Widening Thames Bray Bridge

Overview

The M4 is the main strategic route between London, the west of England and Wales. It connects people, communities, and businesses, carrying on average 130,000 vehicles per day. The future M4 Smart Motorway will be a technology driven approach to increase capacity and relieve congestion while maintaining safety. 

To accommodate the new M4 Smart Motorway some bridges needed replacement but others, such as the existing Thames Bray Bridge needed widening. As the most complex piece of engineering of the scheme, design, planning, and execution had to be all carefully studied. 

Described by Highways England as the “one of its most complex pieces of engineering to date”, the widening scheme involves fitting an extra lane in each direction on the Thames Bray Bridge, which has carried the motorway over the River Thames west of London since the 60’s. 

The bridge required an 8m extension of the existing three-span structure (11.5m + 82.3m +11.5m) on the north side of the bridge. This will be in the same style as the existing structure and will be complete and open for use in 2021. 

The steel beams were prefabricated into three sections, weighing nearly 300t in total, so they could be installed while keeping the time that the road need to be closed to an absolute minimum. 

The result is a perfectly integrated widened bridge, designed to behave in the same way as the existing structure while replicating the arched effect from an aesthetic perspective.