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Post by greatkingrat on Apr 26, 2024 20:00:52 GMT
Would Richmond be able to cope with 12tph plus the Overground?
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Post by jimbo on Apr 26, 2024 23:44:05 GMT
I think Overground to Richmond is only 4tph. I have seen no concerns about current signalling coping with an extra 4tph on that branch. Only concerns expressed for extra 4tph to Wimbledon branch.
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Post by A60stock on May 1, 2024 10:20:27 GMT
Going back to the Met line area, SM8/9, once these are done, I am hoping that the max speed trains currently achieve on the fast routes, routinely around 62-65mph (especially northbound between Finchley road and Wembley Park and Southbound fast Moor Park - Harrow - Finchley) are not slowed down. I am taking example from from the route between Finchley and Baker street which now seems slower overall than pre re-signalling.
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Dstock7080
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Post by Dstock7080 on May 1, 2024 11:23:43 GMT
The maximum speed currently permitted between Finchley Road and Amersham is 60mph. Temporarily in CBTC the maximum is 56mph, because of issues with tag reading, this hopefully will be resolved before SMA8-9 are commissioned, the maximum would then be 62mph.
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Post by A60stock on May 1, 2024 14:15:24 GMT
Does the reason above also have anything to do with why trains do not run as fast as they could between Finchley and Baker St (particularly on departing Finchley Road)
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Post by starlight73 on May 1, 2024 21:09:40 GMT
Dstock7080 , I’ve tried to convert your post into a table - let me know if there are any errors, or feel free to edit this post directly. | Max speed (mph) |
| Station | Conventional signalling | CBTC | Finchley Road | 30 | 12 | (approach to…) |
| 35 | Swiss Cottage crossover* |
| 19 | | |
| 31 | (approach to…) | 35 | 47 | Marlborough Road former station | 30 | 33 | Lords former station | 40 | 48 | Bridge over Regent’s Canal | 25 speed-controlled trainstop | 24 | (approach to…) | 20 | 21 | Baker Street |
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*trailing crossover, i.e. from northbound to southbound track when travelling southbound It’s noticeable that CBTC often adds a few mph to the speed limit than conventional driving, since speed limits are to the nearest 1mph rather than rounded to 5mph. I’m wondering if what A60stock described could be CBTC driving more economically if the train is early, or the path into the next station isn’t available? Edited to clarify: a human driver would drive at the maximum permitted speed until they see a yellow or red signal, whereas CBTC could??? slow down the train earlier to reduce the chance it will have to stop at all (that’s a question, I don’t know if it’s true or not)
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Post by jimbo on May 1, 2024 21:16:42 GMT
CBTC can afford to be more generous with limits since they are verified and enforced by the system. That is not generally the case with conventional signalling, although a speed-controlled trainstop will do that.
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Post by t697 on May 2, 2024 19:20:50 GMT
The SSR CBTC does drive more economically if the train would otherwise be early. Another place the difference is fairly obvious is King's Cross - Farringdon both directions where full performance is notably faster than the dawdling speed when running to time or early.
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Post by A60stock on May 3, 2024 15:37:37 GMT
I did think it might be something to do with that, however, no matter when you travel, be it off peak, rush hour, late night etc, the departure leaving Finchley is very slow until a little while after the Swiss Cottage crossover. I am sure that pre CBTC, this was not the case. The same applies to just after you depart baker street going northbound, where it seems much slower then it was pre CBTC.
I compared two videos of a northbound journey, baker street to Finchley road (drivers eye view), one being a current video depicting an s8 stock doing the journey in 2023 and the other being an A Stock doing the same journey in 1992 (great watch btw). I put these two videos next to each other to see which one got to Finchley first. Now, unless the video in 1992 skipped part of the journey, the A stock got there a minute or so before the s8 stock did. I cannot understand why this is slower****. It has been 4.5 years since cbtc came in.
By contrast, the jubilee line looks like an ideal example of running automated signalling to its peak, where the trains are generally quicker almost everywhere then pre automation.
****I agree that in all other areas where CBTC is on the met, it seems to be quicker than under conventional signalling and I am generally happy it replacing the old and outdated signalling. However, I just hope we dont see trains being slower in other areas, especially on faster sections.
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Post by t697 on May 3, 2024 16:40:59 GMT
Accelerating rate out of Finchley Road SB may currently be set to the most restrictive for no specific reason or so there's no wheelspin on wet rail whatever the weather.. Perhaps someone else will know. Pre-ATC the accelerating rate from the platform was the T/Op's choice.
