TfL and Motts discuss West London Orbital Overground line as feasibility stage completed

The WLO would fill a missing link in the network between north and west London. The 18km route would cross four London boroughs, stretching from Hounslow in the south west to Hendon and West Hampstead in the north.

It has been mooted as one of TfL’s priority network extensions, alongside the Docklands Light Railway (DLR) extension to Thamesmead and the Bakerloo line extension, for some years. But, like those other projects, it was impacted by the Covid-19 pandemic, which saw TfL take a financial hit that saw its long-term capital projects indefinitely delayed.

While TfL is still recovering from the impacts of the pandemic, it is gradually starting to breathe life into these long-term projects. A business case is being put together for the DLR extension and feasibility studies are being drawn up for new stations on the Bakerloo line.

An inkling that the WLO was progressing was given in April 2023, when Mott MacDonald was appointed to carry out feasibility design.

That stage is now complete, but “it is not by any means a committed scheme at this stage; the funding is not all in place”, according to TfL major projects and urban design manager Matthew Rheinberg.

However, it has a strong case, it is in the mayor’s transport strategy and in the local plans of all the boroughs it crosses, which are represented by the WLA in the project.

TfL is currently “looking to get all the bits of the jigsaw together to move it forward into the next design stage”, Rheinberg said. It is hoped that this will take place in the next year, allowing a single option to be selected and for the project to move for a Transport and Works Act Order to enable delivery of the scheme.

The case for the West London Orbital

The route of the WLO would cover the western side of London, “filling a big gap in the orbital public transport capacity”, according to Rheinberg.

“You’ve got this section of west and north west London where there are some orbital roads, like the North Circular, but to get anywhere by public transport you need several buses on a congested road network – it’s slow going,” he added.

It would directly serve five Opportunity Areas, described in the mayor’s London Plan as having “the potential to deliver a substantial amount of the new homes and jobs that London needs”.

“Orbital connectivity is one of the biggest challenges that outer London boroughs face and this route goes a long way to providing an orbital route,” WLA net zero, infrastructure and transport lead Anthony McNamara said.

Additionally, WLO will help relieve capacity on the public transport network by presenting new connection opportunities, Rheinberg explained.

“It crosses various lines like the Jubilee line, Elizabeth line, Bakerloo line and other London Overground routes,” he said. “While post-Covid some of these routes aren’t as busy as they were at peak hours, they are still forecast to be very congested in the future.”

It will also benefit High Speed 2 (HS2) as the new Old Oak Common Lane station will be connected to the Old Oak Common superhub station. Rheinberg said that even once HS2 is running to Euston, it would still be quicker for people in this “quarter” of London and out into Hertfordshire and Surrey to get to and from HS2 services via the WLO to Old Oak Common.

Rheinberg also touched on the social and environmental benefits that the WLO would have by encouraging modal shift from cars to public transport, which would reduce congestion and pollution, therefore improving air quality.

Infrastructure complexities

The WLO would run entirely on existing track, such as the Dudding Hill line between Acton and Cricklewood, but there are still various upgrades needed across the route to make it viable for use by the London Overground. While this has the benefit of not needing to construct masses of new lines, it does present the challenge of working on operational railways.

“As quite a major piece of infrastructure work, there are a lot of key challenges,” according to Mott MacDonald associate structural engineer Chris Williams, who worked as project and design manager on the feasibility stage of WLO.

“You’ve got a combination of existing operational lines at the southern side, you’ve got freight lines which will need to be upgraded in terms of signalling, there’s some twin tracking pieces of work and stabling – that presents a number of challenges that need to be overcome.”

Williams further mentioned the “logistical challenges and constructability issues with some of the larger sites”, specifically brand new stations and interfaces with existing stations.

“The other things we’ve been looking at are operational logistics such as making sure there’s sufficient turn backing, stabling, operational resilience and practicalities of access for new rolling stock that would need to be provided,” he said.

Williams added that with the train frequency that has been stipulated will require numerous level crossings on the line to be removed – but this would sever key routes for pedestrians and cyclists. “We’ve developed a number of step-free access routes or provisions for the public to be able to overcomes the severance issues that would create,” he said. “Some of them are major technical challenges that we’ve been working through to conclude the feasibility stage.”

