Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Aug 19, 2023 21:13:08 GMT
I really wish TFL were able to negotiate a deal now with the 4LM team(supplier) to rapidly extend their signalling system to the Piccadilly rather than messing about trying to eke fractional gains from the existing almost time expired signalling on the line. I appreciate there is definitely a case for commonality between 4LM and the Piccadilly line, however there are a few things to consider why a deal hasn't and probably won't be done. Firstly, TfL is very keen not to put themselves into a position where they are reliant on a single supplier, and, as a public sector organisation, they're not generally permitted to single source either. by the end of 4LM the split between suppliers will be: 1/11 lines (Piccadilly) LU designed and largely able to self-support for spares. 2/11 lines (Bakerloo and Waterloo & City) LU Designed with some reliance on Siemens for spare parts. In the case of the Waterloo and City line, the original design was done by Siemens (Westinghouse) but extensively modified by LU. 2/11 lines (Central and Victoria) Siemens (Westinghouse) designed, with significant reliance for spare parts (and in some cases system support and upgrades). 6/11 lines (everything else) Thales designed with almost 100% reliance for not just spare parts but also system support and upgrades. I imagine there would be considerable resistance to the idea of TfL putting any more of their eggs in the Thales basket - especially considering the possibility that Thales may well be taken over by Hitachi ( though I note it it currently under review by the Competition and Markets Authority) and the potential vulnerability of Thales' product line should such a takeover occur. Secondly, whilst the Piccadilly line signalling has now largely exceeded the original design life of 40 years, the principles of LU wayside signalling haven't massively evolved in those 40 years. The components are more or less the same and could be replaced on a functionally equivalent basis for a further 20 years without difficulty. The original signalling control system has been recently replaced with a system which can be supported for the next 20 years. If there is a desire to save money (which there undoubtedly is thanks to the Covid funding crisis) it could be argued that limited public funds should be spent in the most efficient way - which is to undertake targeted spending on the areas which need it for either asset condition or capacity constraints, rather than a wholesale replacement of the signalling.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Aug 18, 2023 16:30:30 GMT
I think there are several ways it could have been described - broken down train (without reference to what sort of train), or even 'late finish of engineering work' bearing in mind it's an Engineer's train. I don't think needlepoint precision on the description was either necessary or helpful for most passengers, though it's the sort of thing we (as enthusiasts) often take great interest in.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Aug 13, 2023 19:40:28 GMT
24tph = 150 seconds interval, 27tph = 133 second interval, so need is to despatch each train 17 seconds faster. How will further time be saved? Can more platform staff chase passengers along, or will more passages off the platform be needed, or will more home signals allow trains to get safely closer together? Exactly. Interval, or headway, consists of run time from from the sighting point to the signal, through the signal's control area, to when the back of the train passes out of the control area. The running time through the control area includes, where appropriate, dwell time - so home signal headways are almost always greater than starting or intermediate signal headways. The location of Kings Cross, at the end of a long, reasonably high-speed inter-station run, means signal overlaps on the home signals need to be longer to cater for the higher speed - plus there's the added complication of the crossover a short distance beyond the platform. All these things conspire to give the home signals a quite large headway. So part of the solution is either to get better at managing the dwell time, which I would suggest isn't going to be enough to get the time needed, or make some changes to the signalling, which also won't achieve the improvement required on its own. In theory, improved acceleration and braking performance helps but in reality train performance will be limited to match 1973 stock as the signalling is mostly designed around that stock's acceleration and braking characteristics. A number of changes were made about 20 years ago to try and make the overlaps protecting the crossover more robust - but it's likely that either some additional signals, some more speed control, or a combination of both will be required to further improve the headway.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Aug 12, 2023 10:46:58 GMT
Quite simply every line has a capacity in terms of trains per hour. The pinch point is the location where the signalling has the lowest capacity, and becomes the limiting factor for the overall service that can be operated. Once you try to run more trains than the line can handle, it becomes inevitable that a queue of trains will form trying to get past the pinch point.
From memory Kings Cross WB cannot handle more than 24tph whereas the rest of the line can manage a bit higher (around 27tph, I think).
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Aug 11, 2023 18:48:40 GMT
I agree with Chris - it's almost certainly passenger throughput. The Victoria line resignalling (to 36tph) has highlighted that at certain key stations, such as Victoria, it's impossible to clear the platforms from one train before the next arrives. I expect that in coming years, the passenger throughput through a station will become the limiting factor on capacity, rather than rolling stock or signalling, in many more places.
With regard to Holborn it cannot be signalling capacity that restricts things, as Holborn isn't the pinch point. On the WB Piccadilly the pinch point is Kings Cross.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 30, 2023 20:00:18 GMT
I'm going to guess at between Dagenham East and Elm Park.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 27, 2023 6:42:31 GMT
Westbourne Park for the main.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 26, 2023 20:09:58 GMT
[People who use wheelchairs also prefer paper travel cards - especially if they have self-propelled wheelchairs because they often need to stop and rest their arms during the journey. Too often this need (to stop and rest) sees them breach Oyster journey time limits. Has there been anything to suggest this is actually the case, or is it something you perceive could be a problem? I don't think I've ever heard of this being a problem before - possibly because in most cases, those wheelchair users living in Greater London would have the use of a Disabled Persons Freedom Pass.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 25, 2023 15:59:27 GMT
Of course, that doesn't mean that it's even been considered for LU (or any other railway). That's the point I was getting at; if the introduction of such technology is realistically in the pipeline for LU.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 24, 2023 21:22:00 GMT
This will only change when 'be here' ticketing is introduced, because it will follow (track) us through our entire journey and be able to charge for actual travel. Whether passengers will welcome that degree of surveillance / tracking remains to be seen. Is this something that is on the horizon or a figment of your imagination?
