HS2 HS2Construction M42 ModularConstruction DfMA

HS2 prepares major beam installation for M42 twin box structure

Jun, 17, 2026
Bridges Bridge Design Bridge Management General Construction News On Projects / Industry
United Kingdom
Authored by: TheCivilEngineer.org

*HS2’s twin box structure over the M42 near Solihull, where prefabricated roof beams will be installed during weekend motorway closures. Source: HS2*

HS2 engineers are preparing to install roof beams for a new 300 m long twin box structure over the M42 near Solihull. Once complete, motorway traffic will pass through the twin box while HS2 trains run above, carrying four railway tracks across the motorway.

The structure sits on the HS2 mainline, less than a mile from the future Interchange Station in Solihull. It is positioned between the Packington embankment and the Pool Wood embankment, forming a key part of the route through the West Midlands motorway network.

The next construction phase will require four weekend carriageway closures between June and September 2026. The first closure will affect the M42 from 9pm on Friday 26 June to 5am on Monday 29 June, allowing engineers to begin placing the prefabricated beams safely above the carriageway.

The twin box has been developed using a modular construction approach known as Design for Manufacture and Assembly. This method has allowed major elements of the structure to be manufactured off site and installed more quickly on site, reducing the need for lengthy motorway closures.

The supporting walls, now structurally complete, are approximately 10 m high and were built using prefabricated hollow blocks. Each block weighs an average of around 14 tonnes and was lifted into position before being stitched together with reinforced concrete. A central pier of 46 supporting columns is also nearing completion within the motorway central reservation.

The next stage involves installing 175 prefabricated beams, each 23 m long and weighing between 56 and 92 tonnes. These beams will form the roof of the box structure and will support a total beamed roof weight of around 9,800 tonnes. A 300-tonne crawler crane will lift the beams into place, bridging the gap between the external walls and the central columns.

The beam installation is a complex operation because it must take place over an active motorway. Engineers have planned the works across four weekend closures, with around 44 beams expected to be installed during each closure. A team of approximately 180 engineers and specialists from Balfour Beatty VINCI and Expanded will work in shifts around the clock to complete each phase and reopen the motorway on schedule.

The construction strategy reflects the challenge of delivering major rail infrastructure within constrained public corridors. According to HS2, the use of prefabricated components and modular assembly has reduced the need for lengthy motorway closures and moved more work away from the live motorway environment.

The M42 twin box is one of three major HS2 structures being delivered across the Midlands motorway network this year, alongside the Water Orton twin viaducts and the M6 South viaduct. Its construction shows how off-site manufacture, heavy lifting and carefully staged closures are being combined to deliver large infrastructure works while managing disruption to road users.

For road users, the temporary closures will require journey planning and use of approved diversion routes. For the project team, the works represent a significant stage in delivering the HS2 route through the West Midlands motorway network.

Sources: mediacentre.hs2.org.uk, kenilworth.nub.news