National Highways is undertaking £27m of ‘vital upgrade work' on the Thelwall Viaduct, which carries upwards of 180,000 vehicles a day on the M6 across the Manchester Ship Canal and the River Mersey.

Starting this month, the strategic road authority will be replacing bridge joints on both the north and southbound structures in Lymm, Warrington. 

National Highways stated that replacing these joints is ‘essential to keep the bridge working safely and effectively', to reduce the risk of unexpected closures, and minimise disruption for road users.

Work is expected to start today, with scaffolding being installed underneath the bridge for access to the joints to allow overnight work on the M6 to start on 28 September between junctions 20 and 21. The project is due to be completed by winter 2027/28.

A constant contraflow system will be used from 12 October from just after junction 20 to 21 on the northbound carriageway and from just before junction 21 to before junction 20 on the southbound carriageway. National Highways says that this is the safest way to carry out work while keeping disruption ‘as low as possible and significantly reducing the number of motorway closures'.

As well as a contraflow system, National Highways will also implement a temporary 40mph speed limit and narrow lanes. It added that all lanes will remain open during the day, but only one lane will be open overnight on the carriageway it works on.

The scheme forms part of the Government's third Road Investment Strategy, which has allocated £8.4bn for resurfacing carriageways and renewing bridges between 2026 and 2031.

Chris Court, programme delivery manager at National Highways, said: ‘Our road network is ageing, and many key structures, including Thelwall Viaduct, were built several decades ago. The viaduct's joints have now reached the end of their operational lifespan, making replacement essential to maintain safety and reliability for road users.

‘This investment will help secure the long-term future of the structure, ensuring this vital route remains safe, resilient and fit for purpose. A well-maintained road network is crucial for supporting businesses, creating employment opportunities and driving regional economic growth.'