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 24, 2023 20:50:15 GMT
Used to be 70 north of Harrow North Junction to Amersham. Short of recalculating every overlap I'm not sure what they were signalled for, but I think they might not be considered adequate by today's requirements.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 23, 2023 19:26:03 GMT
assuming LUL does not have an agreement with Chiltern for someone to install CBTC in their fleet. As my learned colleague d7666 has posted, there's no agreement to fit CBTC onto any main line stock. Even if there was, the agreement would not be with Chiltern but with the Rolling Stock Leasing Company who actually owns it. ]Some of the Chiltern Turbos still regularly reach 75mph and the GWR turbos still regularly reach 90mph. But if that is the case then why are the Chiltern Railways services also limited to 60mph on LUL tracks? Braking distances and overlaps for 60 mph ? Most of the signalling in that area would have been designed to the 1955 overlap formula - a 60mph overlap on level gradient would work out at about 476m and for 70mph would be nearly 650m. Using the current 2008 formula would result in a slightly shorter overlap. Others who are more experienced in overlap calculation than I am might suggest that some of the existing overlaps are probably a little short for 60mph today, but part of the justification in a multi-aspect area could be that it is unlikely a driver will fail to react to previous cautionary aspects and trip at line speed. (Though obviously this did happen with the incident at Chalfont a few years ago.) The braking distances from the first cautionary aspect to a red tend to be quite generous and would appear to have been calculated on a very low brake rate appropriate for steam traction, possibly with some additional allowances for brake build-up along the train (the standard Newton's laws of motion equations assume deceleration rate is constant and instantaneous). There are, of course, other factors which would need to be considered before permitting an increase in speed - track is designed for specific speeds, particularly around curves and any increase in line speed would need to be assessed for things like cant.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 13, 2023 18:28:13 GMT
The lower image is East Acton. Not sure about the upper.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 10, 2023 19:22:06 GMT
One of those situations where Companies House is a very useful website!
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 10, 2023 18:39:01 GMT
The outdoor sections of the Central line no longer need the air main; I don't know if it's still kept pressurised though.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 10, 2023 18:25:32 GMT
Thanks for that I did a search but that company did not come up mostly overseas companies. KGM became KME (Kent Modular Electronics) in 1990. They're still trading - I remember them supplying new monitors for the control desks at Baker Street in the early 2000s. www.kme.co.uk/
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 10, 2023 18:21:48 GMT
That's exactly what they were!
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 9, 2023 17:38:17 GMT
I wonder if it might be Croxley, but I'm not 100% sure.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 8, 2023 11:33:35 GMT
A Acton Main Line, B Roding Valley.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jul 4, 2023 21:06:14 GMT
blue handrails visible in reflection and took it to be Piccadilly line, also cable runs confirmed this, just looked a Google maps to locate similar buildings and knowing level of the line to adjacent roads. I often use the cable run to guide me too. I had a feeling it was the Uxbridge branch, but wasn't sure where!
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jun 19, 2023 19:53:10 GMT
Oh yeah, I can see the TTC signs now!
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jun 19, 2023 16:31:42 GMT
I think No. 4 might be 30th Street, Philadelphia.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jun 16, 2023 18:36:53 GMT
ALARP - As low as reasonably possible. Practicable, not possible.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on Jun 7, 2023 14:33:27 GMT
Inset 1 = West Bromwich Town Hall. I should have known that one, considering my grandparents lived on the same road...
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on May 30, 2023 19:49:32 GMT
At Shepherd's Bush Market, there's no way that for 99.9% of passengers it could take 3 minutes to get from the entrance to the platform. Lifts. The transit time has to be for the reasonably slowest individual. There aren't any lifts (or a footbridge) at Shepherd's Bush Market. Just a set of stairs from each platform down to the ticket hall.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on May 23, 2023 14:57:48 GMT
Looks like Willesden Green, but I could be wrong.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on May 12, 2023 17:02:16 GMT
My personal thought is that it is Sub-Surface, as the Northern Line had NMAs (Northern Migration Areas), But the Jubilee TBTC migration didn't have JMAs did it ? No, they were simply known as J1 to J5. I have confirmed today via two independent sources that the S does indeed stand for SSR. It's only taken me four and half years!
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on May 11, 2023 20:17:26 GMT
I think the main is South Ealing.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on May 8, 2023 18:00:26 GMT
There couldn't have been many as High Street Ken was mostly underground. The last survivor was FRED1510 which wasn't far from Earl's Court.
|
|
Tom
Administrator
Signalfel?
Posts: 4,104
|
Post by Tom on May 6, 2023 22:35:05 GMT
some of those acronyms expanded: SMA = Signal Migration Area What the 'S' stands for is debatable. I've heard Signalling, System, Sub-Surface, and Seltrac, all of which could be perfectly valid. My personal thought is that it is Sub-Surface, as the Northern Line had NMAs (Northern Migration Areas), though I probably ought to check what the contract documents say it is. In the old days we would have simply called it Stage 1, 2, 3 etc., which would have been a lot more straightforward!
|
|