The operation involved installation of a bridge to carry the HS2 high-speed railway over the M42 motorway. The team from HS2’s construction contractor Balfour Beatty Vinci (BBV) – slid the structure more than 160m.

The 86m-long structure, which has a base, three walls and top slab, was built over the last six months on land next to the motorway. The sliding mechanism, designed by Freyssinet, allowed the box to be pushed into place over the motorway on a guiding raft over a distance of 163m.

The structure was developed by a design joint venture of Mott MacDonald and Systra, working on behalf of BBV.

The site team worked around the clock to move HS2’s Marston Box bridge into place during the Christmas period. The operation took 40 hours, at a speed of 4m per hour, from 24 to 26 December, during a 10-day closure of the motorway.

The bridge was slid into place over the motorway

The motorway is on schedule to reopen early on 3 January 2023.

HS2 Ltd’s civils delivery director, Mike Lyons, said: “This is the first box slide of its kind over a motorway in the UK, and we believe it’s also the world’s longest slide, so it’s a great achievement for HS2 as we quickly approach peak construction. It’s fantastic to celebrate another big milestone for a project that is already providing work for almost 30,000 people today, and in the future, it will encourage people to use zero carbon public transport.”

On completion, the whole structure will be about 190m in length.

This construction method, which allowed it to be moved into place in one movement meant only two one-week closures of the motorway over a 12-month period.

Sasan Ghavami, Balfour Beatty Vinci’s construction director for the project, said: “We’re extremely proud to have successfully delivered the world’s longest box slide. It’s a huge achievement for our project team and everyone connected with Balfour Beatty Vinci.

“We’ve used innovative construction techniques and worked tirelessly throughout the Christmas period to move this 12,600-tonne bridge over the M42 motorway – all done with the aim of keeping disruption to an absolute minimum.”

The box slide operation is part of HS2’s 550,000m2 site at Kingsbury, where over 1,000 people are currently working. About 6,800 people are already employed in HS2’s construction in the West Midlands, with further jobs supported through the wider supply chain.

HS2 and BBV worked in partnership with National Highways.