Stirling Prize shortlist 2024: The Elizabeth line – line-wide design, London, by Grimshaw, Maynard, Atkins, Equation

Running across London, from Heathrow Airport and Reading in the west to Shenfield and Abbey Wood in the east, the Elizabeth line comprises 62 miles of track, 26 miles of new tunnels and 10 new and 31 upgraded stations, and now averages 700,000 passenger journeys every weekday. Grimshaw, with Maynard, Atkins and Equation, was responsible for the line-wide design, with a further nine practices responsible for the new stations. Neill McClements, partner at Grimshaw and lead architect on this project, explains the processes that led to this intuitive, safe, accessible and enjoyable travel environment.

What strikes you as key to the design process?

Neill McClements For me, it’s collaboration. It was an unusual to have so many architects working so closely together, from the client architecture team led by Julian Robinson, to the nine practices involved with the new stations, all of whom had full engineering and design teams. Then the separate contractors for each station had their own design teams too. It was an amazing experience to be right in the midst of everything, interfacing with so many different parties, all the way from concept design in 2009, to final delivery.

How did you go about that collaboration?

The client had taken two floors in Canary Wharf, and we were all appointed at pretty much the same time, so we spent two years or so co-located, building togetherness and running workshops. That was essential for a project of this scale – we were developing a brand new typology for London, with high-frequency trains running on heavy rail beneath the city, arriving on 240m-long platforms, each with east and west ticket halls, with a scale of tunnel environments that was a fundamental change from what had gone on before.

Was there a tension between the individuality of the stations and the line-wide elements?

The brief for the station teams was to ensure each integrated sensitively with the historic fabric, but the client also wanted a consistent look and feel across the line – one that also spoke to London – so that was our brief. We all had to think about what that meant in reality – who is designing which bits, which are common, which are station-specific, how to achieve a transition. Early on, we jointly developed a strategy whereby the closer you get to the train, the more consistent the experience, on a sliding scale from street level to platforms. There were common aspects, like expression of soffits and structure, or the celebration of the junction between ticket hall and escalator, as well as a shared family of products, but achieving that clarity around ownership was vital to the project’s success, freeing us up to think about the overall strategy for the line-wide identity.

How did you arrive at your architectural approach?

The use of sprayed concrete tunnel lining, as well as being safe and efficient, was a big influence, allowing the tunnel forms, from the platforms through to the connecting tunnels, exits and escalators, to be seamless.. We developed curvaceous junctions, opening up sight lines and improving passenger flows, with a continuous grid of lines flowing from one space to the next. That concept was arrived at quite early, but the realisation was a long journey. One of our key roles was to bring standardisation across the project – there was no valid reason to make things different for the sake of being different, but significant benefits to one intelligent solution. We were constantly seeking to simplify geometries, when developing the double-curvature panels for instance, minimising the number of moulds to reduce costs. Once you’ve gone through all that, you have more time to spend designing fewer elements, helping to de-risk later stages of the process.

What were your priorities in the subterranean areas?

Right from the start, we wanted to celebrate the engineering of the spaces, expressing the full volume to passengers. But we also needed to humanise them – when you’re 30m below ground it needs to be uplifting, not claustrophobic. To ensure they were pleasant environments for way-finding, we developed a strategy with Equation, the lighting engineers using indirect lighting with warm colour temperatures on the larger platforms and concourses. In the smaller cross-passages that link these, we employed direct light and cooler colour temperatures.

Another goal was to reduce station clutter and visual noise, which proved a strong generator for the platform architecture. We dedicated the ‘arrivals wall’ – in front of you when stepping off trains – to TfL signage and street maps, to create a calm, neutral environment for passengers deciding which ticket hall to head to – if you get that wrong, you’ve got a long walk at street level. Glare was minimised by placing lighting above the platform screen which created a full-height ‘departing wall’ containing information systems, cameras, communication equipment, cabling, but also digital advertising, removing it from the arrivals wall. Grouping technology in this way was a complex process, sometimes with competing technical requirements, but it allowed a modular approach with hinged access to service elements that have shorter lifespans, removing it from tunnel linings. We went through a similar process with the service totems, making them hard-working engineering elements, integrating everything from lighting and cameras to control barriers and signage.

How did you test these strategies?

One of the first things we realised was the need to communicate these ideas to many teams, so we created a full-height set-design of a platform and cross- passage in a warehouse in Leighton Buzzard, conveying their spatial and performance characteristics. That set us off on a journey that soon progressed to real materials, allowing us to start working with suppliers. Helped by economies of scale, we could prototype almost all the elements, creating full-size panels to think about detailing and fixing systems, introduce hinged access, incorporate signage and so on, but also to work on weight reduction, durability and sustainability – the carbon payback period should only be 10 to 12 years. We could then show them to contractors, so they had a full understanding of what they were being asked to do, and could then build their own prototypes, allowing a further process of refinement. It also facilitated feedback from other parties, such as maintenance staff raising concerns about operation – a single borescope inspection hole was added to acoustic panels for instance – and standard tests around spillages and so on. It gave everyone confidence that ideas would work: information could be shared early and we could all hit the ground running.

But there was also a digital story. Unlike other teams, we didn’t actually have a station, so we created full designs for an imaginary one, collaborating with station teams to share common spatial elements via BIM and CAD technology. Then we could constantly update drawings and specifications, issuing them to station teams to integrate in their own models, for example when we’d established the minimum and maximum spacing around totems. It was a key communication device, helping to ensure the design was developed with sufficient rigour.

Looking back, what gives you particular pleasure?

Really it was the entire process – working with so many different design and construction teams and the combined expertise of the architectural practices working across the whole line. An infrastructure project of this complexity takes years to deliver, with a commitment and collaboration across a large part of many people’s careers. But witnessing the reaction of Londoners to the line’s opening, and even today two years later seeing the impact it has on the city, brings a sense of pride for everyone involved in the project.

See all six projects shortlisted for the 2024 RIBA Stirling Prize

Key data
Contract value £18,600m

The 2024 Stirling Prize is sponsored by Autodesk