physically have access or contact with the mock-ups or the people testing them due to covid restrictions, then it was probably inevitable. Video calls only get you so far.
The good news is that this problen has been caught now, before too many of the trains have been built. Otherwise the costs would probably have been much higher.
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Post by dm1 on Jan 29, 2022 14:19:25 GMT
The SBB have an app that does pretty much exactly what you are describing and works very well. I think it uses a combination of GPS, mobile data and bluetooth beacons on the trains to make it work. www.sbb.ch/en/timetable/mobile-apps/sbb-inclusive.htmlReally the only hurdle to making a similar app for TfL is feeding it reliable data. Unfortunately that has been a problem for decades and the fact that there are numerous, old, incompatible systems involved means it would probably cost a fair amount to implement reliably.
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Post by dm1 on Jan 29, 2022 0:40:24 GMT
DMI placement and specification are also a real problem on LU in my experience of using it, probably a much bigger problem than audio annoucements.
Why dot matrix displays with line sizes that are clearly too small even by TfL's own standards are still being installed is beyond me. Particularly where they have been used to replace older DMIs that were much larger and much more legible. High quality, well-designed, large LCD/TFT/OLED displays should be the standard these days, but I suspect the Elizabeth Line will be one of the few places to have something resembling this when it opens.
I would say the the issues on LU with announcements and passenger information are somewhat different to those on NR, just because TfL's information is generally better already, and the nature of the lines mostly having consistent stopping patterns.
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Post by dm1 on Jan 28, 2022 23:39:33 GMT
I suspect in that case the problem wasn't just the contents of the announcement but also its intelligibility.
A muffled, mumbled announcement from poor quality speakers transmitted with a poor quality microphone, where one of the few intelligible words is "emergency" is going to cause unfamiliar passengers problems. That suggests that focussing on making sure announcements are always intelligible and clear is very important.
One of the posts in that thread suggested that the phraseology used in the announcement may not have been standard either, particularly the use of the phrase "emergency braking".
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Post by dm1 on Jan 28, 2022 11:47:36 GMT
You don't actually need text to speech. You just need the driver to be able to trigger the relevant announcement visually without the recorded audio announcement being played, allowing the driver to announce it manually.
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Post by dm1 on Jan 27, 2022 15:20:44 GMT
I don't think that the "Change here for..." announcements are necessarily superfluous. They allow unfamiliar passengers to build an intuitive mental map of the network while they are travelling on it, that they can then use on future journeys. With a network as complex as the Underground, at least in my experience, it's quite helpful.
On LU I think a bigger problem is the dot matrix displays on the trains. The displays are quite small, but the announcements quite verbose, so it might be worth trying things like "Next Station: X", "Destination: Y", "Change for: A, B, C", where the bit before the colon is static and the bit after scrolling if necessary, and static if the station name is short enough to fit. That way the useful bit of the information would be on the display for much longer, rather than having to wait for "The next station is" to scroll past every time. In the audio announcements that phrase serves mainly to attract attention instead of using a chime, but on the visual displays it takes up space. As mentioned on another thread, the displays on the S-Stock going blank on approach to each station is also rather unhelpful.
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Post by dm1 on Jan 24, 2022 18:05:42 GMT
Quite apart from time seen as wasted between stations, I'd like to see the ATO final 'flare' to a stand improved and CSDE asserted as soon as the train stops. There's at least 2 seconds wasted every stop on these. 2 seconds per stop is 84 seconds lost from Ealing Broadway to Upminster. Not far short of a minute and a half... Compare this with the flare, stop and door release on Central and Victoria lines to see what I mean. No messing, the train arrives, stops and the doors open, no real delays. I can remember being really worried about up to 300ms to get the S stock's pre-ATC CSDE to act. Turns out to be as nothing by comparison! I hope they sort out Moorgate - Liverpool St. That is annoyingly slow for the past 2 years. I cannot understand what the point is of the train practically coasting between these two stations, when in the opposite direction it leaves at normal speed and does not do anything like this. I'm not very well versed on the gradients around that area, but could it be that the train is just coasting on the downward gradient to save energy, given that it does not need to go any faster to arrive on time? Then it would make sense that it does not happen in the other direction as it would then be going up hill.