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Post by starlight73 on May 3, 2024 17:36:36 GMT
DStock’s post does back this up - there is a lower speed on leaving Finchley Road station (12mph) and then 19mph on Swiss Cottage Crossover (I presume this is the normal route and not when the crossover is being used?) Incidentally Colin mentioned a similar thing up-thread where CBTC is slower over Embankment crossover than manual driving Ultimately the maximum speed limits set up within the CBTC system are provided to Thales by the track engineers responsible for the given section. It seems that the speed limits given to Thales can vary from what they were under the legacy signalling system. […] Anyway, we have a similar oddity on the District approaching Embankment w/b where under the legacy system we ran over the crossover and into the platform at line speed (35mph) whereas under the CBTC signalling system the train slows to 20mph. No rhyme or reason as to why! Could the Finchley Road case be a temporary speed restriction related to track? Update: I’ve tracked down a quote from goldenarrow which seems to explain this Finchley Road southbound situation: Quite indeed. Although in this particular case with regards to the SB departure of Met line trains from Finchley Road is surely just a case of allowing the train to depart quicker (i.e. the same pace as they did when it was under manual driving). It looks as if the system is set to crawl upon leaving Finchley road SB for some strange reason, so its got to be a case increasing the speed limit on CBTC in that section when all is clear. There's a temporary restriction leaving Finchley Road on the SB to address some reliability issues at the SMA 2 boundary when commissioned in Sept 2019. I anticipate that this should be resolved when CBTC extends north of Finchley Road as part of SMA 8. I too share Colin 's reservations on what CBTC can actually do for the SSR. Most of the recovery from late running I've experienced on the Met City service so far can be attributed more to short and snappy changovers/stepping back at Aldgate.
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Post by xtmw on May 3, 2024 18:34:05 GMT
I wonder what drivers opinion's are driving in protected manual on the SSR lines? Any C&H/District/Met Op's want to add a few lines on how they feel about it as I know TBTC insists on a full stop if you overspeed
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Dstock7080
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Post by Dstock7080 on May 3, 2024 19:35:53 GMT
Perhaps I can comment as a recently retired District Train Operator, who commenced my career working CO/CP and R Stock, the CBTC system has its foibles and is generally very good doing what it is designed for in normal operation.
PM Protected Manual is quite difficult get on with, as you (in my opinion) constantly looking down at the SID Signal Interface Display which is the only reference for the state of the road ahead. There are audible prompts for potential overspeed violations etc. and changes in status which can be quite distracting. All changes in maximum speed are mandated by the system and the driver has to react to these promptly to avoid an emergency brake, especially when the limits are reduced. Entering a platform under conventional signals the driver is just trying to align the cab with the stopping markers at the far end of the platform. Under PM driving the system is continually warning about potential over-speeding when entering a platform and reducing the maximum permitted speed every few seconds. This can be disconcerting while the driver is looking down and then up to see the progress into the platform.
Until the recent publication of mandatory PM driving at certain locations and at certain times on SSR it has been the individual driver choice as to whether conduct the train in ATO or manual, many of my former colleagues preferred not to use PM driving as it was perceived as being too much faff to bother with!
Perhaps, making it ‘awkward’ to operate was the aim, therefore keeping most trains within the system.
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Post by xtmw on May 3, 2024 20:29:02 GMT
Happy retirement, Dstock7080 may it be a long and happy one. You can finally put your feet up and rest! (Maybe I would have noticed you retired if I looked at your signature ) I assume it's driving in PM on Sundays in certain sections? I guess it'll be alot of 'defensive driving' when in PM as it obviously looks like a pain to deal with. Bring back the tripcocks !
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Post by Dstock7080 on May 3, 2024 21:02:33 GMT
I assume it's driving in PM on Sundays in certain sections? I guess it'll be alot of 'defensive driving' when in PM as it obviously looks like a pain to deal with. Not quite that simple:
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Post by jimbo on May 3, 2024 21:18:48 GMT
By sitting observing whilst the train operates in CBTC, the driver can relax but loses skill over time. By choosing to drive, the operator risks error and disciplinary action as a result. This is all monitored by the system. Unless it is compulsory at times, there is little incentive to take control of the train.
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Colin
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Post by Colin on May 3, 2024 23:52:40 GMT
I wonder what drivers opinion's are driving in protected manual on the SSR lines? Any C&H/District/Met Op's want to add a few lines on how they feel about it as I know TBTC insists on a full stop if you overspeed As Dstock7080 says, driving in PM is quite disconcerting. Because it's a moving block style system you never quite know what it's going to do next. It'll drop the speed limit on you and expect an instant response - if it doesn't get one it'll throw overspeed imminent warnings, then before you know it the emergency brakes have been applied. I find as an experienced driver, it's doubly hard to drive in PM because I knew where I could coast or motor, what the line speeds were in any given area and how far it was to the next signal (therefore how far I was clear to drive my train). With CBTC I only know what the in cab signalling is telling me......and again with the moving block nature sometimes the target speed and distance to go are constantly changing quicker than my brain can compute the information. I hate PM driving and I can confidently state the vast majority of my colleagues hate it too. However, with my instructor's hat on, I find trainee's get on with PM driving quite well. Because they don't know the line they find it easier to go with what the system is telling them as they don't know any different.
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