Repair, replace or demolish? The costly future for Glasgow's M8 viaducts

Demolishing a section of Scotland's busiest motorway in Glasgow is one of three options being considered due to the deterioration of two elevated bridges.

Temporary work to the Woodside Viaducts which carry the M8 on the north side of the Kingston Bridge has been ongoing for several years at a cost of £152m.

Transport Scotland is now consulting on options for a more permanent fix, with the cheapest being to remove that section of the motorway entirely and re-route traffic via the M74.

The other two options are to either repair or replace the viaducts, which would be more expensive and take longer.

The viaducts, at Junction 16 Craighall and Junction 17 Charing Cross, were completed in 1971 and now carry around 150,000 vehicles a day along the northern edge of the city centre.

They have been supported by extensive temporary propping since 2021 after engineers identified serious deterioration in the load‑bearing structures.

While the temporary works have kept the motorway open, they have reduced lane capacity and lowered speed limits.

Transport Scotland said these measures were not a viable long‑term solution due to maintenance demands and the amount of space the props occupy.

As part of its strategic review, Transport Scotland is considering three options: repairing the viaducts, replacing them, or removing them entirely.

Removing them would require the closure of part of the M8. Under this scenario, all through‑traffic would be rerouted via the M74 on the south side of the city.

Officials estimate it would cost less than £125m and take 1-2 years to complete.

However, a report noted that the M74 is already operating near capacity, raising questions about how well it could absorb the extra diverted traffic.

Repairing the viaducts could cost from £125m to £200m and take up to three years to complete.

The most expensive option, estimated at £200m-£500m, would be to replace them completely and the work could last up to four years.

Transport Scotland acknowledged that removing a section of the motorway would likely cause significant disruption, with major impacts on congestion, journey times and resilience across the wider road network.

A Transport Scotland spokesperson said: "We are keen to hear the thoughts of the local communities and road users on the permanent solution for the M8 Woodside Viaducts project.

"Public engagement events are being held to provide local communities and road users with the opportunity to learn more and to share their feedback on the options."