Work at junction 23 for M25 and A1 in South Mimms complete

Junction 23 on the M25 in South Mimms is the single biggest gyratory on the whole of the motorway network, measuring at about 1.2km in circumference.

It's an important junction providing links between the M25 and A1 as well as to South Mimms service station.

The improvements at the junction began in August 2019 which National Highways says have successfully reduced congestion and increased capacity in the area.

One of the main changes was widening the southbound A1 entry slip road to provide two lanes onto the major road towards Borehamwood and north London.

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" and "free-flowing" for both motorway and local drivers.

The upgrades have also seen a new footway for pedestrians from the service station to an existing footway, while the traffic signals have been upgraded on the junction to improve traffic flow.

Junction 23 for the M25 where it meets the A1. Credit: National Highways

Nicola Bell, National Highway’s south east regional director, 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."