National Highways is to begin the main phase of a £27m scheme to replace expansion joints on the Thelwall Viaduct, with a 24/7 contraflow and 40mph speed limit introduced on the M6 from Monday 12 October.
The viaduct carries the motorway across the Manchester Ship Canal and the River Mersey at Warrington. More than 180,000 vehicles use the crossing each day.
Overnight closure before contraflow begins
The northbound carriageway will close completely overnight on Sunday 11 October while the traffic management layout is installed. From the following day, the contraflow will run between junction 20 at Lymm and junction 21 at Woolston.
During the daytime, northbound traffic will have four lanes available: three on the northbound carriageway and one transferred to the southbound side. Southbound traffic will retain four lanes on its own carriageway.
Northbound traffic will be reduced to one lane between 10pm and 5am. The northbound exit slip road at junction 21 is expected to remain open throughout. Narrow lanes, the 40mph limit and average-speed cameras will remain in place during each phase.
Work to be delivered in two phases
The first phase will replace the joints on the northbound structure and is scheduled to continue until spring 2027. The traffic management arrangement will then be switched so that work can take place on the southbound structure. National Highways expects the full scheme to be completed in winter 2027/28.
Expansion joints allow a bridge deck to move as temperatures change and as it responds to traffic loads and wind. National Highways said the existing joints have reached the end of their operational lifespan and that replacement is needed to maintain safe operation, reduce the risk of unplanned closures and limit disruption to road users.
A National Highways spokesperson described the contraflow as “the safest way to carry out work” while keeping disruption low and significantly reducing the number of motorway closures.
Enabling work beneath the viaduct at Warrington Road began on 1 September, followed by overnight closures to install traffic management between 28 September and 1 October.
The scheme forms part of the third Road Investment Strategy, covering 2026 to 2031, which includes £8.4bn for carriageway resurfacing and bridge renewal.