Engineers will close the eastbound M8 through central Glasgow for extended periods between Friday night and Monday morning while they jack part of the Woodside Viaduct away from the concrete structures that have supported it for more than half a century. The operation is one stage in a repair programme that began after inspections found the motorway’s supports were in substantially worse condition than expected.
Late on Friday night, traffic will be removed from a section of the M8 through Glasgow and engineers will begin transferring the weight of part of the motorway from the structures on which it normally rests.
The work will take place on the Woodside Viaducts between Junction 18 at Charing Cross and Junction 16 at Craighall.
Amey, working for Transport Scotland, will jack two triangular crosshead bridge supports beneath the eastbound carriageway.
The eastbound motorway will close between Junctions 18 and 16 from 10pm on Friday 4 September until 11am on Saturday, again from 10pm on Saturday until 6am on Sunday, and from 7pm on Sunday until 6am on Monday.
The westbound motorway will remain open.
Traffic travelling east from further west will be directed towards the M74 and M73. Traffic joining closer to the city centre will use local diversions before returning to the motorway.
The closures are required because the operation involves one of the more unusual engineering procedures now taking place beneath Scotland’s motorway network.
The viaduct is being lifted sufficiently for its load to be transferred from deteriorated elements of the original structure into a temporary steel support system.
Once that transfer has been completed, engineers can work on the concrete structure without requiring it to continue carrying the full motorway load above.
This weekend’s operation forms part of a programme involving 23 separate supports beneath the Woodside Viaducts.
The temporary works alone are currently estimated at between £126 million and £152 million.
They are not the permanent repair.
The motorway above Woodside opened in 1971
The Woodside Viaducts belong to a particular period in Glasgow’s history.
After the Second World War, planners were attempting to redesign a city built largely around nineteenth-century streets for rapidly increasing motor traffic.
Robert Bruce’s First Planning Report of 1945 proposed extensive reconstruction of central Glasgow. By the early 1960s, Glasgow Corporation had commissioned detailed proposals for an Inner Ring Road.
Scott Wilson Kirkpatrick and Partners produced the engineering proposals for its northern section.
The north and west flanks of the Inner Ring Road were approved in 1965.
Construction followed in stages.
The Woodside section was delivered through two principal contracts between 1967 and 1971.
Its second stage was dominated by elevated motorway.
Two multi-span viaducts, approximately 365 metres and 460 metres long, were constructed above the existing city.
The elevated design allowed roads including Garscube Road to remain beneath the motorway and enabled the route to cross an already developed urban area.
The viaduct beams were precast from post-tensioned concrete. Individual beams weighed as much as 80 tonnes.
They were supported on reinforced-concrete pierheads carried on piles or concrete foundations.
A casting yard was established beside the works so that large numbers of beams could be manufactured close to the motorway construction site.
By mid-1970 the beams had been installed.
The Woodside section opened in May 1971.
The original construction contract cost about £4 million, equivalent to roughly £50 million in 2023 prices according to the Scottish Roads Archive.
More than half a century later, the temporary engineering now required beneath the viaducts is expected to cost more than twice that inflation-adjusted figure.
Inspections found the supports were in worse condition than expected
The present works began with investigations undertaken in 2020 and 2021 ahead of planned refurbishment.
Engineers carried out intrusive inspections of the viaduct supports.
Transport Scotland says those inspections found that the crossheads were in a much worse condition than anticipated.
Traffic restrictions followed in March 2021.
Lanes were narrowed and slip roads restricted to reduce the load being carried by the structures.
Those restrictions have remained part of the operation of the motorway while temporary support systems have been designed and installed beneath it.
The affected structural elements include half-joints.
A half-joint is a structural arrangement in which the end of one section of a bridge is reduced in depth and supported on a corresponding projecting section of another structural element.
The arrangement can create a compact connection between bridge sections, but it concentrates significant forces into a relatively small area.
The Woodside programme requires the load to be taken away from the affected joints before repairs can be carried out.
That is the purpose of the jacking operation.
The motorway cannot simply be supported from anywhere underneath
Supporting an elevated motorway would be complicated on an empty site.
Woodside is not an empty site.
Beneath the motorway is another layer of Glasgow infrastructure.
