Over the next year, people using the London Overground will start to see changes, as the line prepares for a 25% capacity upgrade.

One of the few advantages of running trains that are just 4 carriages long is that adding just one extra carriage can massively increase the capacity of the service — but that doesn’t mean it’s a simple upgrade.

Far from it.


Not only are the stabling yards designed for 4-car trains, so are the platforms, the signals, the power supplies and even some of the track sections need working on.

Most of the works on the stations to lengthen them will start next year, but users of the Phase 2 extension to Clapham Junction may have noticed a large construction site just to the south of Surrey Quays station — and that is the first major works for the upgrade.

The Overground stabling facilities at New Cross Gate, which currently stable 21 four-car trains will be adjusted, but will only be able to house 13 of the new longer 5-car trains. Hence, the need for more stabling elsewhere.

An option to take over an existing site at Norwood would have avoided planning permission headaches, but as it is owned by Network Rail, would have left the Overground at the theoretical risk of later changes by the landlord. So, they took a bit of a risk and chose a plot of land that TfL already owned, and applied to build stabling yards there instead.

Hence, the Silwood Triangle.

This new site will become the home to another 10 trains and is conveniently close to the existing facility at New Cross Gate, where maintenance will continue to be carried out and trains washed.

Not the entire site is being taken over by the new tracks, as it sits in a slight depression, so tends to attract water from the local area which needs to be pumped away. Sometimes more water arrives than can be pumped away quickly, so rather than storing it in an underground sump, there is a local pond and mini-nature reserve.

There can’t be that many railway sites that need a life buoy next to them.


Construction work should be completed in April 2014.

That coincidentally is also about the time when two of the existing 4-car trains will be sent up to Derby to be fitted with the 5th carriage for testing purposes. The two trains also need to be fitted with dual-voltage systems first so that they can get up to the Derby testing centre. Does mean that the two trains will be dual-voltage for future use as well, should such a need arise.

The loss of the two trains should affect the service, but a deal with Bombardier saw the number of trains needed as a buffer for maintenance work reduced so that passenger wont notice the two trains are elsewhere.

While that is going on, platforms at a number of stations will start to get lengthened in the first significantly visible sign that the upgrade is one its way.

Some platforms simply cannot be extended, such as Rotherhithe or Wapping, where selective door opening will see the 10 doors on the train reduce to 8. Surrey Quays was thought to be an eight-door station, but there is a bit of dead space at the southern end to extend the platform enough to add a bit more, so it will see 9 doors out of the 10 opening.


Towards the end of next year, we should start to see the first passenger trains enter service with their new 5th carriage bolted on. Once that starts, they expect to convert a train per week, so about a year to roll out the entire fleet.

Ordinarily, having trains of either 4 or 5 carriages arriving means that the end carriage is little used as people wont wait on the platform where an occasional carriage might arrive — but as these are walk through trains, people can wait on the platforms at the 4th carriage stopping point, and then walk through to the fifth is it is there.

So we users should feel the effects of the longer trains much sooner than might otherwise be the case.

The longer trains will initially arrive on the East London Line section, with longer trains arriving on the Richmond/Clapham Junction to Stratford Line towards the end of 2015.


Slightly off topic, but the machines for damping down gravel — never seen three of them hooked up together like that. It looked quite impressive, and nicely controlled by a remote radio link which is a good way of preventing white finger.


Site access to Silwood was courtesy TfL and London Overground.







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  1. dave_in_chiswick says:

    Very interesting stuff. I may be getting (way) ahead of myself, but do you see a possibility of extending the depot sites to 6-car length in future? Sounds like things are tight enough already if it’s reducing siding capacity.

    Item 3.8 of the a TfL report on the programme states:
    “As part of LOCIP, where reasonably practical, provision is being made to accommodate six car trains.”

    I also expect selective door opening would be quite an issue on the shorter platforms. Judging from my daily commute the added capacity provided by a 5th car would be swallowed up very quickly however, so I do see 6-car as inevitable (and the likely maximum limit).

  2. Sykobee says:

    The problem of six cars on these lines that have short 4-car platforms is that entire cars end up without an opening door on them. At least the 5-car trains mean that people in the wrong place don’t have far to go, even on a walk-through service.

    However, it may be inevitable because of footfall – at least it is walk through. Of course, everyone will get fed up of the announcements before each station! “Passengers for Wapping please be aware that doors will not open in the front or rear carriage, please leave the train from the middle four carriages”. However I believe another issue is that the current four car units really aren’t suitable for extension to six cars, and the five cars is pushing their capability.

    Considering how recently the New Cross Gate depot was built, I am surprised it didn’t have passive provision for five-cars – losing so much capacity as a result is quite shocking.

    And in 2040 when the overground is 24 hours and trains are never stabled, there’s going to be some nice prime location land for TFL to sell off.

  3. Chris says:

    While 6-car trains with the front and rear carriages locked out may be possible, this would have a severe impact on dwell times while people got on and off especially at Canada Water and I doubt such trains could fit in the reversing sidings at Dalston Jct.

    Automatic train operation would seem a more likely way to increase capacity in the future.

    …and sorry Sykobee but there’s no way the tube could run 24/7 365 days a year, even in 2040!

  4. Paul says:

    A majority of the LO fleet are already dual voltage. Although the first batch specifically intended for the ELL was DC only, all the subsequent extra trains for the extensions were capable of running throughout the LO network as delivered, so I don’t think anything specific should need to be done to send two trains to Derby, assuming they choose the right pair.

    None of the dual voltage units are actually dedicated to one route or another, so if two trains are going north they won’t necessarily both impact on the ELL, one might go from Willesden.

    I don’t think the dual voltage variants are neatly pigeonholed into ELL and the rest anyway, they change around now and again.

  5. Dave says:

    FYI: Silwood sidings is being preped for 6 car.
    Why they didn’t future proof the depot and line is mind boggling. How much is the LOCIP extension costing the tax payer? Silwood siding, depot rearrangement, shed extensions, platform extensions, signal reconfig. Doesn’t take a genius to see halve the cost could have been saved from the starting pistol of ELL phase 1.
    Also, for a journalist, the grammar in your article is shocking. PROOF READ DUDE!

  6. Jason says:

    I pointed out in 2003 when we were informed that 4 carriage trains were planned, that they should be planning for 6 or 8 car trains. I do the Kensington Olympia journey to Clapham Junction. At peak evening times there are always people left standing on the platform as they cannot fit onto the trains. I could understand if this was due to breakdowns or signal failures but to happen regularly is a disgrace.
    If the trains were not so over crowded, journeys would be more pleasant and more people would use the service (which is what TFL would like). With one extra train you will over capacity in no time. If you are investing in upgrading the system, then take the opportunity to make a significant impact.

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