M4 Bridges - Junction 3 to 12

Cleveland Bridge was chosen to fabricate and install 12 bridges in just nine months as part of Highways England's major M4 upgrade.

  • Year: 2020
  • Location: M4, England
  • Client: Balfour Beatty VINCI Joint Venture
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The M4 is the main strategic route between London, the West of England and Wales, carrying on average 130,000 vehicles per day.
Highways England is improving the stretch between junction 3 at Hayes and junction 12 at Theale by upgrading it to a smart motorway.
This will provide much-needed extra capacity by creating an additional lane for traffic, with enhanced technology to smooth traffic flows and manage incidents. Much of the M4 was originally built as a two-lane dual carriageway and has been upgraded several times over the years. The upgrade to a smart motorway means that 11 bridges needed to be replaced to make room for the extra lane. In addition, the bridge that carries the M4 over the River Thames at Bray needed to be widened to support the new smart motorway.


Cleveland Bridge was appointed by Balfour Beatty VINCI Joint Venture to supply, fabricate and install all 12 bridges along the upgraded stretch of motorway, along with various temporary works required to enable bridge installation. As well as working to supplied bridge designs, Cleveland Bridge enhanced value engineering by designing and fabricating the temporary rocker bearings for the integral structures, as well as the temporary bridge restraint systems for the installations.

Cleveland Bridge also fabricated a unique steel training bridge to be used on the M4 project site. The 18-metre model footbridge is the first of its type and size in the UK, and will allow apprentices, technicians or graduates to learn and apply the skills involved in the tendering, planning and construction of a bridge.


One of the greatest challenges of this project was the compressed programme. The first bridge at Monkey Island had to be completed by November 2019. The next six had
to be installed during an eight-week window between April and June 2020, followed by the final five bridges by mid-August 2020. Cleveland Bridge worked in close collaboration with all project partners to meet these project deadlines and fulfil the challenging programme targets.

Access into many of the bridge sites was restricted, with limited space for temporary bridge assembly works. Precise planning and careful project management of all follow-on trades was essential to ensure smooth, safe operation in the limited space available. Cleveland Bridge worked closely with concrete formwork subcontractors to coordinate the parapet formwork installation once the steel girders were assembled, as well as with Balfour Beatty VINCI Joint Venture to organise site access and assembly works alongside other site operations, such as piling and groundworks. All parties held weekly progress and coordination meetings to ensure all aspects of work were safely coordinated and controlled.


The entire scheme was focused along one of the UK’s busiest sections of motorway, close to the M25 and Heathrow Airport. This meant every effort had to be made to minimise disruptions and delays for road users.
Wherever possible, deliveries to site were made at night during either lane closures or, where necessary, full road closures.
There were challenges in the fabrication of some bridge components too. The deep haunch girders required for Thames Bray were up to six metres high, which meant manoeuvring them around the production centre required extreme care and precision.


Monkey Island (Nov 2019) – a multi-span bridge carrying Monkey Island Lane over the M4 near the village of Bray. The bridge weighs 397 tonnes and measures 82 metres in length.

Riding Court Road (April 2020) – 267 tonnes and 45m integral single-span bridge over the M4 connecting the villages of Datchet and Langley, near Slough.

Marsh Lane (April 2020) – a 233-tonne, 46m-long integral single-span bridge near Slough, connecting the villages of Dorney and Lent Rise.

Recreation Ground (May 2020) – 111 tonnes and 44m integral single-span bridge over the M4 connecting the B376 Slough Rd through Upton Court Park near Slough.

Ascot Road (May 2020) – a 260 tonne, 50m integral singlespan bridge, to the east of junction 8 and 9.

Huntercombe Spur (May 2020) – Junction 7 – 362 tonnes and 44m integral single-span bridge leading onto the A4 towards Slough.

Thames Bray (June 2020) – The only structure that is an extension to the M4, it carries the motorway over the River Thames. It spans 105m and weighs 265 tonnes.

Old Slade Lane (July 2020) – A 151 tonne, 50m long integral single span bridge over the M4 carrying Old Slade Lane to the nearby Old Slade Lane sewage works.

Oldway Lane (July 2020) – A 65 tonne, 50m long single span foot/equestrian bridge crossing the M4 between Chippenham, Slough and Dorney Common. This was the only footbridge for Cleveland Bridge on this project.

Wood Lane (July 2020) – A 320 tonne, 90m long two span bridge crossing the M4 carrying Wood Lane from Slough to the existing Wood Lane Sewage Works.

Datchet Road (August 2020) – A 675 tonne, 106m long 3 span bridge carrying Datchet Road over the M4 between Datchet and the district of Upton, Slough. This bridge included the heaviest and longest single lifts on this project with 2 of the paired girders at 63m long and 170 tonne each.

Lake End (August 2020) – A 500 tonne, 80m long 2 span carrying Lake End Road over the M4 between Dorney and the district of Lent Rise, Slough.

To limit local disruption, the majority of bridges were built adjacent to the existing bridges before they were demolished.
All of the bridges were installed on or ahead of programme without any delays, enabling the roads to be reopened slightly early. Thanks to the strict health and safety procedures
implemented by all parties on all sites, there were zero incidents or accidents.

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