Drivers have been warned to “stay at home” as the unprecedented closure of the M25 is expected to cause a “carmageddon” of gridlock traffic this weekend.
The five-mile stretch of the motorway between Junctions 10 and 11 in Surrey was closed in both directions at 9pm on Friday and will remain shut off until 6am on Monday while a bridge is demolished and a new gantry is installed.
This is the first planned daytime closure of the motorway - which encircles London - since it opened in 1986.
National Highways said modelling carried out while it was developing its plans for this weekend indicated vehicles would face delays of up to five hours without mitigation measures, such as urging drivers to stay away.
Project lead Jonathan Wade said earlier this week: “Please don’t travel if you can avoid it.”
The M25 normally carries between 4,000 and 6,000 vehicles in each direction every hour from 10am until 9pm at weekends between Junctions 9 and 11.
An 11.5-mile diversion route has been created to direct motorway traffic along A roads.