Britain Completes Construction of Its Longest Rail Bridge

The civil engineering works for the Colne Valley viaduct, now the UK’s longest rail bridge, have officially been completed. Spanning 2.1 miles (3.4 km), the structure will carry HS2’s high-speed railway across roads, lakes, the River Colne, and the Grand Union Canal. Designed for trains running at 200 mph, the viaduct’s sweeping curve is formed from 1,000 uniquely engineered deck segments.

Construction began in March 2021 and the last pre-cast deck segment was installed in September 2024, after which the focus shifted to finishing elements such as parapets, waterproofing, drainage, and noise barriers. Structural health monitoring systems were also installed to track performance during operation. Standing 10 metres tall, the viaduct surpasses the Tay Bridge, which held the record as Britain’s longest rail bridge since 1887.

The Colne Valley viaduct is one of over 50 major viaducts being constructed along the HS2 route between London and the West Midlands. It sits strategically between the 8.4-mile Northolt Tunnel and the 10-mile Chiltern Tunnel. Beyond its technical importance, the viaduct demonstrates advances in collaborative project delivery and large-scale pre-cast segmental construction. The project represents a benchmark in integrating structural safety, sustainability, and long-term monitoring in modern rail infrastructure.

Impressive aerial footage of the bridge is shown in the following video.