HS2 Prepares Major M42 Installation as ‘Giant Lego’ Structure Takes Shape

HS2 engineers are preparing to begin one of the most significant construction phases on the high-speed rail project this summer, with the installation of hundreds of massive roof beams over the M42 near Solihull.

The work will create a 300-metre-long twin-box structure that will eventually carry four HS2 railway tracks above one of the Midlands’ busiest motorways, while traffic continues to pass through tunnels beneath.

The project marks a major milestone for the railway and showcases an innovative modular construction approach that has been compared to assembling giant Lego blocks.

Modular Design Reduces Motorway Disruption

Construction teams have already completed two substantial supporting walls on either side of the motorway, while a central pier comprising 46 support columns is nearing completion within the central reservation.

The 10-metre-high walls were built using large prefabricated hollow concrete units, each weighing around 14 tonnes. Once positioned, the blocks were joined together using reinforced concrete to create the structural strength required to support the enormous roof structure above.

This Design for Manufacture and Assembly (DfMA) approach has enabled engineers to carry out much of the construction work off-site, significantly reducing the need for prolonged motorway closures.

Attention is now turning to the installation of the roof beams that will complete the structure.

Four-Weekend Installation Programme

A specialist workforce of around 180 engineers and construction professionals from Balfour Beatty VINCI (BBV) and Expanded will oversee the operation.

Working around the clock in shifts, teams will install a total of 175 precast beams over four separate weekends throughout June, July, August and September.

Each beam measures approximately 23 metres in length and weighs between 56 and 92 tonnes.

A 300-tonne crawler crane will lift the beams into position, spanning the distance between the supporting walls and central columns to form the roof of the structure.

Given the scale of the operation, temporary motorway closures will be required during each installation phase. Around 44 beams are expected to be installed during each weekend closure.

The first stage of works is scheduled to conclude before the motorway reopens at 5am on 29 June.

Key Structure on HS2 Route

The twin-box structure forms a crucial section of the HS2 mainline and is located less than a mile from the future Interchange Station in Solihull.

Positioned between the Packington and Pool Wood embankments, it will eventually carry four railway tracks across the motorway corridor.

The project is one of three major HS2 structures being delivered over the Midlands motorway network this year, alongside the Water Orton twin viaducts and the M6 South viaduct.

‘British Engineering at its Best’

HS2 Senior Project Manager Agnes Usciak described the installation as a significant moment for the programme.

“This is a huge moment for the project, and a clear sign of the progress we are making as we begin bridging the gaps over the region’s motorway network.”

She also praised the innovation behind the design and manufacturing process.

“This is British engineering at its very best, and it’s fantastic that a UK-based firm has led the way in developing this innovative design solution for the twin box, with manufacturing taking place in the Midlands.”

Collaboration Key to Delivery

The project has been developed in partnership with National Highways to minimise disruption for motorists while maintaining construction progress.

Balfour Beatty VINCI Project Director Oliver Shore highlighted the scale of the engineering challenge.

“This ambitious structure, spanning a busy stretch of the M42 motorway near Solihull, is a huge engineering challenge which has required precision planning and close collaboration with many stakeholders.”

He added:

“Now the supporting walls are complete, we’re getting ready to move to the next exciting phase of construction, which is the installation of the roof over four weekend carriageway closures throughout the summer.”

Innovative Construction Approach

The design and delivery of the structure is being led by Expanded Structures, a UK specialist in modular bridge construction.

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The precast components have been manufactured by Nottinghamshire-based Explore Manufacturing at its Worksop facility, which employs more than 400 people.

Expanded previously delivered the first permanent structure on the HS2 route in 2020, installing a modular bridge across the M42. More recently, the company has played a major role in the construction of Old Oak Common station.

Expanded Project Leader Tim Rowe said minimising disruption for road users had been a central design principle from the outset.

“Throughout the planning for this project it was an underlining principle that there would be minimal disruption to road users.”

He added:

“Our modular bridge solution offers a quicker and safer installation to that of traditional bridge construction, leveraging the benefits of off-site manufacture to take risk and disruption away from the site and public interfaces.”

Looking ahead to the beam installation programme, Rowe said:

“Whilst the bridge is already an impressive structure we have been looking forward to this moment, installing the beams and connecting all the individual elements in one continuous structure.”

Focus on Motorist Impact

National Highways has worked alongside HS2 and its contractors throughout the planning process, helping to coordinate road closures, diversion routes and community engagement activities.

National Highways Head of Network Planning and Development Ian Doust said:

“Throughout the process our focus has been on minimising disruption for those who use our roads and we have worked closely with HS2 and their partners to that end.”

He added:

“We welcome the innovative measures being taken which will substantially reduce the impact of this huge infrastructure project on our road users.”

With beam installation set to continue throughout the summer, the project represents another visible step forward for HS2 as construction progresses across the Midlands and key sections of the future railway begin to take shape.