An incredible £500million “missing link” upgrade on an A road which promises “smoother” journeys between Swindon and Gloucester is now well underway.

National Highways is backing the scheme to dual a 3.4 mile (5.5km) section of the A417 between the two cities on top of improving connections between two dual carriageway sections at Brockley and Cowley as well as the connection between the M4 and M5.

The Government company charged with improving Britain’s roads said the scheme will preserve the surrounding Cotswolds National Landscape and help to end a “notorious” bottleneck.

It also promises to unlock Gloucestershire’s potential for growth, boost house-building and improve the quality of life for locals, according to National Highways.

Kier Transportation has dug 25 meter deep foundations and poured 360 cubic metres at Shab Hill to prepare for a crossing at Gloucestershire Way.

National Highways A417 project director, Steve Foxley, said: “The A417 Missing Link is a vital scheme for the south west and we have pushed ahead on this much-needed scheme.

“We’re delighted to have made so much progress, so quickly on the scheme and we can’t wait to see customers get the full benefit this vital upgrade.”

Mr Foxley said the upgrade will mean smoother, safer and more reliable journeys for drivers, adding: “We will build on the progress already made to deliver this new stretch of road as soon as we can.”

Piling at Stockwell Lane has begun, installation of a roundabout at Cowley Rab, reducing the speed limit to 40mph, installing CCTV and reduced lane width are among recent developments.

A staggering 428,846 cubic metres of earth have been moved, representing almost half of what needs to be shifted during the construction phase.

National Highways said this week the scheme is targeting more milestones over the summer and autumn, including a new temporary tractor crossing, the start of work on Stockwell overbridge, more drystone walling and the completion of archaeological digs.

A trial is also due to start which will see 200 tonnes of site’s wood chip turned into biochar, a kind of charcoal. National Highways said this will drastically reduce the project’s carbon footprint and contribute to the agency’s net zero targets.

Work on a new dry-stone wall and drainage will get underway at Barrow Wake, with a viewpoint car park remaining closed until March.

Leckhampton Hill will be closing 10 weeks from Monday (August 5) to September 22 for road excavations, drainage and a new entrance to Crickley Hill.

The work will be delivered in three stages, with more details and diversion routes available on National Highways’ website.

On an average day, the stretch of the A417 carries about 40,000 vehicles, with frequent and unpredictable congestion, according to National Highways.

The government company said motorists also divert onto local roads to avoid tailbacks, causing difficulties for neighbouring communities.