The roughly 21 bridge structures which support the carriageway and slip roads along that section of the A40 Westway were built between 1969 and 1970 using reinforced concrete.
The Westway is a key strategic route and one of the busiest on TfL's road network. It's normally used by around 96,000 vehicles a day.
Major maintenance work will keep the A40 Westway and surrounding road network running safely and reliably in the future.
What we're doing
Given the scale of the structure, and that some sections are a higher priority than others, we plan to do the work in phases:
- Phase 1 - replace the operationally critical roller shutter expansion joint
- Phase 2 - replace 10 tooth/comb joints, protect parapets at high risk locations and make targeted resurfacing and concrete repairs
We have appointed the contractor Costain to develop the design and construction plans for the project.
Phase 1 progress:
We will replace a large metal roller shutter-type expansion joint (4 metres wide) which runs across all lanes of the A40 within section 4 (see the map above) near Acklam Road. Supporting concrete will be carefully removed using a low-vibration method called hydro demolition, where a high-pressure water jet breaks down the concrete. This is far quieter than traditional methods of concrete removal.
The concept design for this phase was finished in March 2021. We plan to complete detailed design in September 2021 and be on site later in autumn 2021 to start replacing the roller shutter joint.
We currently expect the works to take around nine months.
Outline proposals for how construction and traffic will be managed have been made and will be developed in more detail with our partners and stakeholders.
Current traffic management proposals involve closing lanes on the Westway 24/7 while we replace the expansion joint. At least two traffic lanes will be available during the weekdays in each direction for traffic. The carriageway will be closed overnight and on weekends, in one direction at a time, to help us do the work safely and efficiently.
Traffic diversions will be signposted when the A40 Westway is fully closed in one direction.
Phase 2 progress:
The 10 joints are mainly large expansion joints spanning the gaps between the concrete structures. These enable the bridges to safely expand and move under weather conditions and traffic loading.
We aim to finish the concept design for this phase in November 2021, subject to access for investigations. This will include proposals for managing construction and traffic.
Subject to funding we plan to start the detailed design for this phase in 2021 and complete it in 2022.
If we get the necessary funding for construction, we could be on track for other major joint replacement and maintenance works to start on site in 2022.
Lane restrictions and some partial closures of the A40 at night and on some weekends will be needed to help us do the work safely and efficiently.
Check back here for details of proposed closures/restrictions and diversion routes.
Speed limit restriction
The speed limit was reduced in July 2020 from 40mph to 30mph along the entire stretch of the Westway between the A40 Northern roundabout to the west and Marylebone flyover to the east.
Slowing the speed helps protect and extend the life of the ageing expansion joints in the road until they can be replaced. This makes it less likely we'll have to close parts of the Westway for unplanned works.
Along with Costain, we will work with interested parties to plan access and agree how to offset the temporary impact of the construction works.
Key elements of the work mean we will need to:
- Replace one roller-shutter expansion joint on the A40 over Acklam Road
- Replace 10 tooth/comb expansion joints along the A40 Westway and at Marylebone flyover
- Resurface and waterproof the carriageway where expansion joints are replaced
- Repair concrete in areas under the Westway
- Investigate drainage
- Replace the metal work on inspection access hatches in the carriageway
We have assessed the integrity of safety barriers to protect parapets at high risk places (for example, over live railways). The current arrangement is satisfactory and no other work is needed on those elements.
What we've done
We appointed Costain to move ahead with the next stage of this project after a competitive tender and selection process between March and June 2020.
Costain started design and planning work in July 2020 for a scheme to replace the major expansion joints, including one roller shutter and 10 tooth/comb joints along the Westway and Marylebone flyover, and to develop the proposals for the other high priority concrete repair, surfacing and safety barriers work where needed along the Westway.
After our March 2018 report on the investigations and options for maintaining and refurbishing the Westway and Marylebone flyover structures, a decision was made to go ahead with the project. Financial constraints at the time meant this was put on hold, but in December 2019 we decided to move forward with design and construction plans for the project.
Between 2015 and 2017 we inspected and surveyed all residential and business premises beneath the Westway to help us understand its condition.
We also surveyed different parts of the Westway elevated structures and Marylebone flyover, including the drainage, waterproofing, expansion joints, surfacing, structural concrete and parapets.
We investigated the road surface on the Westway and Marylebone flyover by digging trial holes, taking core samples and surveying the drainage system.