National Highways Launches £50M M5 St Georges Bridge Upgrade as UK Road Infrastructure Renewal Accelerates

National Highways is set to invest more than £50 million into a major refurbishment programme for the M5 St Georges Bridge in North Somerset, as the organisation continues to address the growing challenge of maintaining ageing strategic road infrastructure across England.

The extensive programme of works will focus on strengthening and modernising the bridge structure, which carries around 100,000 vehicles per day over a railway line near Junction 21 for Weston-super-Mare.

The project highlights the increasing scale of investment now required across Britain’s motorway network, much of which was originally constructed during the 1960s and 1970s and is now reaching a critical stage in its operational lifespan.

National Highways says the scheme is designed to extend the bridge’s long-term resilience while reducing the likelihood of future emergency repairs and unplanned closures.

The work will involve complex engineering operations, including structural concrete repairs, resurfacing, waterproofing, drainage improvements, and the replacement of 72 bridge bearings — the components that allow the structure to move safely under traffic and temperature changes.

As part of the programme, engineers will also lift the bridge structure dozens of times in order to replace the ageing bearings beneath it. Steel beams underneath the bridge will be repainted, barriers replaced, and sections of the bridge structure renewed.

Alongside the bridge refurbishment itself, National Highways will also improve the northbound entry slip road by introducing a second merge lane onto the M5 to help ease congestion in the area.

Despite the scale of the works, the organisation says three lanes of traffic will remain open in each direction throughout the project using a long-term contraflow system and reduced speed limits. A 50mph restriction is expected to remain in place for much of the construction period from autumn 2026 through to late 2029.

Maintaining live motorway traffic while carrying out major structural repairs above an operational railway adds significant complexity to the scheme. National Highways says the work is being closely coordinated with Network Rail to ensure rail services beneath the bridge can continue operating safely during construction.

Terry Robinson, Engineering Lead for National Highways, said many of the country’s key motorway structures are now reaching an age where significant renewal work is becoming unavoidable.

The project forms part of the government’s wider £27 billion Road Investment Strategy, which includes £8.4 billion allocated between 2026 and 2031 for carriageway resurfacing and bridge renewals across the strategic road network.

The St Georges Bridge scheme reflects a wider shift taking place across UK infrastructure investment, where the focus is increasingly moving from expansion toward asset renewal, resilience, and long-term operational reliability.

Large sections of the UK motorway and trunk road network were built rapidly during periods of major post-war infrastructure expansion. While many of these assets were designed for decades of use, the scale of modern traffic demand combined with ageing materials means extensive maintenance and structural renewal programmes are now becoming increasingly common.

Projects such as St Georges Bridge also demonstrate the engineering challenge of upgrading critical infrastructure while keeping the network operational. With traffic volumes remaining high and disruption needing to be minimised, infrastructure operators are increasingly required to deliver complex renewal programmes within highly constrained live environments.

Early preparatory works have already begun on site, with the next phases expected to include void filling beneath carriageways, resurfacing activity, and overnight closures ahead of the main structural repair programme.