Wimbledon signalling

[djw1]

Multiple times across the last few days the District line has been suspended / severe delays to Wimbledon due to a signal failure at Wimbledon Park.

Is this going to be another repeat of the signal issues at Southfields last year where it takes forever to get resolved?

Given all of these issues, do you think that it’s now more than ever justified to bring back the planned CBTC signalling? Would they ever consider rolling it out without the ability for national rail trains to use the track up to East Putney?

 

[Mojo]

The fault you’re talking about was resolved by NR early afternoon yesterday.

In an ideal world the entire line would be handed over to LU properly, with LU also operating the signalling and traction current and with trains operated in line with LU rules and procedures. NR trains could still operate over the line subject to their drivers receiving the appropriate training (such as on Chiltern which run down the Met). I don’t see this happening though.

 

[Dstock7080]

This particular fault, a defective block joint, would still exist if CBTC underlay was undertaken down to Wimbledon as track circuiting would be required (not as on the MET Harrow-Amersham main, Rayners Lane-Uxbridge).

(not - added)

 

[GFE]

Note the solution used on the Met branches (to handle non CBTC equipped trains) will use Axle counters instead of track circuits.
The same seems to be the case with NR policy of conversion to "digital signalling"
Axle counters don't need Insulated block joints, electrical connections to rails or continuity bonds around rail joints (which are common failure points)

 

[bluegoblin7]

In this case though the fault absolutely would have still occurred under CBTC - the solutions planned for the Met top end and Wimbledon branches were not the same.

The Met is using a CBTC underlay - that is, the core signalling logic and interlocking is driven by the CBTC system, with colour lights and train stops added as additional features. LUL’s Seltrac implementation uses axle counters as a fallback for train detection through points and crossings anyway, there are simply more of them added to create rudimentary block sections for the detection and operation of ‘alien’ trains.

The Wimbledon (and Richmond) branches were planned to use a CBTC overlay - the existing interlocking would be retained as the primary signalling circuitry, with the CBTC system taking its data from this and communicating with the trains in the usual manner. This would therefore retain the existing track circuits and block joints, and never offered any major benefits over just retaining the existing colour lights - even CBTC trains would be restricted to the existing signalling fixed block sections.

Very much agreed with @Mojo that the best solution all round would be for the branch to properly transfer to LUL control, which would allow for the same solution as on the Met to be implemented.

 

[eastrail]

I think I heard that the 1938 stock can still run on the Met after CBTC goes live. I assume it will use the same underlay as Chiltern trains and be limited to the Harrow-Amersham main line?

 

[bluegoblin7]

Yes, any train with fitted with a tripcock can operate on the Main Lines only, plus some selected crossovers and sidings, between Harrow and Amersham and Rayners Lane and Uxbridge following CBTC commissioning.

There are, however, logistical challenges in getting such trains on and off this part of the line, as well as overnight stabling. Not impossible, but not as simple as it is today.

 

[swt_passenger]

Multiple times across the last few days the District line has been suspended / severe delays to Wimbledon due to a signal failure at Wimbledon Park.

Is this going to be another repeat of the signal issues at Southfields last year where it takes forever to get resolved?

Given all of these issues, do you think that it’s now more than ever justified to bring back the planned CBTC signalling? Would they ever consider rolling it out without the ability for national rail trains to use the track up to East Putney?

No. Use of the track for ECS movements is regular and is essential to SWR‘s operations to and from the depot. It’s not just the relatively few passenger services that are there for route learning.

 

[xtmw]

The west end of the District Line was descoped from the 4LM programme, on cost grounds, I assume as well as the technicalities of using a CBTC overlay

 

[GFE]

So the originally proposed CBTC overlay would add more kit to existing signalling so inherently less reliable?
I think they were looking at improvement initiatives to help maintainers, but if NR are the maintainers, the motivation/priorities/response time need work.

 

[Recessio]

When Wimbledon Park, Southfields and East Putney were transferred from Network Southeast to LU (for the nominal sum of £1) during privatisation in 1994, was any thought given to transferring ownership of the track itself?

And why was the implementation of CBTC planned to be an overlay rather than an underlay like on the Metropolitan? Is it just because it's still an NR line with NR signalling?

 

[Mojo]

When Wimbledon Park, Southfields and East Putney were transferred from Network Southeast to LU (for the nominal sum of £1) during privatisation in 1994, was any thought given to transferring ownership of the track itself?

The track itself *was* transferred to LU. It is an LU asset and maintained by LU’s track teams, similarly for the physical infrastructure surrounding it (fencing, bridges, etc) which are all looked after by LU.

 

[Dstock7080]

When Wimbledon Park, Southfields and East Putney were transferred from Network Southeast to LU (for the nominal sum of £1) during privatisation in 1994, was any thought given to transferring ownership of the track itself?

And why was the implementation of CBTC planned to be an overlay rather than an underlay like on the Metropolitan? Is it just because it's still an NR line with NR signalling?

I don’t think NR wanted to give it up at that time as they had just modernised the signalling with the WARS scheme.
Yes, NR didn’t want to alter their signalling so it would have to be overlay.

 

[Recessio]

The track itself *was* transferred to LU. It is an LU asset and maintained by LU’s track teams, similarly for the physical infrastructure surrounding it (fencing, bridges, etc) which are all looked after by LU.

Oh I see - so is it an LU track with NR signalling? Or LU signalling but that is compatible with NR? I'm trying to understand why it is different from the Metropolitan situation

== Doublepost prevention - post automatically merged: 23 May 2026 ==

I don’t think NR wanted to give it up at that time as they had just modernised the signalling with the WARS scheme.
Yes, NR didn’t want to alter their signalling so it would have to be overlay.

Ah that makes sense, thank you.

 

[Dstock7080]

delete- fuller answer below

 

[bluegoblin7]

The Met uses NR-style four-aspect signalling - the actual underlying signalling principles are still to London Underground standards, which differ quite a bit from NR… although I appreciate this is splitting hairs somewhat. It is also somewhat irrelevant for CBTC given that it will be a brand new system and interlocking at the top end of the Met.

In summary:

Richmond (and north of Bakerloo): NR owned, NR signalled
Wimbledon: LUL owned, NR signalled
Met: LUL owned, LUL signalled

 

[Recessio]

Thank you all for the explanation, much appreciated!