Good progress has been made on the first full day of the M25’s weekend closure, National Highways has said, but drivers are being urged to stick to the official diversion route in a bid to keep traffic moving smoothly.

The motorway – which is Britain’s busiest – closed in both directions between junctions 9 and 10 in Surrey from 9pm on Friday while concrete beams for a new bridge are installed. It will reopen at 6am on Monday.

Diversion routes take cars on a 19-mile journey on A roads, crossing from Surrey into London’s Ulez area, though National Highways has assured drivers “no enforcement action will be taken”.

M25 closure work
Engineering works taking place at the A3 Wisley interchange at Junction 10 of the M25 as concrete beams for a new bridge are installed (Jordan Pettitt/PA)

However, the highways authority said anyone who ignores official diversion signs in an attempt to find shorter alternative routes will be liable for the £12.50 daily Ulez fee if their vehicle does not meet minimum emissions standards.

Failure to pay the charge when required can result in a £180 fine, reduced to £90 if paid within 14 days.

On Saturday, National Highways said they had seen an increasing number of motorists choosing to ignore the diversion route, starting at junction 8, and instead continuing on the motorway to the next junction.

Simon Elliott, National Highways senior project manager, said it was “important that drivers follow the diversion route in place”.

He said in a statement to the PA news agency: “It is the most effective way for people travelling clockwise along the M25 to reach their destination and will help keep traffic moving as well as possible during this weekend’s closure.

“Coming off at junction 9 means non-freight drivers will end up travelling behind or alongside HGVs which is something we are actively trying to avoid and is likely to have a negative impact on travel times, congestion and the communities they pass through.”

M25 closure
The route is expected to reopen at 6am on Monday (Jordan Pettitt/PA)

The highways authority added that good progress had been made on Saturday, with a number of beams that will form the new bridge having been lifted into place.

The 19-mile diversion route saw an “unusually low volume of traffic”, with residents and local businesses reporting quiet roads and reduced footfall in their towns and villages.

Councillor Rod Ashford from the Reigate and Banstead Borough Council told the PA news agency that, at around 5pm, traffic around junction 8, where the diversion route starts, was “free-flowing with an unusually low volume of traffic”.

M25 closure
A deserted M25 looking eastbound (Jordan Pettitt/PA)

He added: “Given the A217 would be a route to divert M25 traffic to Epsom and around (to the) M25 junction 9, traffic in my area is quiet.”

Meanwhile, in Epsom, a town on the diversion route, workers at Blacks Burgers told the PA news agency there had been a “downturn in business and walk-in trade” compared to last weekend and corresponding with the road closure, whilst the area in general seemed quieter.

National Highways previously urged drivers to only travel the route if necessary, to avoid the closure and to complete their journeys in other ways if possible.

The M25 closure is the second of five planned weekend closures which come as part of a £317 million project to improve junction 10.