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An aerial of the world's longest box bridge slide across the M42 in Warwickshire.
An aerial of the world's longest box bridge slide across the M42.

Marston Box Rail Bridge

Marston Box will connect to Dunton Wood Embankment to the south and the Birmingham and Fazeley Canal Viaduct, which crosses the canal, to the north. The completed structure will be approximately 190 metres in length, of which approximately 82 metres is the Marston Box structure itself.

Using innovative technology to dramatically reduce traffic disruption, Marston Box bridge is the UK’s first ‘box-slide’ bridge over a motorway and will carry the HS2 line across the M42 motorway near junction 9, north of Lea Marston and Curdworth in North Warwickshire.

Bridge construction

A unique construction method is being used to reduce traffic disruption. The bridge was originally designed as a traditional structure, which would have created significant traffic disruption for motorway users, with three months of total overnight closures and around two years of reduced lane widths and 50mph speed limits.

Instead, the 12,000-tonne bridge ‘box’ structure was built on land next to the motorway and then a hi-tech raft glided it into position over a number of days, using a ‘box jacking’ technique. This resulted in only two one-week closures of the motorway over a 12-month period, dramatically reducing the impact on road users. The first closure happened in December 2021 for preparation work, and the second week-long closure happened in December 2022 to slide the bridge into place.

On Thursday 29 December, HS2 Ltd announced a world-first as around 450 people from our construction contractor in the Midlands – Balfour Beatty VINCI (BBV) – slid a 12,600 tonne bridge a record 165 metres to position it across a motorway in Warwickshire.

The innovative method dramatically cut disruption to road users and is part of HS2’s plan to reduce the impact of construction on local communities.

The site team worked around the clock to move HS2’s Marston Box bridge into place over the M42 during the Christmas period. The dramatic operation took 40 hours, at a speed of 4 metres per hour, from Saturday 24 to Monday 26 December during a 10-day closure of the motorway between Junctions J9 and J10 (northbound and southbound).

The Marston Box bridge was successfully installed and the road reinstatement completed on Sunday 1 January – 36 hours ahead of schedule.

National Highways re-opened the M42 Motorway in both directions, between junction 9 (Dunton Interchange) and junction 10 (Tamworth Interchange), on Sunday 1 January 2023.

We would like to thank everyone using the road network for their patience whilst these works were carried out.

Whilst this technology is used on railways, this was the first box slide of its kind over a motorway in the UK. A range of benefits were achieved through the current design and construction method:

  • Using the ‘box jacking’ technique to build the box structure meant installation over the motorway could be carried out during two short closures. Building it in place would have required 18 months of traffic disruption.
  • A reduction in night-time disruption for residents as the new construction period avoided the need for prolonged periods of night working.
  • The updated Box Structure design is smaller in size and will therefore have a reduced visual impact.
  • The carbon footprint for this structure is reduced through less use of materials, particularly concrete and concrete piles.

Improving safety and reducing impact on road users

The original HS2 Environmental Statement (ES) scheme design required the bridge to be constructed ‘in situ’ on a live motorway over a 20-month period. The lengthy closure periods would require a defined diversion route to be active for a three-month period, increasing traffic volumes, congestion and delays on the local road network.

We reviewed and developed the original design, focussing on reducing the impact on road users and improving safety for our workforce. This resulted in a fundamental change to the construction method with the box structure constructed to the side of the motorway and then pushed into place using a ‘box jacking’ technique, rather than being constructed in place.

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Archaeology

Archaeology

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Green Corridor

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Managing impacts of construction

Managing impacts of construction

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Construction look-ahead

Construction look-ahead

Read our three-month lookahead for associated work in Warwickshire.

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