THE M25 will close for a full weekend this month to allow for further roadworks and the construction of a new bridge.
Motorists are being warned to expect delays after a third weekend closure of part of the motorway was announced.
The busy motorway between junctions 10 and 11 will be closed from 9pm Friday July 12 to 6am Monday July 15, said National Highways.
It will be shut for the construction and installation of a new bridge on the western gyratory of the roundabout at Junction 10.
National Highways say it will be installed as part of ongoing work to make journeys safer and reduce pollution.
The new bridge consists of 68 beams, each weighing 16 tonnes, and another four beams weighing 40 tonnes.
This month's closure will be the third of five weekend closures of the motorway - which encircles London - as part of a £317 million project to improve Junction 10.
Motorway vehicles will be directed along a diversion route on A-roads.
Among the people affected will be many of those travelling to, from and between the UK's two busiest airports, Heathrow and Gatwick.
There were fears of severe congestion on diversion routes ahead of the first two closures in March and May, but many drivers followed advice to avoid the area, meaning long hold-ups were avoided.
National Highways and delivery partner Balfour Beatty Atkins are working with emergency services, Surrey County Council, local businesses and Gatwick and Heathrow Airports to ensure that disruption is kept to a minimum.
Jonathan Wade, National Highways Senior Project Manager, said: "The previous two closures have gone well with significant progress being made during both.
"We would urge all drivers to follow the official diversion route as this is the best chance of reaching your destination in good time.
"Please ignore your satnavs and follow our diversion route instead."
Local residents, holidaymakers, concertgoers and sports fans should plan their journeys in advance and make sure they allow extra time or make alternative travel arrangements.
National Highways said their overnight closures usually start from 10pm and finish by 5.30am Monday to Thursday and from 11pm Friday to finish by 6am on Saturday.
But they warned this could change depending on the volume of traffic and when they can close the road safely.
Full diversion route details
The full details on all diversion routes are below.
Junction 10 - Junction 11: exit the M25 at J10 and take the 3rd exit to the north bound A3 to the A245 Painshill Junction, A245 towards Woking, and Byfleet.
Then at the Six Crossroads Roundabout take the 5th exit to the A320 continuing to M25 Junction 11 where the diversion will end.
Junction 11 - Junction 10: exit the M25 at J11 and take the 3rd exit to the A320 south towards Woking, then at the Six Crossroads Roundabout take the A245 towards Byfleet.
Continue on the A245 to the A3 Painshill junction, then take the 3rd exit to the southbound A3 to Junction 10 where the diversion will end.
Avoiding the closure by taking the M25 via the Dartford Crossing may also be quicker, said National Highways.
The March closure was the first planned daytime shutdown of the M25 since it opened in 1986.
The project, due to be completed in summer 2025, will increase the number of lanes at Junction 10, which is one of the UK's busiest and most dangerous motorway junctions.
Between 4,000 and 6,000 vehicles normally use the M25 between Junctions 9 and 11 in each direction every hour from 10am until 9pm at weekends.
The final two weekend closures as part of the project will take place later this year.
Planned M25 closures in 2024 and beyond
2024's first closures took place on March 15, between junctions 10 and 11 in Surrey on the UK's largest motorway.
They lasted over the weekend with the road only reopening on Monday March 17.
The second set of closures took place during a weekend in mid-May, with junctions nine and 10 shutting both ways.
Now the M25 is set to close for the third time this year, as National Highways said it will shut the motorway between Junctions 10 and 11 in Surrey from 9pm on Friday July 12 to 6am on Monday July 15.
This will be the third of five weekend closures of the motorway - which encircles London - as part of a £317 million project to improve Junction 10.