Works to fix the A417 ‘missing link’ will start in Autumn 2021, Highways England have confirmed.
The preferred solution to the problem stretch through the Cotswolds was announced in March.
The chosen option for the last stretch of single carriageway on the A417 east of Gloucester, between Brockworth and Cowley, will see a new section of road through Shab Hill.
Highways England have now confirmed construction will begin in late 2021 and will be finished in early 2024.
The road changes will be 3.4miles (5.5km) in length and will cost £435million to build.
The new road will also have a speed limit of 70mph.
Mike Goddard, Highways England Project Manager for the A417 Missing Link scheme, said: “We are hoping to start construction in late 2021 and have the route open for traffic in early 2024, but this is all subject to successful completion of the planning process and funding as part of the Government’s RIS2 announcement.”
The A417 runs between Gloucester, Cirencester and Swindon and is used by many motorists travelling between London and the West Midlands as a shortcut between the M4 and the M5.
The existing road bottlenecks at the Air Balloon roundabout near Birdlip, but after the scheme finishes it will be removed and the Air Balloon pub will be demolished.
In 2014, it was reported there had been 340 casualties on the road in 15 years.
The next step of the project will involve more detailed design work and further public consultation before a formal planning application is submitted.