Work to upgrade the northern section of the M25 is continuing this month, with more overnight road closures planned.

The Highways Agency is carrying out £188million improvements to transform the motorway between junction 23 (South Mimms) and junction 27 (M11) into a “smart motorway”.

This involves converting the hard shoulder into a traffic lane, with electronic signs on roadside and overhead gantries providing information that the agency hopes will smooth traffic flows and improve journey reliability.

Gantries are now being built between junction 25 (A10) and junction 27.

Work will take place overnight from 10pm to 5.30am between Mondays and Thursdays, 11pm to 6am on Fridays, and 10pm to 6am on Saturdays. No work is planned for Sunday nights.

The next overnight closures will take place on the clockwise carriageway between Monday, March 17 and Thursday, March 20. This is to allow installation of a gantry across the entire width of the highway. A divertion covering the A10, A406 and M11 will be in place.

When the gantry is lifted into place, traffic will temporarily be stopped on the anti-clockwise carriageway using a rolling roadblock.

John Martin, senior project manager at the Highways Agency said: “We will be installing overhead gantries, some of which span the entire motorway, which will provide drivers with traffic information which will improve journey reliability and reduce the likelihood of ‘stop-start’ traffic flow.

“We have planned the work to take place overnight, when traffic flows are lowest, with a closure in one direction only in order to minimise disruption. Where the M25 is closed in one direction, drivers will be able to continue their journeys by following a clearly signed diversion route.”

Here’s a video showing how a gantry was installed at junction 24 (Potters Bar) last year: Last summer, gantries were installed on the M25 between junctions 23 and 25. You can view an earlier installation of a superspan gantry at junction 24 on YouTube: