Marston Box rail bridge crossing over the M42
Using innovative technology to dramatically reduce traffic disruption, Marston Box bridge will be 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. 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 structure will be approximately 190 metres in length, of which approximately 82 metres will be made up by the Marston Box.
Planned road closure of the M42 during Christmas 2021 for HS2 works on the Marston Box Bridge
We need to undertake work between junctions 9 (Dunton Interchange) and 10 (Tamworth Interchange) of the M42 this Winter to prepare the ground to enable the Marston Box Bridge to be moved into position in Winter 2022. To complete the preparatory works safely and efficiently, the least disruptive option requires a temporary full closure of both the M42 southbound and northbound, between Junctions 9 and 10, for 7 days.
The works we will complete in the closure this year will include:
- Removing the existing surface of the motorway where the bridge will be located
- Installing construction materials to create the foundations and improve the stability of the ground to support the weight of the bridge
- Replacing barriers and install additional safety barriers
- Removing and upgrading the existing drainage system
- Installing a new surface to enable the motorway to re-open to road users
We are working closely with National Highways (formerly Highways England) to plan and complete these works. To complete these works safely and efficiently we will close the M42 motorway from 9pm on Friday 24 December (Christmas Eve) to 9pm on Friday 31 December 2021 (New Year’s Eve).
A clearly signed diversion route will be in place over this period with advance signage in place to help remind motorists of the closure. The proposed route has been assessed as the most appropriate route for vehicle types and provides the most efficient and user-friendly route for diverted traffic.
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. This option would require three months of total overnight closures, narrow lanes and a reduced speed limit of 50mph to complete the works. These 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 have reviewed and developed the original design, focussing on reducing the impact on road users and improving safety for our workforce. This has resulted in a fundamental change to the construction method with the box structure now to be constructed to the side of the motorway and then pushed into place using a ‘box jacking’ technique, rather than being constructed in place.
Design and construction benefits
A unique construction method is being used to dramatically 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 10,000-tonne bridge ‘box’ structure will be built on land next to the motorway and then a hi-tech raft will then glide it into position. This results in only two one-week closures of the motorway over a 12-month period. Whilst this technology is used on railways, this will be the first box slide of its kind over a motorway in the UK.
A range of benefits will be achieved through the current design and construction method:
- Using the ‘box jacking’ technique to build the box structure means installation over the motorway can be carried out during two seven-day closures. Building it in place would have required 18 months of traffic disruption
- A reduction in night time disruption for local residents as the new construction period will avoid 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 will be reduced through less use of materials, particularly concrete, and concrete piles
- A reduced impact on the flow of groundwater following a change to the foundations for the Box Structure
The M42 Marston Box will be moved into position during a second short-term temporary closure planned in winter 2022.