Highways engineers are making good progress on upgrading the M25 motorway past Potters Bar, and now hope to open it fully to traffic in the spring.

The construction phase to convert the section between Junctions 23 (South Mimms) and 27 (A10 Cheshunt), into a “smart motorway”, with an extra lane and traffic management technology, is nearly finished, allowing the Highways Agency to start testing it early in the new year.

Senior project manager John Martin said: “Thanks to good weather and efficiency savings we are some 12 months ahead of schedule on the southern section [Junctions 5 – 7].

“We expect main construction work on that section to be completed in early 2014, followed by a period of testing and commissioning the technology before final completion with road users benefitting from improved journey reliability and reduced congestion from spring 2014.

“The first phase of the northern section is on schedule to be complete at the same time.

“I would like to thank road users for their continuing cooperation during the construction work to improve the M25 and ask for further cooperation during the remaining work, once construction ends.”

The agency says other “smart” motorways, with the hard shoulder converted to an extra lane, and speed limits adjusted to traffic levels, has been very successful, with accidents down by more than half, and reduced congestion.

When the Potters Bar section is complete, the Highways Agency will extend the smart motorway eastwards to Junction 25 (Epping).