Roadworks on the main road from Suffolk to London could cause problems for drivers for the next 18 months.
National Highways, which is responsible for the country's major roads, is replacing the concrete carriageway at Margaretting, south of Chelmsford.
The £65-million project forms part of a nationwide drive to replace or repair ageing concrete roads across the country.
Work starts on Monday week, February 27, and is not expected to be completed until the summer of 2024.
Decades of use and hundreds of millions of journeys have left the A12 in need of vital upgrades, which will improve safety, create a smoother road surface and reduce noise for those using it.
The scheme will see National Highways completely remove the concrete road surface down to the foundations, before rebuilding the road with recycled material and a new smooth asphalt surface.
As well as resurfacing the road, the project will also see replacement kerbs installed, the drainage system refurbished, safety barriers replaced, new road markings and new reflective road studs – commonly known as ‘cat’s eyes’.
Preparation work has already begun with the installation of speed cameras, CCTV, and temporary barriers.
The existing 40mph speed limit will remain in place for the safety of workers and others using the road.
National Highways expect increased congestion and traffic delays during peak times. Those travelling through the section are asked to plan ahead and allow extra time for their journeys.
Delays through the road works are projected to be a maximum of 10 minutes for those travelling northbound and 15 minutes for those going south.
Karl Brooks, National Highways Programme Delivery Manager, said:
“The A12 is one of the region's most important roads and carries 80,000 vehicles each day helping to connect London with Suffolk.
“We are sorry for the inconvenience this work will cause and are doing all we can to minimise disruption – this includes working overnight and at weekends."
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