M8 in Glasgow: Why are roadworks on Scotland's busiest motorway taking so long?

Transport bosses have told STV News that roadworks on a section of the M8 are the “biggest on their books” after three-and a-half-years of delays for drivers – and repairs yet to even start.

Temporary propping works at the Woodside Viaducts in Glasgow began in March 2021 after the bridges’ supports were found to be in worse condition than expected.

Those initial works are not scheduled to be finished until early 2026, with the estimated cost now as high as £152m.

Costs and timescales for the repair works after that are still to be determined, with a contractor yet to be appointed.

Inspections in 2020 found the condition of the motorway bridges' supports to be worse than expected. — Inspections in 2020 found the condition of the motorway bridges’ supports to be worse than expected. STV News

What do the current works involve?

Lane and speed restrictions have been in place since work started three years ago, with an estimated 150,000 vehicles travelling over the Woodside Viaducts daily.

The temporary propping works have involved building structures to take the load of that traffic off the existing supports, in order for them to be repaired.

In total, 23 areas need to be propped – but this work has become increasingly complex and costly.

So far, props have been installed to 13 of those locations, with eight of these having been jacked to take the load off the existing supports.

The temporary propping works under the M8 have themselves seen delays and cost overruns. STV News

Varying ground conditions have also affected the project, with engineers having to negotiate several of Glasgow’s underground public utilities and the city’s subway tunnel.

“Every location is unique in its own right,” Andy Dickson, project manager for Amey, said.

“The depths of the existing foundations, the dimensions of those are different in every location. Indeed, the supports themselves are unique.

“There’s circa 10km of concrete piles, there’s in the region of 4,500 tonnes of steel being installed on the project, 3,000 cubic metres of reinforced concrete. In terms of scale, it’s fairly significant.

“There’s a multitude of public utilities and services within the area – many of which we’ve had to divert, many of those weren’t in existence at the time the viaduct was built and they’ve been diverted. Many of the really significant ones, we’re unable to divert because of the significance of them.

Andy Dickson, project manager, says thousands of tonnes of steel are being installed STV News

“We’ve a 36-inch old water main running down Garscube Road and 275kva ultra-high voltage power cables that couldn’t be diverted, which gives rise to this very bespoke propping solution that avoids interfering with those particular utilities.

“A major influencing factor on the design has been the presence of the SPT subway tunnel, the third oldest subway tunnel in the world, I believe it is, that’s at the western end of the site, and that has hugely impacted the design and the solution that we’ve brought to bear at that end of the site.

“We’re installing concrete piles within metres of that existing subway tunnel and in doing so we’ve had to maintain the integrity of the tunnel throughout that whole process.”

When will the restrictions be lifted?

Transport Scotland expects the temporary propping works to be completed in early 2026, and hopes to lift lane restrictions on the motorway’s eastbound carriageway in early summer 2025.

All lane restrictions are due to be lifted in early 2026, with hopes the eastbound carriageway's can be removed earlier — All lane restrictions are due to be lifted in early 2026, with hopes the eastbound carriageway’s can be removed earlier STV News

Plans for any restrictions during the repair works will be released in due course, but bosses say they will be taking place “mostly below” the motorway.

Dr Hazel McDonald, Transport Scotland’s chief bridge engineer, said: “This is the biggest scheme I’ve got on my books.

“We look after 5,500 structures and these are only two. Obviously, it’s very disruptive to traffic and the local community and businesses and it’s a big challenge here.

“The restrictions are planned to be off by 2026. The eastbound viaduct will open earlier than that, which is the one that’s causing most disruption to drivers.

Chief bridge engineer. Dr Hazel McDonald, says the Woodside Viaducts works are the “biggest on her books” STV News

“There is an ongoing process to go through the options and procurement for repairs and once a contractor is appointed we’ll know further about costs and timescales for the repairs, which will be going on mostly below.

“I would like to thank drivers and the community and businesses for their patience. We really appreciate that it is very disruptive to them, but I hope they can understand the complexity of the work that we’re doing here and although there’s not much to see up top, there is plenty going on round here.

“I’ll be pleased to see the four lanes opened in both directions and to relieve traffic congestion on this section of the motorway. Obviously, we have 150,000 vehicles traversing this section of the route every day.

“The majority of the structure is in really good condition, it’s the areas where we’re supporting the beams that need to be repaired and most of that work will be done from underneath, and we will minimise any disruption up top once it’s opened.”