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The second stage of the Four Lines Modernisation (4LM) has been successfully implemented. Its a gradual introduction of the SLM’s CBTC control system across the sub-surface lines as another four years will ensure before it is fully implemented. Traditional colour light signals, trip cocks, air operated equipment and signal cabins and the likes are its victims. There’s another side to it and that is the end for one particular style of signal. These are the coffee pot signals which have been in use more than a hundred years. They’re not 100% out yet though!

If you do not know what coffee pot signals are I have written about them at length here and here. And for those who do know what they are, well, despite the 4LM’s successful introduction to Stages 1/2, the last few remaining examples of these signals are still in use – at least one or two being far more than a hundred years old and still operational! When we think of signals such as those on the Piccadilly Line dating from its modernisation in the 1930s and which are still in use, these coffee pot signals go back a further thirty years.

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Example of a coffee pot signal above the platform at Liverpool Street in 1912.

These considerably ancient railway signals should have gone years ago when the previous Sub-Surface Upgrade programme, and the earlier one with the PPP initiative, had been underway. The debacle behind these earlier schemes and their cancellation, along with the delays in implementing the present scheme has ensured the remaining coffee pot signals have seen more than another decade of use.

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Baker Street’s coffee pot signal in happier days.

I do not know what Metronet (the PPP initiative) or Bombardier (the SSUP initiative) had planned fully in terms of ATO for the sub-surface lines, because neither of those schemes were fully realised. Bombardier had built the new Hammersmith control centre and some equipment rooms but that is as far as it went. Under Thales at least we have been able to see its full development and implementation and certainly how it is being rolled out across the sub-surface lines.

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The same signal under wraps on the first day of ATO train operation.

I have listed elsewhere the remaining coffee pot signals but do so again here. These were (prior to 4LM 1/2) at Baker Street (1), Great Portland Street (2), Euston Square (2) Barbican (2) and Liverpool Street (2.)

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Great Portland Street’s westbound coffee pot repeater. (It wasn’t really of much use, being right next to this very bright repro 1863 style light – which too made it quite hard to get decent photographs of the signal!)

Under 4LM the earlier SMA 0.5 and SMA 1 phases had entailed no coffee pot signals so SMA 2 is the first section which the coffee pot signals were encountered. There are five in this section however one of these, the eastbound at Euston Square, is being kept operational until SMA3 is introduced in February 2020 (if all goes to plan.)

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The same Great Portland westbound repeater under wraps.

Those that have been retired are that on the westbound platform at Baker Street, two in each direction at Great Portland Street and one at Euston Square. This is the initial four (and the smallest complement) of coffee pot signals to be phased out, leaving the larger number of such examples (five) to come next on SMA 3 (King’s Cross eastwards.) It means the second batch including the oldest examples still at work will last into early 2020.

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Great Portland Street’s eastbound signal with its green light not working. It was curiously repaired just a week before 4LM was activated.

There has been every expectation these last couple of months that these signals will be retired. They are not absolutely crucial to the operation of the railway and haven’t been for quite a few years but taking them out requires substantial re-wiring and so its probably been best to just leave them. Nevertheless they have had their uses at stations where platform staff were required at busy times – because the staff could see the state of the train signals if the main signals are obstructed from view by passengers or line of sight. As of now any platform staff will instead have to rely on the train CBTC indicators.

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The yellow worked of course!

In these last couple of months up to Stage 1/2 if the yellow repeater light failed the bulbs were simply not replaced. This has been observed at Barbican, Great Portland Street and Euston Square. The eastbound platform repeater at Euston Square lost its yellow a bit later than the other two. That at Great Portland Street was a bugbear to fix as it is extremely high up and also right over the tracks – yet some engineer fixed the green aspect back to a working condition just one week before 4LM was activated! Bizarre.

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Like the others, this too is now under wraps.

I have also noticed instances of the more modern colour light signals in the weeks approaching the ATO second stage’s implementation where blown bulbs were not replaced either. One example of this is since mid August the eastbound platform repeater at Baker Street only ever showed a yellow. The green aspect was never repaired.

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Euston Square’s westbound coffee pot at work on its final day, 30 August 2019. This is a section of tunnel on the original 1863 route that has had consistent leaks – and it has also been populated by pigeons!

Despite all these bulb failures there has been one signal that bucked the trend. The eastbound at Great Portalnd Street had its bulb for the yellow signal replaced just a week before 4LM! This is the most difficult of all the blown signal bulbs to replace thus one wonders what the reasoning was in replacing it.

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Euston Square’s westbound coffee pot under wraps.

The only coffee pot signal left at work on the original 1863 section of the Metropolitan Railway happens to be that on Euston Square’s eastbound platform. Its a curious situation because its a possibly 100 year old signal giving an aspect to fully automated trains entering the station so really one wonders what the reason for its retention was. I suppose seeing there was a station starter signal its repeater also had to be also fully working but given that the yellow served no purpose really the failed bulb in that wasn’t replaced.

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Euston Square’s coffee pot repeater at work on the first day of ATO operation.

There is a quite remote possibility the coffee pot signals could once again work, but only if any substantial failures hits the newly activated 4LM ATO sections. Once the CBTC is initialised there is a migration period (I think its two weeks) and if any major issues occur this allows engineers to restore the old signalling system whilst the circuits/software/train onboard computers/wi fi points etc are investigated.

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Euston Square’s eastbound coffee pot signal is the only example working within the current phase of ATO on the sub surface tube.

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