Here’s everything you need to know about when, where and why.

1

Why is the M25 closed?

National Highways shut the stretch of the M25 while a bridge is demolished and a new gantry installed.

It is the first planned daytime closure of the motorway — which encircles London — since it opened in 1986.

Modelling carried out while the plans were being developed estimated drivers would face delays of up to five hours without mitigation measures being implemented — such as urging drivers to stay away and creating diversion routes.

However, National Highways believes only around an hour will be added to journeys because of the steps it has taken, which is based on a reduction in traffic of 50%.

Project lead Jonathan Wade warned drivers against trying to find a quicker and shorter route.

He said satnavs would take them on to smaller roads, making life a misery for people living in the area.

Please don’t travel if you can avoid it

Jonathan Wade

He told the PA news agency: “How many people are going to take the initiative and try and use satnavs?

“There’s probably a greater risk of congestion by people just doing their own thing and thinking they can perhaps beat the signs and find a shorter or quicker route.

“That will cause further congestion on some of the key junctions so please avoid doing that if at all possible.”

He added: “Because it’s so unprecedented, we’ve got nothing to benchmark it against.”

“There’s never been a closure of this nature. We really can’t be certain how many people will heed the messages which we’ve given.

“It’s very difficult to determine right now how effective all our traffic management will be.

“Please don’t travel if you can avoid it.”

When will the M25 be open?

Following its closure at 9pm on Friday, March 15, 2024, the stretch of the M25 will remain inaccessible until 6am on Monday, March 18, 2024.

Concerns have been raised that thousands of drivers will be stuck in gridlocked traffic over the weekend during the unprecedented closure.

But some people don’t have the time to wait for it to reopen — Tom Cruise is planning to use helicopters to fly cast and crew over the closed M25 in a daring bid to film Mission Impossible 8.

Which junctions are affected?

The five-mile stretch of motorway affected by the closure is situated between junctions 10 and 11 in Surrey.

It is closed in both directions.

The M25 normally carries 4,000 to 6,000 vehicles in each direction per hour from 10am until 9pm at weekends between junctions 9 and 11.

Four more daytime closures of the motorway will take place up to September.

The project, which is due to be completed in the summer of 2025, will increase the number of lanes, making it easier to enter and exit the M25 at junction 10 — one of the UK’s busiest and most dangerous motorway junctions.