Colne Valley Viaduct

About

The Colne Valley Viaduct is a railway bridge that will carry High Speed 2 over the Colne Valley Regional Park and the Grand Union Canal. It runs between Harefield in Hillingdon, Greater London and Denham in Buckinghamshire. At a length of 3.38 km (2.10 miles) and a weight of 116,000 tonnes, it is the longest railway bridge in the UK.

It is one of the largest single civil engineering works of High Speed 2. Trains will travel at about 320 km/h (200 miles per hour) on the bridge. A contract for the section of the railway pertaining to the viaduct was awarded during 2017 and the design concept was shown in January 2018.

Preparatory work commenced shortly thereafter, including a compulsory land purchase and the establishment of temporary facilities, including a factory, onsite. Construction of the viaduct began in March 2021, with the main deck completed in September 2024 and full completion of the bridge in September 2025. Protestors occasionally occupied the site, and allegations over the viaduct's aesthetic and environmental impact upon the area have been made.