A long-running signalling upgrade on the London Underground is starting to show results as the latest timetables show faster journeys on some trips. The four lines modernisation project is replacing antiquated signals across the entire sub-surface part of the Underground – that’s the District, Circle, Metropolitan, and the Hammersmith & City lines.

The upgrade has been underway since 2016 with signalling upgrades switching on in stages, but earlier this week, the first public-facing changes occurred that show the impact all those years of work will have. The latest timetables used for the Underground are showing faster journeys and a more refined calculation of the timings, initially along the H&C and parts of the Met lines.

Previously the elderly signalling could only allow timetables to have timings resolution to the nearest half-minute, but the current stage of the modern signalling upgrade has already improved that to every quarter minute. So the new timetables are seeing the ¼ and ¾ symbols in them for the first time.

Improving the signalling resolution to the quarter minute means that they will eventually be able to run trains a bit closer together so they can start increasing the number of trains per hour on the lines, and more trains per hour means more capacity on the railway to carry passengers.

From this at Edgware Road (c) TfL

To this at Hammersmith (c) TfL

Journeys are also getting quicker

In total, looking at the off-peak timings between Barking and Hammersmith, that journey used to take 58 minutes, but now takes 54½ minutes. Doesn’t sound like a big saving, but in an idealised scenario, that train might make 20 trips a day, and those few minutes saved add up to the point that would allow them to fit in an extra train trip each day. Obviously, it’s vastly more complicated than that, but it gives you an idea of why faster trains means more passengers can be carried in them.

So while a person making a short trip between say, Plaistow and Whitechapel will see their trip a mere 30 seconds quicker, which is almost invisible to passengers, as each section goes live along the upgrade, progressively faster return trips along the entire line means more trains per hour will be possible when the upgrade is complete. It’ll also mean a much more reliable service, so fewer delays, an improvement that will be far more noticeable to passengers.

That’s how faster trains increase the capacity of the network — and incidentally why adding extra stations reduces capacity by slowing trains down, something that campaigners to reopen disused stations rarely factor into their calculations.

Comparing the previous and current working timetables on the Hammersmith and City line and selecting a few random sample of off-peak times, the journey time between Plaistow and Whitechapel used to be timetabled for 12½ minutes but is now 12 minutes. The trip between Whitechapel and Liverpool Street has dropped from 5½ minutes to 4¾ minutes, and so on until trains reach Hammersmith.

Likewise, the Metropolitan line gets faster as it shares some of the core tracks, and the signalling upgrade has been rolled out further along the Met line already. Comparing the working timetables (341 vs 342), the average journey time from Aldgate to Wembley Park shrinks from 29½ minutes to 27¾ minutes.

The section between Rayners Lane and Harrow-on-the-Hill is also quicker.

No one is going to be changing their alarm clock thanks to these changes, but it’s the first public-facing change to the service after years of preparation works, and as the roll out continues, there will come a point where they can run more trains during the peak hours — and that means you’ll have more chance of getting a seat.

Works are still ongoing to roll out the upgrade to the rest of the network. In May the new signalling went live along part of the southern half of the Circle line, while works at Neasden are preparing for upgrades in that part of the Met line.

It was predicted in 2019 that services would start to increase in frequency from 2021, and although they’re not running more trains yet, that’s more an effect of the pandemic than the signalling. The project was due to complete in 2023, although that’s also been pushed back by the financial impact of the pandemic.

It’s not been a project without its problems though, as it should long since have been completed, but the original contract awarded to Bombardier was later cancelled in 2013 and Thales took over the project, and that added years to the project timeline.

Apart from signalling, a lot of supporting systems need upgrading from extra power to run more trains more often to increased maintenance capacity as trains that run more often tend to wear out faster and improve stabling for more trains, a brand new signalling control centre at Hammersmith, and of course, training for staff to use the new systems.

When completed, the programme will allow TfL to operate 32 trains an hour in the central section of the sub-surface lines, a 33% increase in peak-hour capacity – which equates to space for an additional 36,000 passenger journeys per hour.


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  1. ChrisD says:

    They still cannot achieve the headways that the underground ran to in 1929, nor can they match moscow wit’s theh antiquated signalling system.

  2. Ryan says:

    The first public-facing improvements thanks to 4LM were in fact accurate departure boards on platforms (and in apps).

  3. Chris Rogers says:

    The Met line resignalling has been going on for years, literally, and I’m only glad I don’t use it much now, having suffered then. The Northern too was hammered by closures a few years back for its works; we were promised significant improvements but when the posters went up trumpetting the completion it was notable that those benefits were triply caveated – some trains, only in peak, ‘up to’ etc.

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