HS2 Completes Civil Engineering on Record-Breaking Colne Valley Viaduct

New images have been released today to mark the completion of civil engineering works on HS2’s Colne Valley viaduct – the UK’s new longest rail bridge.

HS2 has announced the completion of civil engineering work on the Colne Valley viaduct, the new longest rail bridge in the UK.

Stretching 2.1 miles, the structure now surpasses Scotland’s Tay Bridge, which had held the record since 1887. The viaduct carries the high-speed line across lakes, roads, the River Colne and the Grand Union Canal, just north-west of London.

A Landmark Engineering Feat

Built by Align – a joint venture of Bouygues Travaux Publics, VolkerFitzpatrick and Sir Robert McAlpine – construction began in March 2021. Over the past three years, engineers installed 1,000 individually designed deck segments to create the viaduct’s gentle curve. The final pre-cast segment was lowered into place in September 2024.

Recent finishing works have included parapets, noise barriers, waterproofing, drainage, and a structural health monitoring system. The viaduct rises 10 metres above the valley floor and will eventually carry trains at speeds of up to 200mph.

Industry Reaction

Billy Ahluwalia, HS2 Ltd’s senior project manager for the viaduct, reflected on the scale of the achievement:

“The viaduct marks more than a decade of planning, design and construction. I’m immensely proud of the dedication shown by everyone involved. It’s a remarkable structure that will stand the test of time.”

Coralie Peroux, Align’s project director, highlighted the collaboration behind the milestone:

“Delivering the UK’s longest rail bridge was an immense technical challenge. Our integrated project team and supply chain rose to that challenge, producing an iconic landmark and a legacy for future engineers.”

Part of a Much Larger Programme

The Colne Valley viaduct is one of more than 50 major viaducts along HS2’s 140-mile route between London and the West Midlands. It lies between two of the line’s longest tunnels – the 8.4-mile Northolt Tunnel and the 10-mile Chiltern Tunnel.

Although the completion is a major milestone, much of HS2’s civil engineering programme remains unfinished. Chief executive Mark Wild has begun a reset of the scheme, aiming to deliver it at the lowest possible cost while maintaining efficiency.

What Comes Next

When operational, HS2 trains will run on dedicated high-speed tracks between London and Birmingham before continuing north on the existing rail network. The project is expected to ease congestion on the West Coast Main Line, increase capacity, and stimulate economic growth across the regions it connects.