HS2 engineers are preparing to begin the next major phase of construction on a 300-metre-long twin box structure that will carry the high-speed railway over the M42 near Solihull.
The structure, located less than a mile from the future HS2 Interchange Station, will eventually allow vehicles to pass through the box while trains travel above on four tracks.
The next stage will see 175 prefabricated roof beams installed across the motorway over four weekend closures between June and September.
Each beam is 23 metres long and weighs between 56 and 92 tonnes. They will be lifted into place using a 300-tonne crawler crane, bridging the gap between two completed supporting walls and a central pier being built within the motorway’s central reservation.
The walls of the twin box have already been constructed using prefabricated hollow blocks, compared to giant Lego bricks. Each block weighs around 14 tonnes and has been stitched together with reinforced concrete to support the 9,800-tonne roof structure.
HS2 said the use of modular construction methods, known as Design for Manufacture and Assembly, has significantly reduced the need for prolonged motorway closures.
The first closure will take place from 9pm on Friday 26 June until 5am on Monday 29 June 2026. It will affect the M42 between Junctions 5A and 7 northbound, and Junctions 6 and 7 southbound.
The twin box is one of three major HS2 structures being built over the Midlands motorway network this year, alongside the Water Orton viaducts and the M6 South viaduct.
Agnes Usciak, HS2 Ltd’s Senior Project Manager, said: “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.
“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.”
The design and installation approach has been led by Expanded Structures, with precast components manufactured by Explore Manufacturing at its Worksop facility in Nottinghamshire.
Balfour Beatty VINCI, HS2’s construction partner in the West Midlands, will deliver the installation with Expanded. Around 180 engineers and specialists will work in shifts around the clock during each weekend closure.
Oliver Shore, Project Director at Balfour Beatty VINCI, said the structure presented a major engineering challenge on one of the region’s busiest routes.
“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 said.
National Highways has worked with HS2 and its contractors to plan the closures and diversion routes. Drivers are being urged to allow extra time and follow signed diversions during the works.
Ian Doust, National Highways’ Head of Network Planning and Development, said the organisation had worked closely with HS2 to reduce disruption.
“We appreciate that there will still be some disruption during these weekend closures so we would advise people to leave extra time for journeys and choose alternative routes if at all possible,” he said.
The roof beam installation is scheduled to be completed in September.