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Post by dm1 on Jan 12, 2022 23:42:28 GMT
Wikipedia lists the S stock acceleration as 1.3m/s^2, same as the 2009 stock, but the latter feels much faster, even on CBTC sections.
Is the full acceleration actually being used anywhere yet, or have the trains I've been on just been too punctual and therefore going slower?
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Post by dm1 on Dec 18, 2021 14:17:51 GMT
Surely this has to be a backward step. I cannot understand why would they develop a system that cannot even take out of service trains, no matter what length of the train it is. You would think in this world of software you can do so much, but it seems even worse. I am sure if this was 40 years ago, any train would have went through there as long as there was no clearance issues. By definition any in-cab signalling system moves part of the signalling from the infrastructure onto the train. Therefore in order to operate a train on the infrastructure safely, it has to be equipped with the right equipment and software on board. That does mean some loss of flexibility, but in theory it also means much less maintenance on the tracks, as there is much less to go wrong (no trainstops or signal aspects to fail for example). Since Crossrail was never designed to be an interoperable railway, that flexibility is also not really needed. Once it is open 99% of the trains will be Class 345s, and any engineering trains can also be fitted with the system or operate in blockades as necessary. The reason 7-cars can't go through the tunnel is that at some point the software on them was frozen and only the 9-car software was worked on, in order to avoid needing to maintain two software versions at the same time. Therefore the 7-car software is now several years out of date compared to the 9-car software, so is no longer compatible with the signalling. Given how late and problematic the software development continues to be, that was probably a wise decision, even if it does mean occasionally towing a train the long way round.
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Post by dm1 on Dec 18, 2021 14:05:56 GMT
A key point in all this is that ever since man devised rotating electrical machines, as far as traction is concerned, the asynchrnous AC motor has always been the holy grail, right back to Victorian times. The difficulty of controlling the adaption neccessary from the transmitted supply to the motor always held it back. A slight correction, in that increasingly synchronous AC motors are making a comeback in a big way, especially for trains. In particular Permanent Magnet Synchronous Machines (PMSMs) are proving popular, due to their higher torque density compared to asynchronous or DC motors. To very briefly try to explain how they work - a syncrhonous motor is effectively a DC motor, where the rotor and stator swap places. So instead of supplying a DC voltage to the stator and and an AC voltage to the rotor (created by the brushes), in a synchronous motor you supply an AC voltage to the stator and a DC voltage to the rotor. But supplying a DC voltage to the rotor is cumbersome mechanically, so it is possible to replace it with permanent magnets instead (to continue the analogy with the DC motor, it's the same idea as when you build a simple DC motor from a a horseshoe magnet and a coil of wire, but in reverse). There are certain differences between the speed-torque curves of synchronous and asyncrhonous motors that can be advantageous in certain situations, but I won't go into that here. I can't find a source at the moment, but I seem to recall reading somewhere that the new Siemens Tube stock will be using PMSMs. There are various trains around the world that use them - the main argument against them is that the extremely powerful but small magnets needed are very expensive, compared to the coils of wire you need for an asyncrhonous motor. The power electronics and control circuitry is also fairly challenging.
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Post by dm1 on Sept 21, 2021 21:50:21 GMT
I guess by the time two platforms becomes a serious limitation, it will be worth extending the line further (towards Clapham Junction?), where sufficient platforms can be built for the demand by then.
Alternatively, maybe we will have moved away from more or less requiring all reversing to occur at platforms. With future walk-through trains, there is no real reason to require a train that is reversing straight back into the station to be cleared so diligently of passengers. Then you could build a few extra reversing sidings behind the station, which are significantly cheaper than extra platforms and would provide far more capacity. I realise that may be a slightly controversial opinion here, but termini configured in this way on metro systems are standard practice around the world - and given the NLE is new, the arguments about it not being possible due to the age of the system don't really hold.
