HS2 completes impressive UK-first live M6 viaduct slide without motorway closure

The HS2 programme has reached a major civil engineering milestone with the successful installation of the east deck of the M6 South viaduct without closing the motorway to live traffic. Engineers completed the 315 metre lateral slide of the 4,600 tonne structure using a fully restrained launch method, which is believed to be a first for a UK motorway.

The operation marked the final stage of a three phase bridge launch and was completed over a 17 hour period. Earlier stages required full weekend closures of the M6, but lessons learned enabled the final movement to take place above flowing traffic, significantly reducing disruption for road users. Only a short overnight closure and a slip road restriction were required to prepare the structure for its final position.

The works were delivered by Balfour Beatty VINCI in close coordination with National Highways. The deck was assembled offline beside the motorway and slid into place using strand jacks operating over low friction sliding pads. This approach allowed precise control of alignment, load transfer, and structural stability throughout the operation.

Structurally, the viaduct comprises a hollow double box deck fabricated from weathering steel, selected to reduce long term maintenance requirements. The deck is supported by reinforced concrete piers, with the tallest reaching nearly 10 metres. Precast deck slabs were installed prior to the launch, reducing the need for future motorway closures during finishing works.

With the east deck now complete, the project has reached its halfway point. A parallel west deck will be assembled and launched using the same method during 2026, demonstrating how construction innovation can deliver large scale infrastructure while minimising public disruption.

Check out the impressive installation in the following video.