Not far from Paddington can be found a small, but surprisingly important part of the Crossrail project.

The Acton Yard [map] is a major logistics hub for London, and one of the busiest rail goods depots in London, handling mainly heavy aggregates for the construction industry. Trains flow in and out of here throughout the day, and they pose a potential threat to Crossrail.

The depot sits to the north of the mainline tracks in/out of Paddington, and while trains heading into London simply slip sideways into the Yard, those that leave have to cross the London bound tracks to get to the southern side of the railway so that they can head out of London.

Anyone who has seen freight trains on the London Overground (and elsewhere) will appreciate just how staggeringly long they are — and having really long trains crossing the London bound tracks can block the tracks for several minutes.

Currently, not really a problem as they are timetabled to slot in between passenger trains, but along comes Crossrail, and those gaps in the timetable vanish.

To stop London-bound Elizabeth line trains from being delayed, there needs to be a way of getting the cargo trains across the tracks, without blocking the traffic. A bridge over the tracks was ruled out, so as is often the case with Crossrail, they went underground instead.

A 730-metre long dive-under has been constructed at Acton letting London bound trains pass underneath the freight trains when necessary.

It’s a long thin stretch of railway cutting that has been exceptionally difficult and time-consuming to build.

Firstly, there wasn’t any space for it, so the entire freight depot had to be shunted slightly further north. Fortunately, the depot is closed on Sundays, making work slightly easier, and the freight depot took the opportunity to redesign its layout a bit.

Work on that started back in 2011.

A slither of land sliced out between the passenger railway and the depot, and for the past couple of years, Bam Nuttall has been digging down to construct the dive under.

It’s both quite basic, and yet very complex.

It is in essence, a couple of parallel lines of piled driven into the ground to form two walls, some 5.6 meters apart, then the soil was dug out between them to create the dive under.

In the middle sits both the reinforcing to stop the sides collapsing and the tracks leading from the freight depot that are the entire point of the dive under.


Unfortunately, construction had to be done on a site that had fast running passenger trains just feet away on one side, and heavy trundling freight wagons on the other.  A mishap with the construction could have seen a landslide that would have taken out the mainline railway into Paddington for months.


If that wasn’t enough to contend with, they had just one access point to the site, meaning that construction materials arriving used the same access as the waste leaving. They estimate construction time could have been halved had a second entrance been possible.

At the moment, they are building the remainder of the sidewalls on the eastern side of the box, and laying the last of the floor slabs which will carry tracks to junctions allowing trains to slip back onto the mainline.


Over Christmas, the mainline out of Paddington will be closed for a few days, so that sites such as this one, or at Stockley can get to work on creating junctions or ripping up tracks they can’t otherwise get at.

The work on the dive-under is being managed by Network Rail and is expected to last until 2016.


As with all major infrastructure projects, Crossrail has brought forward things that were wanted but maybe not likely to happen in the short term. Such as a dive under at Acton so that mainline trains heading into Paddington aren’t delayed by empty wagons heading west to pick up more building materials for London’s insatiable construction boom.

When it is all finished, that small but complex bit of work, a single line of track in a cutting will do more to cut delays on the mainline into Paddington that could ever be appreciated by its simple size and design.








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Article last updated: 6 December 2021 09:14


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  1. Paul Harley says:

    Wouldn’t it have been easier to build a dive-under to send the freight trains under the Up Relief? They would depart the yard at slow speed, so it would have been acceptable to have tight curves to/from the dive-under.

    • Ian Visits says:

      I’m sure wiser heads would have looked at all the options before deciding on what they would build — but on this one, I suspect the main downside being the sheer difficulty of digging under a live passenger railway line.

    • Jamie says:

      The other issue with a freight diveunder would be that very heavy trains aren’t that easy to drive on large gradients, whereas express services can use momentum to run through.

    • Allan P says:

      Have you studied the site? Heavy freight trains would obviously have more trouble ascending a ramp from a standing start than (mostly) DMU’s travelling at speed. Secondly, to provide room for the dive-under cutting on the country side, one or both relief lines would have had to be slewed over, involving much more work and probable interruption to services. Excavations and fitting-out would also have had to proceed between much busier tracks.

  2. John B says:

    Those pop-up windows inviting me to subscribe to your email newsletter are really starting to irritate, especially since I’ve already done it. You need to be less intrusive advertising the service, which is really useful.

    • Ian Visits says:

      If you click the X, it should set a cookie that lasts a year to not show it again. Do you have a plug-in that blocks parts of websites from working?

