Engineers working for the HS2 project claimed a UK-first over the weekend when they successfully slid an enormous 4,600-tonne viaduct across the M6 without closing the motorway – significantly reducing disruption to drivers.

The 17 hour-long operation was the culmination of a three-stage process to assemble and 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.

To deliver this, they initially closed the M6 overnight between Junctions 4 and 5 on Thursday 11 December to shift the viaduct slightly forward by 12 metres. This was to ensure that both ends of the enormous beam were fully supported on concrete piers during this weekend’s slide.

The viaduct was then pushed the rest of the way across the busy motorway on Saturday at a speed of 13 metres per hour, with only the M42 slip closed during the weekend.

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.

Caroline Warrington, HS2 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.”

Mark Wild, HS2 chief executive, is currently leading a comprehensive reset of the programme – making sure the new railway is built as efficiently as possible and for the lowest reasonable cost. Over the last year, HS2 has focused on safely boosting levels of productivity across the construction programme.