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Post by dm1 on Aug 25, 2021 13:53:44 GMT
". Don't write off the trolley bus. They are still alive and well liked in many countries - but OK I am not aware of any remaining TFL systems. Battery technology has come on in leaps and bounds recently. It is unlikely that new trolleybus systems will be developed in the near future, given the e capital cost and inflexibility. There are, however, proposals for heavy trucks to use external as batteries are not (yet) an option there. If the infrastructure exists, perhaps buses or coaches could make use of it too? Battery trolleybuses are a thing, and as it stands by far the most cost efficient and environmentally friendly bus option in many cases, especially in places like London. The batteries are smaller (less environmental impact during assembly and also far lighter), can be charged on the move (fewer vehicles and drivers required, lower strain on the power grid) and the buses have far more passenger capacity than battery equivalents (due to axle limits). Trolley poles can drop and rise at the push of a button and within the dwell time of a single stop, giving them far more flexibility than a lot of other e-bus types Battery trolleybuses can have up to 50% of the route off-wire, meaning only straight, cheap-to-wire sections need to be wired up, without any complex junctions. You can even power them using the same transformers and substations as the underground. Personally I think the main reason they haven't long since made a return to London is ideological opposition within TfL and the DfT, and them not realising just how far trolleybus technology has come (as there are no working systems in the UK). A small amount of infrastructure on a few central streets in London (at probably a similar or lower cost than the opportunity charging stations being built everywhere) would enable massive, rapid electrification of nearly all bus routes in Central London, without lots of the negatives of opportunity charging or depot charging buses.
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Post by dm1 on Aug 18, 2021 19:14:29 GMT
The working timetable doesn't appear to have been published online yet (unless I haven't found it).
Is "to better reflect actual performance" a euphamism for "slowed down", or has it been sped up?
Could someone describe the southbound changes in more detail? Is there a significant change in journey times between Amersham/Chesham and Baker Street/Marylebone?
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Post by dm1 on Aug 9, 2021 18:49:23 GMT
Many of the issues around information on the met line seem to stem from the age-old problem that the outer reaches of the line are on paper london underground lines (turn-up-and-go, no timetable necessary, headways more important than exact timetable), but are used more like a standard suburban rail service (low frequency, passengers turn up based on the timetable, if a nominially 30-minute service turns up 20 minutes late, it is extremely annoying for them).
The information communicated to passengers by TfL assumes the former, but due to the low frequencies at the outer edges of the line, that information is basically useless - leading to the black holes reported above. In that situation, much more detailed information is desirable - either specifying which timetabled trains are and are not running, and trying to stick to the timetable, or at least giving public information about the actual service being run and its timetable/frequency. The met line, unlike most tube lines does have an official, customer-facing, published timetable for the Amersham/Chesham branches at least.
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Post by dm1 on Aug 9, 2021 18:38:35 GMT
The better solution would probably have been designing much more flexibility into the customer infromation systems on the trains from the start. Such unusual service patterns during engineering works are nothing new and the system could have been designed to correctly display any service pattern that can physically be run on the SSR network. Displaying "Hammersmith & City line to Upminster via Barking", or even having the displayed line/destination change automatically at the relevant location once the destination and route has been entered into the system would have prevented these issues entirely. I am aware that the computer systems on the S-stock are somewhat archaic, but systems that can deal with situations like this have been around for decades now - not least on numerous bus information systems on the continent. Perhaps d7666 can elaborate whether such flexibility will arrive with 4LM. It would certainly help.
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Post by dm1 on Jun 6, 2021 21:49:00 GMT
Whilst I can appreciate that these are unusual times and that there is no doubt a good explanation for the ongoing problems, not being able to run the timetabled and advertised service so extensively is something that just shouldn't be happening. The seemingly very poor communication makes it even worse. To put it another way - the more often an unreliable service causes passengers to seek alternative modes of travel (on the met line generally the car), the more likely it is that those alternatives will become permanent. That is not good for TfL, nor for the environment in the long run. You simply can't just not run a service at evenings and weekends without warning and expect the line to remain attractive to passengers. The existence or absence of a good reason for this situation within TfL internally doesn't change that. Therefore whilst I disagree with the tone of eastlondoner123, I can understand the underlying frustration. MoreToJack I would be very interested in that response. It would also be interesting to get an idea of when the control room issues might start to be resolved.
