Work to improve largest junction on England’s motorway network now complete


02 Dec 2021

The £7.5m upgrade at the junction, which connects the M25 with the A1(M) for Hatfield at South Mimms, sees the widening of the southbound A1 entry slip road to provide a two-lane entry onto the southbound A1 which will ease congestion and improve safety.

Work to improve largest junction on England’s motorway network now complete

Junction 23 on the M25 in Hertfordshire is the single biggest gyratory on the whole of the National Highways network. At about 1.2km in circumference, the junction sees some of the highest traffic flows on the M25.

The upgrade also sees a new footway for pedestrians from the BP service station to the existing footway.

As well as improving safety, the transformation has made the junction safer and easier for drivers and also includes an upgrade of the traffic signal timings to improve flow through the junction.

The improvements at the junction began in August 2019 have successfully reduced congestion and increased capacity at the junction.

A new lane at the Bignells Corner exit from South Mimms services, with a widening of the M25 westbound exit slip road to accommodate an additional lane has made the layout more intuitive as drivers approach the junction. This has created a more free-flowing and safer network in the area around the junction, helping to accommodate local traffic and improving safety for users, including those using the junction to travel to and from the M25 and wider destinations in the UK.

Nicola Bell, National Highway’s regional director in the South East, said:

“I am delighted that this significant junction upgrade is now fully open. These improvements have already added vital extra capacity and improved journey times for road users.

“The upgraded junction will help to tackle congestion and improve safety for the hundreds of thousands of drivers who use this section of the M25 every day. I would like to thank road users in the area for bearing with us while we got the upgrade complete.”

Andy Dean, Connect Plus chief executive, said:

“We are delighted to support National Highways in the successful delivery of the M25 junction improvement scheme at junction 23. The project’s success is a testament to the skills and collaborative working relationship between National Highways, Connect Plus, Connect Plus Services, Jackson and our supply chain.

“To complete works amidst a global pandemic has presented a number of challenges which our teams have tackled with great determination. We cannot thank them enough for all that’s been accomplished and for the positive impact their efforts will bring to our customers using the strategic road network.”

For more information visit the M25 junction 23 scheme page.