One of the bottlenecks that will present the biggest challenge to the project is Acton Wells junction. This is a key route for freight services using the Dudding Hill line and at this point it crosses existing London Overground services near Acton Central and on the North London line (soon to be renamed the Mildmay line).

“There would need to be some major new track works and resignalling works to enable the train frequencies and allow freight to still facilitate around – that in itself is quite a substantial piece of work,” Williams said.

Twin tracks at Acton Wells will have to be doubled to allow passing routes and “in doing that there’s a large number of new bridges that would be needed to improve capacity over some sections because it’s currently not doable”, according to Williams.

“Within the existing corridor there’s also a substantial amount of existing signalling asset and building there, which would need to be redone elsewhere,” he continued. “From a constructability point of view, it would be lots of piecemeal minor movements to keep the line open while the works are going on; it’s so critical to the area that you wouldn’t be able to shut it down for six months without crippling freight and passenger services in the area.”

“At the most we’ll be able to get weekend possessions [at Acton Wells],” Rheinberg said. “You could do it much quicker and easier if you could have much longer blockades, but it’s not realistic.”

The engineers would use these possessions to carry out works at other locations on the route to mitigate disruption as much as possible.

New stations

The WLO will see the establishment of four new TfL stations: Lionel Road, Old Oak Common Lane, Harlesden and Neasden. Additionally, a new platform will be added to the recently-opened Brent Cross West station to enable services to stop there.

Each of these has a strategic benefit to London, with most offering new connections on TfL’s network.

Lionel Road will be a new stop for Brentford FC’s stadium and serves the Great Western Corridor Opportunity Area. Old Oak Common Lane serves the growth area of Old Oak Common and will have a connection to the under construction HS2 superhub station, therefore providing interchanges with the Elizabeth line and HS2 services. Harlesden and Neasden will have Bakerloo and Jubilee line interchanges respectively.

Brent Cross West will allow interchange to Network Rail’s network as it is on the Midland Main Line.

The size of the new stations varies depending on the constraints, but all will allow for new five-car trains, meaning 130m long platforms.

“At Lionel Road we have the football stadium right up to the edge of the tracks on one side and an office building that is proposed for a fairly major mixed use development right up to the tracks on the other side, so we’re really constrained there,” Rheinberg said.

“We’re squeezing it into the existing rail corridor, so a very tight spot,” Williams added.

“Some of the other locations have less constraints but they all have some degree [of challenge], whether it’s existing housing or industrial buildings or road bridges,” Rheinberg said.

When it comes to Old Oak Common Lane, there are a “number of options on the table” according to Williams. “That’s more being driven by how best to integrate it with the connectivity between that and passive provision for a North London line station nearby, as well as making it tie in with the HS2 station and the surrounding area masterplan,” he added. “So there’s a bit more ambition with that station, I would say.”

Harlesden station will be “very limited” according to Williams. “It’s across the road from the existing station up on the embankment,” he said. “That site is very constrained and you can just about fit the station up on the embankment. It’s about achieving the most practical way of enabling step-free access from the street up onto the new platforms and minimising travel distance for local residents.”

At Brent Cross West, passive provision was made for the new platform in the station development to allow it to be “bolted on”, according to Williams. “That itself has challenges in itself of additional track movements and trying to minimise disruption,” he said.

Going forward

Rheinberg said that the anticipated cost of delivering the WLO scheme is “in the £800-900M type range” in current prices. The funds would come almost entirely from TfL and the WLA.

“It’s not really a scheme where we could get a public-private partnership type solution because it’s all Network Rail’s infrastructure,” Rheinberg said.

McNamara said there might be potential for private finance but “it would be small in the grand scheme of things”.

“I think the challenge very much at the moment is the state of local authority finances and trying to raise money for investment in schemes like this,” McNamara continued.

“TfL is in a similar position where it has some funding but it can’t afford to pay for the next stage without some assistance. We’re hoping that over the next weeks or months we will be able to come up with the solutions we need to begin the next stage.”

TfL is hoping that a public consultation on its plans for WLO is in the offing for 2025. The application for a Transport and Works Act Order would be submitted around the end of 2027 or start of 2028.

“Assuming we successfully get through the consent, we’re then looking at construction starting around 2030 and services starting in 2033,” Rheinberg said.

Like what you've read? To receive New Civil Engineer's daily and weekly newsletters click here.