Line upgrade

We are now less than a year from planned arrival of the first new train, and have yet to see news of progress with depot reconstruction. The unique formation of these trains requires lifting of an entire train with jack points at new spacing, so new facilities are required. These were planned for the new train's arrival, but an early six-month delay due to Covid left a problem which has only grown with programme slippage. The production of the new trains is reported to be on schedule, although we have only heard of construction of the first three cars, one of each type.

South Harrow new sidings were delayed, but are now complete, and with Northfields new sidings can accommodate trains moved from a quarter of Northfields Depot to allow for the planned reconstruction. This has yet to happen. At Cockfosters, additional sidings were to allow space for similar works, but works have not been reported. Any updates on planned works?

What would be the reason for the limit on throughput with the current station layout? I didn't think the track layout was affected by the plans, just work on step-free access and much else away from the platforms.

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.

What does, and paraphrasing here, 'signalling is a pinch point', mean?

Kings Cross Picc westbound platform sees demand from the mainline station above meet passengers from the north end of the Picc line changing to other lines for the City and other mainline stations. This is mainly towards the front of the platform.

24tph = 150 seconds interval, 27tph = 133 second interval, so need is to despatch each train 17 seconds faster. The promise is for 27tph with current signalling and the new fleet. I presume the new trains will brake and accelerate better than the current trains, so saving some seconds at each station stop. 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? There are only a few more years before this is due to happen now!

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.

Assuming the 1973 stock pair of end doors are equivalent of a double door, which they are not, there are 17 double doors down a six car train (middle cab units excluded) compared to 18 down a 2024 stock. So only one extra, but real double-doorway instead of adjoining pair of single doors will also make a difference. They will be wider doors also, but little stand=back area may negate that with people standing either side of the opening.

Apart from battery & sleet locomotives the oldest stock I worked on was 35TS prototypes which worked the Epping-Ongar shuttles.

One Standard Stock DM with that door arrangement still exists - if ever the Standard Stock heritage train becomes advanced enough to carry passengers then some of them might even be able to experience this.

As for experience of a century of tube trains, I think I might qualify for this accolade. If not yet then 'soon' (by 2026).

I've travelled on Standard stock trailers in normal daily passenger service on the Bakerloo and Central lines. But not sure about DMs (I think not).

Possibly also Q stock - they went when I was 11 so if I did travel on them then I would have been too young to know it.

I do recall seeing an R stock train with the guard using a rotary door control lever (not buttons). Not even having a still photo of this is partly what influenced me to film a guard in action on the 1962ts trains shortly before they were replaced.

Photos clearly shows lack of stand-back space for passengers intent on staying by the door. With a passenger either side and one behind the central pillar, it is clear that one would have to slide sideways through the remaining gap. This was common at peak times on the Central Line. I believe the new Picc trains will have little stand-back space. Certainly less than the current trains. Also the internal label 'do not alight from moving train' always fascinated me. How could you do so when the guard didn't open the doors until the train was at a platform. That must have been a standard label used when hand-worked door trains were still in service. And yet it remained in use into the 1970s IIRC.

districtdavesforum.co.uk/post/510507 lower photo shows small stand-back area behind Sadiq Khan on design mock-up; link shows 1973TS stand-back area to fit suitcase. 

Whilst the passenger dynamics of the new trains is definitely worth assessing (and I assume has already been) this thread is of course about the "Line Upgrade" so it is important not to overlook passenger dynamics within the most overcrowded core section stations. So yes some people will always lurk by the doorways and avoid "moving down inside the car" despite endless requests from platform staff. But this is not the underlying problem with line capacity.

The TFL paper linked above by Jimbo reports that there are several core area stations on the Piccadilly where inadequate station design (entry/exit capacity) is the real limiting factor rather than boarding issues with the existing trains. Providing passengers a more consistent pattern of doors on trains may help slightly but won't deal with the issue where everyone is bundled up at one end of the platforms because that is where they need to go to enter/exit or interchange.

Whilst we all like to ride around on nice new trains - I have a feeling TFL now need to look at (and fund urgently) making physical changes to improve passnger flows in the worst stations. I have a feeling that despite being every bit as important to "upgrading the line" it seems that significant investment in things like making boring structural changes to bottlenecked stations (just like reworking the Northern Line Bank station) rarely have the political kudos/visibility and are being sidelined for more sexy ribbon cutting projects.

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.

That sounds like a tough ask to shave 30 seconds off the headway. I suspect it might be doable at some stations, but it'll still leave a 27tph pinch point at places like Kings Cross.

A lot of the auto sections are laid out with two home signals and blockjoints positioned to allow an easy installation of a third home signal should the need arise.

link provided above seemed to think there were work arounds for 33/36tph at all but Holborn, where a new entrance would also provide a sub-station under the new booking hall to power the new trains on the Picc and Central lines.