Video shows 'engineering world first' as 12,600 tonne bridge slides into place over M42 in Warwickshire

A 12,600 tonne bridge has slid into place over the M42 in Warwickshire, in what engineers are describing as a 'world first'.

Around 450 people from HS2’s construction contractor in the Midlands – Balfour Beatty VINCI (BBV) – moved the bridge a record 165 metres to position it across a motorway.

The site team worked around the clock to move HS2’s Marston Box bridge into place over the Christmas period. The operation took 40 hours, at a speed of four metres per hour, from Saturday December 24 to Monday December 26 during a 10-day closure of the motorway between Junctions J9 and J10 (northbound and southbound). The motorway is on schedule to reopen at 5am on Tuesday January 3.

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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."

Over the last six months, the giant 86 metre-long structure was built on land next to the motorway. The structure, developed by a Design Joint Venture of Mott MacDonald and Systra, working on behalf of BBV, has a base, three walls and top slab.

The sliding mechanism, designed by specialist civil and structural engineering company Freyssinet, allowed the box to be pushed into place over the motorway on a guiding raft over a distance of 163 metres – which is believed to be the world’s longest box slide.

On completion, the whole structure will be around 190 metres in length, and will carry HS2 over the motorway as it heads north to Crewe, or on its southward journey as it loops into Birmingham Curzon Street or continues straight on to Interchange Station in Solihull, Old Oak Common Station and London Euston.

Once built, the railway bridge will connect to Dunton Wood Embankment to the south and the Birmingham and Fazeley Canal Viaduct, which crosses the heritage canal, to the north.

A spokesperson for HS2 said: "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, dramatically reducing disruption for road users."

National Highways senior network planner, Frank Bird, said: “We’d like to say a big thank-you to motorists for their patience during the closure of the M42. It’s never easy to close a busy motorway such as the M42 for an extended period of time but it has been vital to ensure the safety of the workforce and motorists while this work is taking place.

“We’ve been working collaboratively with HS2 for the past 18 months to ensure the operation ran smoothly and to help keep disruption to a minimum for drivers. The installation of the new Marston Box bridge is a significant milestone in the HS2 project and it’s great to see it finally in place.”