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Post by dm1 on Jan 20, 2021 15:10:59 GMT
Oh, thank you. Is an inverter kind of a rectifier back-to-front? BTW, I gather the output from West Ham "A" power station, built by the County Borough to feed its tramways, was 2-phase .How did it get changed to 3-phase to power the trolleybuses? Mods - sorry to digress. I should obviously have paid more attention in O Level physics! Functionally, yes, one does the opposite of the other, and they use many of the same components. However their circuits are laid out differently - you couldn't turn a rectifier back-to-front to make an inverter. Although there are many different circuits designed to act as both inverters and rectifiers - that is for example how regenerative braking works in modern rolling stock. 25kV AC (if present) gets transformed to a lower voltage and is rectified to about 750-1000V DC (if using third/fourth rail, then the DC is fed directly). That DC voltage is then fed through power electronics (effectively a fancy inverter) that nowadays generally generates a variable-frequency three-phase AC voltage that powers the motors (that would be the case on the new AC motors on the refurbished 92TS). During braking, the motor functions as generator, generating that same 3-phase voltage. The power electronics (that was acting as in inverter before) now acts as a rectifier to supply 750-100V DC again (which in third/fourth rail is fed back directly). If using 25kV AC, then this DC voltage is inverted to 25kV 50Hz and fed into the catenary. The reason for this back and forth inversion/rectification is that AC electrification uses a single phase at fixed frequency (in the UK 50Hz), whereas the AC motors need a variable frequency three-phase supply to be able to operate at different speeds efficiently. In LU world the supply is DC, but nowadays AC motors are used because they are smaller, more efficient and require less maintenance than DC motors. However they only really became practical once semiconductors and power electronics developed (earlier GTO thyristors, nowadays mostly IGBTs). So on LU you would only need DC <-> variable frequency 3-phase AC conversion. Hopefully that's a helpful (simplified) summary - it gets quite complicated quite quickly, but in short some rectifiers are also inverters, some inverters are also rectifiers, and some can only do one or the other.
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Post by dm1 on Jan 16, 2021 12:45:58 GMT
Perhaps they mean a rectifier with an integrated transformer to go from medium voltage grid AC to low voltage DC. You can't rectify e.g. 11kV AC to 750 DC without a transformer and/or power electronics.
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Post by dm1 on Dec 8, 2020 13:49:32 GMT
That's common practice elsewhere. You could in theory "replicate" the chime using a special symbol (e.g. a warning symbol) a the the beginning and end of the special announcements on the DMI, although that is obviously slightly less useful than a chime as it requires somebody to be looking at the screen, but should be enough for RVAR.
What's also helpful is using a different voice for unusual announcements - either a male voice, since the S-Stock generally uses a female voice, or just a different female voice.
In many other systems it's common practice for staff in the control centre (I don't know what their exact title is) to record announcements about any disruption on the fly, then broadcast them to trains and stations. That also works quite well, but ideally requires those staff to have some level of diction training to ensure they are properly understandable.
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Post by dm1 on Sept 2, 2020 18:48:07 GMT
I wonder if there isn’t a little but of self declared specialness which may not fully be justified. I'm wondering the same thing a little. Especially given that the delay from the step extending is no longer than the delay on the Jubilee line when the ATO system is 'thinking' before the doors open. The Jubilee seems to manage its frequency just fine even with this delay.
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Post by dm1 on Sept 2, 2020 10:34:32 GMT
I don't know the details, but I assume there is an interlock of some description - perhaps even mechanical. If the step fails for any reason, on mainline stock the door is just locked out of use. That's probably not very desirable on tube stock, but it happens rarely enough that I doubt that's a huge concern (handle it in the same way as a door fault - take the train out of service as soon as practical)
There are safety considerations - but it's been done before. These are solved problems, there's no need to reinvent the wheel.
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Post by dm1 on Sept 2, 2020 8:48:30 GMT
Generally they're designed to be routinely stepped on. They're also used for level access for wheelchairs or pushchairs.
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Post by dm1 on Sept 1, 2020 20:56:25 GMT
This example claims they need 50mm of space under the door. That isn't all that much.
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