Innovative M6 bridge slide for HS2 completed without motorway closure

A UK-first was completed over the weekend, when an enormous 4,600-tonne viaduct was slid into place over the M6 without the motorway being closed. 

As part of the HS2 project, the 17-hour-long operation marked the culmination of a three-stage process to install the 315-metre East deck of the M6 South viaduct, which will carry high-speed trains heading to Birmingham and further north. 

While the previous slide had required a weekend closure of the main carriageway, the team – led by HS2’s main work contractor Balfour Beatty VINCI (BBV) – worked closely with National Highways to develop the ‘fully restrained’ process which allowed them to safely slide the final section above the moving traffic. It is thought to be the first time this technique has been used on a UK motorway. 

The structural design was delivered by the Mott MacDonald SYSTRA, plus WW+P Architects, Design Joint Venture (DJV). 

The successful operation means the project to construct the M6 South viaduct has reached the halfway point. Over the next year, the same process will be repeated, with a parallel West deck slid into position alongside the first one to carry trains heading south. 

Jack Hillier, Senior Project Manager at SYSTRA, said: “Once more our dedicated team from across the Mott MacDonald SYSTRA DJV have played their part in a significant milestone for the HS2 project. 

“The dedicated design work that has been delivered enables this innovative construction method to be successfully implemented, and it is a proud moment for everyone involved.  

“Every element of work on the project is brought to life through a collaborative approach with safety and innovation at heart, and we look forward to next year’s progress.” 

Caroline Warrington, HS2 Ltd’s Head of Delivery, said: “Along the HS2 route we are pioneering new approaches to engineering and construction in order to deliver more efficiently and with less impact on our neighbours. 

“We believe this fully restrained slide was a first for the country, but most importantly it means we’ve been able to cut in half the number of times we’ve had to close the motorway. I’d like to thank everyone who worked so hard to make the operation a success.” 

Russell Luckhurst, the BBV engineer leading the delivery of the works, said: “We’re all feeling a huge sense of pride after sliding a 4,600-tonne viaduct into its final position this weekend. The third and final slide of the East deck viaduct was delivered over a live motorway for the first time in the UK, making this achievement even more special. 

“Using this ‘fully restrained’ technique meant we were able to keep disruption to an absolute minimum. Our focus will now turn towards the neighbouring West deck viaduct, which will be launched in multiple phases throughout 2026, as well as the East deck finishing works.” 

Click here for more about SYSTRA’s work on HS2 and other high speed rail projects.