Marston Box Rail Bridge

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

The dramatic operation took 40 hours, at a speed of 4 metres per hour, from Saturday 24 to Monday 26 December during a closure of the motorway between junctions 9 and 10 (northbound and southbound). The bridge was successfully installed, and the road reinstatement completed, on Sunday 1 January – 36 hours ahead of schedule.

Bridge design

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

The original design was reviewed, 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 being constructed to the side of the motorway and then pushed into place using a ‘box jacking’ technique, rather than being constructed in place.

The updated box structure design is smaller in size and therefore has a reduced visual impact. It also means a reduced carbon footprint through less use of materials, particularly concrete and concrete piles.