Water mains, gas infrastructure, sewers, streets and other services occupy the ground around the viaduct columns.
The Glasgow Subway also passes beneath the area.
Transport Scotland says four of the locations around the subway tunnels require specially designed structures so that the load from the motorway can be transferred to ground outside the tunnel footprint.
Another support requires a steel collar around the existing columns because of underground services nearby.
Each of the 23 locations requires an individual propping design.
Column heights differ.
Span lengths differ.
The widths of the structures differ.
The loads being transferred therefore differ.
The ground beneath them is also occupied by infrastructure constructed at different periods and recorded to different standards.
An underground sewer was not where the drawings said it was
One of the problems encountered during the works demonstrates the difficulty of rebuilding infrastructure inside a city whose underground systems have accumulated over generations.
In spring 2025, engineers discovered a sewer beneath planned piling works.
It was not in the location shown on the available record drawings.
The sewer was also close to the Subway.
The discovery required changes to the work and contributed to delays in the westbound propping programme.
Transport Scotland has said inaccurate records of underground utility infrastructure have repeatedly complicated the project.
The motorway is consequently being repaired in an environment where engineers have to account not only for the original bridge but for infrastructure beneath it that may not correspond precisely with historical records.
The problem is not unique to Glasgow.
Major infrastructure projects in older cities frequently encounter utilities whose location, depth or condition differs from archived plans.
At Woodside, the consequence is magnified because new foundations intended to carry motorway loads cannot be placed through an existing sewer, water main or subway tunnel.
The motorway carries about 150,000 vehicles a day
Transport Scotland estimates that approximately 150,000 vehicles use the Woodside Viaducts each day.
The route forms part of the principal east-west motorway through Glasgow and connects with the wider M8, M74, M77 and M80 network.
Closing the structure for the duration of the repair programme was therefore not the approach selected.
Instead, the temporary propping system has been constructed while traffic continues to use the motorway above.
That decision has shaped much of the engineering.
Construction space is limited.
Work has to coexist with traffic.
Local streets remain in use.
The Subway must continue operating.
Utilities must remain protected.
The motorway itself cannot carry unrestricted traffic until the temporary support system is sufficiently complete.
The jacking taking place this weekend is intended to move the eastbound structure closer to that point.
Jacking transfers the motorway load into temporary steelwork
The engineering principle is relatively direct.
The execution is not.
Temporary steel supports are constructed beneath the viaduct.
Hydraulic jacks then apply controlled force to the bridge structure.
As the jacks take the load, weight is transferred away from the original support and into the temporary system.
The structure is not being raised to create a visibly higher motorway.
The movement required is controlled and limited to what is necessary to transfer the structural load.
Once the transfer is complete, the deteriorated half-joint can be repaired without continuing to carry the same load from the carriageway above.
After permanent structural repairs are eventually completed, the temporary jacks and propping can be removed.
This weekend’s work concerns two triangular crosshead supports on the eastbound viaduct.
The closure provides the conditions required to undertake that load transfer without live traffic on the affected carriageway.
The temporary repair has become a major infrastructure project of its own
The first groundworks for the temporary propping began in August 2021.
The first props were installed in February 2022.
Transport Scotland initially expected a substantially shorter programme.
As engineering information developed, both the cost and timetable increased.
By May 2024, Transport Scotland was estimating the temporary works at between £126 million and £152 million.
The same cost range remains current.
The completion timetable has also moved.
Transport Scotland now expects the eastbound propping and jacking to allow lane restrictions to be removed in autumn 2026.
The westbound temporary works are expected to continue into the second half of 2027.
Those dates remain subject to construction conditions, weather and further underground or structural discoveries.
The £152 million does not buy Glasgow a permanent solution
The temporary support programme is intended to allow the motorway to return to full traffic capacity and permit more extensive repairs.
Transport Scotland is separately developing the permanent intervention.
Technical advisers were appointed in 2025 to examine long-term options.
The permanent project is currently at business-case and design-development stage.
Transport Scotland held public engagement on early options in February 2026.
The permanent cost has not yet been established.
The agency says a procurement strategy is being developed and that a cost estimate will be produced to inform the appointment of a contractor.
The eventual solution therefore sits beyond the £126 million to £152 million currently associated with temporary propping.
