new WTT58 19 September 2021

Ditto the entire line has been running under a 50 mph temporary speed restriction since 2013, though to be fair this is more to do with the trains than the signalling as such. I know 60 mph is still the aspiration, but no idea when it’s likely to be achieved. There have been a few speed uplifts recently - trains come into a few more platforms at full brake rate, and a few curves have had speed lifted (for example coming into Archway SB).

The Jubilee maxspeed is currently ard 55mph, can't the Northern do so too?

The original contractual requirement for the Central line resignalling was 36tph. I think most parties agreed it was not going to be achievable quite early on, the aim was then 33tph but I'm not sure even that has been realised?

Where I typed there 35 I couldn't remember if it was 35 or 36, and, ISTR this particular value was debated in DD some time ago, but I could not find it.

But I'll say again, 36 TPH contracted or declared capability of any signalling system is not the same as telling the public "we are going to run a timetabled service of 36 trains per hour" - because the latter means a sustained peaks service, implies for 3 hours in the core a.m. peak and again 3 hours in p.m. peak, both roads in each case. This was the point I was trying to make for the Northern to try and keep this on thread topic.

The timetable people always told me the practical Central capacity is around 32-33 TPH, and, AIUI, from THEIR planning rules view, the global throttle is the eastbound east of Liverpool Street. The problem is, to sustain a high TPH in each direction for 3 hours, you can't have one throttle on one one road, else the whole collapses. OK you could twiddle track circuits and go codes and block marker boards and sort that section out, but then the next most restricted area becomes the next throttle.

When I was working with the Wood Lane control system, there was a timetable that came in years mid 201x that gave a 34 TPH burst for a very brief period - about 25 min, on the westbound only, in the a.m. peak. It came in about 12-18 months before the Victoria self trumpeted it's increased peak to 34 TPH; we went well woopey-do, we being doing that for months.

The point is, that 34 TPH on the Central (I don't know if it is still there; it was something like 08:10 to 08:35 through Bank) was no way sustainable line wide, not even for one hour.

IIRC dwell times were significantly up at Bond Street and Tottenham Court Road because of increasing interchange passengers between Jubilee and Northern. The latter is relevant to this thread - if the Central dwell times goes up because of interchanging to\from the Northern, then the reverse is true, the Northern will also go up. This will equalise, even if it balances in the opposite peak, but it still remains. So, for example, you only need TCR on the Northern to get say only 1 sec extra dwell time for every peak train, and you've already lost 1\3 of a TPH path, and sure to lose more secs elsewhere, hence you get 31 TPH not 32 TPH.

There is one other difference between 95 and 96 stocks which does spring to mind - the 7th car on the 96 stock, which could have a bearing on things especially as it's a trailer car, which will of course alter the disposition of friction braking compared to a 6-car.

Good point(s). Actually obvious ones. Occams Razor ? Self smack wrists off topic.

I was wondering how Battersea was achievable without getting more trains. I think that is part of the problem with Underground extensions is that sourcing extra trains is always going to be a problem as it would be no longer produced, or wait until all new stock is produced. I think this also may have been a factor with the Jubilee line extension to prematurely end the 83 stock. Its District line counterparts lasted years later, even gaining a second moquette, then a third when they were fully refurbed.

Accepting your detailed post, I still believe 32tph was the promised public service frequency on the Morden branch, but how to prove that now? The TfL site had quite some detail, but long gone! I find that the line boss back in 2008 is reported as saying “The new system will allow 32 trains or more south of Kennington, but 30 are planned initially to allow recovery time, ..” source He would have approved this report, but my notes of the meeting are that he said that the new system will allow 34 trains or more south of Kennington, but 32 are planned initially to allow recovery time. 32tph is also shown in a diagram here as the expected service from December 2014.

It was always said that the extension would require five more trains, and that was built into its original cost. It is currently proposed to only extend half of Charing Cross branch trains there, so perhaps now only 2½ trains required. One was said to be released by more efficient maintenance procedures, which meant a new wheel lathe at Morden. The Mill Hill East shuttle train was only moving for 30% of its time, so a through service provides another 70% of a train. Tinkering of signalling, power, etc. to save a minute on line end to end run releases a train. The former stand time in the Kennington loop will instead be taken at the new terminus.

I'd not argue with that in the sense of internal technical discussions; that info I remember from briefings and one course when I was with tub lies.

But was it ever public ?

One of the reasons I remember this discussion - especially the bit about 32 or 31 or 30 TPH south of Kennington and what was theoretical against actually achievable - is because one wit at the time commented that if you put a human on board to detect train motion i.e. a guard on each train to release the doors, you'd gain not only 1-2 sec after wheel stop (because that's how long equipment takes to work out that dt/dx d2t/dx2 and d3t/dx3 have all come to zero and the train really is stopped) and then add the guard opening the doors just as the train is stopping rather than after it has stopped, you gain another 1-2 sec - and if you do that with every train at every station you get two more TPH than ATO.

Have to admit while I am familiar enough with Central ATO, and TBTC and CTBC, and worked in Wood Lane, Neasden, and Hammersmith SCCs, the Vic line ATO has by passed me completely; that's both the original 1967 system and the current DTG system. "I know nothing" as they say. My one and only visit to Coburg was after the Vic line had gone but when the Northern was still complete there, and my one and only visit to Osborne was a high level high speed look around no more. And to cap that, the Vic. line is my least travelled tube line, not even once a year, if that, and when I do it's usually only becasue something else is disrupted. Oops digression again.

Just because the line can theoretically achieve 32tph, does not mean it is wise to schedule it. Rolling stock available, probably insufficient for a start, and even if not, to put a timetable at absoloute maximum capacity is going to give you a 90% chance that on any given day by the end of the peak that the whole line is running late. It just does not make sense to do that. Every timetable should have some slack, somehow, for robustness.

The Victoria line is built to have trains running at high speeds. I don't think the central section of the Northern line and the distance of those stations are helping with that...

Camden is always going to be an issue for as long as a mixed service operates. The moment two trains turn up along side each other wanting to go down the same branch, the headway has been killed, and this is going to occur frequently during a disruption scenario. This is why on the Northern it is vitally important to chase minor late running or out of turn working, as if left alone at some point they will cause a conflict somewhere.

But even if crossing moves at Camden were completely axed I think the line would still struggle. It simply isn’t laid out as well as the Vic.