Drivers are being warned of long delays during the first planned daytime closure of a stretch of the UK’s busiest motorway.
National Highways urged motorists to “only travel if necessary” when it shuts the M25 in both directions between junctions 10 and 11 in Surrey as part of a £317 million improvement project.
The five-mile stretch of carriageway will be closed from 9pm on Friday March 15 until 6am on Monday March 18.
More than 200,000 vehicles are expected to be affected, including many travelling in and out of London, and to and from Heathrow and Gatwick Airports and Channel ports.
Between junctions 9 and 11 the M25 normally carries between 4,000 and 6,000 vehicles in each direction per hour from 10am until 9pm at weekends.
This is the first scheduled daytime all-lanes shutdown on the M25 since it opened in 1986, National Highways said.
The Government-owned company said the action is necessary to enable a bridge to be demolished and a new gantry to be installed.
Four more closures will take place up to September.
No dates have been released for when they will happen, but the next is expected to take place in April.
The project will increase the number of lanes and make it easier to enter and exit the M25 at junction 10, which is one of the UK’s busiest and most dangerous motorway junctions.
National Highways project lead Jonathan Wade said: “Drivers should only use the M25 if their journey is absolutely necessary.
“This is the first of five full closures of one of the busiest junctions on our road network.
“We have spent months planning for these closures and making sure there are diversion routes in place, but there will still be heavy congestion and delays.
“These improvements will bring long-term benefits to drivers who pass through this stretch of the M25, not to mention pedestrians, cyclists and horse riders who will also see positive changes in the area.”
The junction 10 project began in summer 2022 and is expected to last three years.
Steve Gooding, director of motoring research charity the RAC Foundation, said: “For drivers who’ve already had their patience tried by the queues at the junction 10 works, the phrase ‘you ain’t seen nothing yet’ springs to mind.
“National Highways’ plea for people to avoid driving in the area applies not just to trips on the M25 but also to those on surrounding local roads onto which the M25 traffic will be diverted.
“The hope must be that drivers take great care, however frustrating the delays and disruption might be.
“The last thing we need is shunts or crashes, however minor, because the slightest mishap will compound the misery.”