    • Robin Green says:

      What annoyed me with your popups is even after I’d actually subscribed to your newsletter, the popups kept on appearing! And no, I don’t have anything that would block parts of the page from working.

    • John B,
      Ian went all the way down there to take the pictures, research the piece and took the time to write the article. The least time would have been half a day. He then puts this up for free and your entertainment and all you can say is a moan about the pop up window?
      That very poor form. Without advertising most websites would not be able to survive so stop moaning about it. Half a days work and you complain about having to move your mouse an inch and click a button. Its hardly fair.

    • Julian B says:

      Echo Grateful Reader’s comments: excellent article by Ian.
      JohnB: be good, show a bit of gratitude.

  3. PETER BISHOP says:

    Peter B,

    Ian, many thanks for your thoughtful piece on the Acton Diveunder. It is indeed a complex piece of civil engineering, which will eliminate a potential pinch point on the Crossrail project. With your permission we would like to link your article to the BAM Nuttall website and send out further links via social media.

  4. Marcus Gibson says:

    Another excellent transport piece, Ian. As a former FT tech correspondent may I make a 30 second moan about Crossrail, the fact it was built at all?
    What London needed is a multi-tier, multi-mode west-east surface link from the M40/Paddington to the east of London, with four rail tracks, two tiers of road and a cycling/footpath on top. It could have been built along the Euston/Marylebone Road pathways easily and quickly – and for one quarter the cost of Crossrail – which is the highest cost, lowest capacity, longest-by-far-to-build option.
    Worst of all, Crossrail will be like the Jubilee Line – if one nut falls off one train the entire line is halted as the trains are packed together. Given the Uk’s reputation for dire signalling quality – this may be common. Similarly, having only two tracks means no through trains.
    Overall, Crossrail was the very worst option – beloved and promoted by Ken Livingstone, the master of all that fails, of course.

  5. Julian B says:

    That’d be the same Ken who turned the North London Line into London Overground, replacing an infrequent, unreliable and generally scary service into a high frequency, well patronised, safe and bright service it is today,

    I can’t quite believe that anyone would want a 4 track railway and road etc going through the the heart of London. Apart from looking absurd, the pollution it’d generate would make the UK”s current worst highway, which coincidentally is Euston/Marylebone Road, a comparative breath of fresh air. Crossrail will be a huge success, even if there are occasional lapses as you forecast.

  6. Petras409 says:

    And with London still breaching Clean Air directives, one thing it doesn’t need is a new road.

    Crossrail will actually help with clean air, being electric and pollution free plus, with luck, will help to cut road traffic that currently doesn’t have a better alternative for longer distance journeys across London.

  7. Dr Strabismus says:

    Marcus Gibson, complete tosh on every level – cost, practicality, intrusion, pollution and ineffectuality. To propose massive road capacity thereby attracting thousands more vehicles into central London through the M25 effect is insane and highly irresponsible. An elevated artery along that corridor might reach King’s Cross – then what? Demolish huge swathes of Islington, Clerkenwell? Maybe 150 years ago, but not today. Londoners summarily rejected motorway box proposals decades ago, and London has thrived ever since. Build a 4-track railway underground, at double the cost of Crossrail? Yeah, right.

    Crossrail is itself a high-speed limited-stop railway parallel to both the Central and Metropolitan lines, so there you have your multi-tier service; the differential performance and resilience are built into the whole network, not just individual lines. The same logic applies to Crossrail-2; none of these are conceived and built in isolation, but to supplement and bolster the existing network.

    Ian, another excellent article, thank you very much.

  8. MikeP says:

    And, to add to my tupp’orth to the criticism of Marcus’ proposal – what is your basis for your assertion that this would come in “at a quarter of the cost of Crossrail”. I’d like to see some evidence other than handwaving. And this comparison should be based on total project, disruption (remarkably little for Crossrail) and connectivity costs

    My handwaving, on the other hand, suggests that the overall cost would have been much more, and the objections myriad. Given that Crossrail only just got under the wire financially (with significant “value engineering”, such as stopping at Abbey Wood), I don’t think such a scheme would have seen the light of day. Better something (arguably) worse that we can have, rather than something better that we can’t.

  9. Robin says:

    I went past it yesterday on a journey from Ealing to Paddington. As it is now fully open I was surprised that not all traffic uses it on the relief line. All that engineering and it is only an occasional option, I thought it would replace the existing stretch of the relief line?

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