Specialist weld tests have been carried out on four of the five with the last tests presently underway.

The roads agency said its assessment indicated no immediate safety risk to road users, although National Highways has imposed restrictions preventing abnormal load movements on the bridges.

The biggest of the projects was for Costain on its A1 Birtley to Coalhouse contract, near Gateshead. The Allerdene bridge weighs in at 3,400t and spans the West Coast Main Line.

Allerdene bridge when under construction, which opened to traffic in September 2023

The 155m long, three-span composite bridge structure is formed from 16, 2.4m deep plate girders that were fabricated on Severfield’s automated T&I machine in Lostock.

Another big project delivered for Skanska involved two road bridges across the M42 to create a new junction 5a for Solihull Road to support access to Birmingham International airport and train station.

M42 junction 5a bridges

Also in the Midlands, the flyover at the A46 Binley junction in Coventry has been identified in the safety alert.

The 135m four-span bridge built for contractor Octavius forms part of the A46 Coventry junctions upgrade programme, which aims to address major bottlenecks on the strategic road link between the East and West Midlands. It was opened in February 2023.

This project involved installing around 32 beams weighing around 720t.

A46 Bindley Junction

The two other smaller bridge projects assessed by National Highways include the 38m-long Catherine De Barnes bridge spanning the new A4545 link road in the Midlands and the 42m-long Tolgroggan bridge on the A30 in Cornwall for main contractor Costain.

National Highways said it was now assessing whether any further strengthening measures may be required.