The incredible new ‘twin box’ that will transform major UK motorway

A major point has been reached in the construction of HS2 as work on a 300-metre bridge is due to begin.

HS2 engineers completed essential preparation work on a section of the M42, finishing the work five hours earlier than planned.

Building work will now begin on the 300m bridge structure that will carry the high-speed railway over the major UK motorway.

The construction method will use hollow building blocks to create a ‘twin box’ structure which will cut construction time and reduce disruption to road users.

During two weekend closures, the team of engineers prepared the area for construction by removing pre-existing concrete foundations, installing underground ducting and creating a safe working area in the central reservation of the motorway. 

Once built, the M42 motorway box structure will measure 300 metres in length and will enable the high-speed line to cross over a 130-metre stretch of the M42 between junctions six and seven near the NEC in Birmingham.

The structure will be built using a modular construction method which reduces the need for lengthy motorway closures, minimising disruption to road users. 

It involves the assembly of giant building blocks that are manufactured away from site and transported to land next to the motorway.

The structure is due for completion in early 2027. Working in collaboration with National Highways, HS2 will build the structure in position while keeping three lanes of carriageway open on the M42, with a 50mph speed limit in place.

Doug Barnett, senior project manager for HS2 Ltd, said: “I commend our site team who worked through the night to complete this essential work, enabling the motorway to reopen five hours earlier than planned.

“Following this first phase of work, we can now start to build the structure in place from the ground up. 

“We’ve prioritised a modular, self-supporting construction method as this avoids the need for any long-term motorway closures and reduces the overall construction time frame – keeping disruption to a minimum.”

HS2 and its main works civil contractor for the West Midlands, Balfour Beatty VINCI (BBV), will continue to work in partnership with National Highways as the build gets underway. 

At peak construction, a dedicated workforce of 150 will support the complex operation, bringing jobs to the area, too.

Oliver Shore, project director at Balfour Beatty VINCI, said: “Now we’ve completed essential preparation works along a section of the M42, we’re ready to begin building this twin box structure which will carry HS2 trains over the motorway. 

“Using a modular construction method, this impressive structure will be built in position, to minimise disruption on road users.”

David Patmore, Network Planner for National Highways, added: “It is crucial for us that we keep traffic moving and we do all we can to ensure people’s journeys on our roads are as smooth as possible. 

“When we need to carry out important and significant works such as these, we work closely with partners like HS2 to ensure disruption is kept to a minimum.

“We will continue to work closely with our partners to reduce the impact of the works on our roads and would like to thank road users and local communities for their patience.”

HS2 services will run between London and the West Midlands on a dedicated high-speed line before reaching destinations further north via the existing West Coast Main Line.