The programme focused on the replacement of seven expansion joints and concrete repairs on the elevated carriageway between Wood Lane and the Marylebone Flyover.

The works, which began in early 2024, covered roughly 2km of the roughly 4.5km stretch of elevated road that carries about 96,000 vehicles a day through the London boroughs of Kensington and Chelsea, Hammersmith and Fulham and the City of Westminster.

Engineers replaced metal tooth‑comb expansion joints – fittings that bridge gaps between concrete sections and allow the structure to expand and contract with temperature changes and traffic loading – on the main carriageway and on slip roads. Costain had previously replaced a critical roller expansion joint on the flyover as part of an earlier package completed in 2022.

Costain completed the complex installation of seven expansion joints

The company said the works also included concrete repairs, resurfacing and other ancillary measures intended to improve the safety and reliability of the route. One particularly challenging replacement ran over the A404 and required live traffic to remain operational while the joint was installed.

To limit disruption, Costain’s engineering team adopted offsite manufacturing and modular methods, trialling joint installations away from the live carriageway and using temporary bridging cover plates to mitigate movement from changing weather while work proceeded. TfL and Costain also sought to minimise road closures and encourage co‑working among local suppliers.

TfL has an ongoing programme of maintenance and renewal for ageing reinforced‑concrete structures across London’s road network. The Westway sections were built more than 50 years ago and periodic replacement of expansion joints and other components is regarded as necessary to prevent unplanned failures and maintain traffic flow on heavily used strategic routes.

Costain is due to begin a further package of work on the A40 Westway and at the Marylebone Flyover in 2026.

Separately, Costain and TfL are also progressing renewal works on the Gallows Corner Flyover, a key link to the M25, as part of wider efforts to improve reliability on the capital’s road network.

Costain senior project manager Emma Curran commented: “The A40 is one of London’s busiest routes and vital to regional prosperity and economic growth. Our upgrades have extended the lifespan of this section of the A40 by more than 50 years, and thanks to our close collaboration with TfL and the application of production-thinking principles, we ensured minimal disruption to residents and road users.

“We’re looking forward to progressing to the next package of works, maintaining our high standards of safety, quality and best-in-class delivery, to further improve the resilience of London’s road network.” 

TfL project manager Charlotte Day said:“The A40 Westway is a critical transport artery into the nation’s capital that has required essential maintenance works. Costain and its supply chain has worked efficiently and innovatively to replace the joints that will ensure the road can continue to run safely and reliably for years to come. This has all been achieved with the least disruption possible to people using the road and living in the area.”

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