The temporary system stabilises the viaducts and permits repairs to proceed.
It does not settle how Scotland intends to maintain or replace these structures over the longer term.
Glasgow’s motorway was designed during a different phase of the city
The Woodside Viaducts were built as part of Glasgow’s Inner Ring Road programme.
Only the north and west flanks of the proposed ring were ultimately constructed.
The motorway reflected the transport assumptions of its period: rising private car ownership, expanding road traffic and large-scale reconstruction of urban transport networks.
Its construction also changed the physical city.
Elevated roads crossed established neighbourhoods and altered street patterns.
The wider Inner Ring Road programme was associated with the extensive redevelopment taking place across central Glasgow during the 1960s and 1970s.
Woodside’s elevated motorway was designed to preserve some surface routes beneath it, but the structure itself became a permanent division within the urban landscape.
That history now creates an infrastructure inheritance.
The motorway exists.
It carries traffic volumes of national significance.
Communities and streets exist around and beneath it.
The Subway passes underneath it.
Replacing, rebuilding or substantially altering it would have consequences extending beyond bridge engineering.
Scotland has a generation of infrastructure reaching this age
The Woodside Viaducts are not alone in reaching the later decades of their design life.
Large parts of Scotland’s motorway, bridge and trunk-road infrastructure were constructed during the major road-building period from the 1960s through the 1980s.
The Kingston Bridge opened in 1970.
The Woodside section followed in 1971.
Sections of the M8, M9, M90 and other strategic roads belong to the same broad infrastructure generation.
Concrete structures require inspection, maintenance and periodic intervention throughout their lives.
Traffic loading, water ingress, road salt, reinforcement corrosion, joint deterioration and the behaviour of materials over decades all influence condition.
The engineering challenge increasingly involves maintaining infrastructure while it remains heavily used.
Building a new road across an undeveloped site and repairing a fifty-five-year-old elevated motorway above a functioning city are different forms of construction.
Woodside belongs to the second.
This weekend is one operation inside a project that will continue for years
The eastbound closures begin at 10pm on Friday.
For traffic approaching Glasgow from the west, the principal strategic diversion will use the M74 and M73.
Vehicles joining around Anderston and Charing Cross will be directed through local roads before returning to the M8.
Emergency services, bus operators, Glasgow City Council and Transport Scotland have coordinated arrangements for the closures.
Football clubs with fixtures during the weekend have also been contacted because of the effect on journeys through Glasgow.
By Monday morning, the motorway is scheduled to reopen.
The engineering beneath it will continue.
Completion of the eastbound temporary propping is currently expected later this year. Work on the westbound structure is expected to continue through 2027.
After that comes the permanent intervention.
The Woodside Viaducts opened in May 1971 as part of the infrastructure intended to carry Glasgow into the motorway age.
In September 2026, engineers are temporarily transferring sections of that motorway onto new steel structures so that the concrete beneath can be repaired.
The operation taking place this weekend lasts several nights.
The decision about what Glasgow ultimately does with the viaducts will last considerably longer.
SOURCES
M8 Woodside Viaducts | Eastbound Overnight Bridge Jacking Works — Traffic Scotland — September 2026 — https://www.traffic.gov.scot/travel-news/projects-and-events/m8-woodside-viaducts-eastbound-overnight-bridge-jacking-works
M8 Woodside Viaducts — Temporary Propping: Project Details — Transport Scotland — updated 2026 — https://www.transport.gov.scot/projects/m8-woodside-viaducts-project/m8-woodside-viaducts-temporary-propping/project-details/
M8 Woodside Viaducts Project — Transport Scotland — updated 2026 — https://www.transport.gov.scot/projects/m8-woodside-viaducts-project/
M8 Woodside Viaducts — Permanent Work: Project Details — Transport Scotland — updated 2026 — https://www.transport.gov.scot/projects/m8-woodside-viaducts-project/m8-woodside-viaducts-permanent-work/project-details/
Challenges Encountered at M8 Woodside Viaducts — Transport Scotland — 28 August 2025 — https://www.transport.gov.scot/news/challenges-encountered-at-m8-woodside-viaducts/
National Transport Strategy: Fifth Delivery Plan — Transport Scotland — 2026
