Up to one in 10 drivers risk being fined for ignoring lane closed signs on motorways, new figures suggest.
National Highways said the proportion of drivers who comply with the red X signs is “more than 90%”, indicating nearly 10% do not.
Since September 2022, all police forces have been able to use enforcement cameras to prosecute motorists who illegally pass under a red X or enter a lane beyond one.
This can result in a fine of up to £100 and three penalty points, or more severe penalties and a court appearance in some cases.
New figures show it has issued 9,427 Notices of Intended Prosecution since then.
Some 4,926 recipients completed a safety awareness course, with others selecting alternative options such as paying a fixed penalty or having the matter heard at court.
The roads policing unit covering Bedfordshire, Cambridgeshire and Hertfordshire said nearly 300 vehicles were seen contravening a red X displayed on the M25 near Junction 20 on a single day in December 2018 while emergency roadworks were carried out following a crash.
One of the offending drivers contested the matter at court, where he was ordered to pay a fine and costs amounting to almost £1,000.
He also received three penalty points.
Adherence to red X signs is critical to smart motorway safety.
National Highways’ staff switch on the closed lane signs when stopped vehicles are detected in live lanes to prevent them being hit from behind and to help and protect the emergency services.
Chief Constable Jo Shiner, the National Police Chiefs’ Council lead for roads policing, said: “Red X signals are in place on the motorway for your safety and the safety of others.
“Sadly, there are too many instances where motorists fail to comply with a red X signal and put others in incredible danger by driving in a closed lane.
“This is unacceptable and drivers who do so need to understand they face prosecution.”
National Highways traffic officer Dave Harford said: “We don’t take the decision to close lanes lightly, but when we do, drivers must obey the closure.
“A red X signal is there for the safety of everyone on the road – including people in difficulty, traffic officers, recovery and emergency services helping them, and all other road users besides.”
AA president Edmund King said: “As more than a third (38%) of breakdowns on smart motorways happen in live lanes, it is vital that all drivers avoid lanes with a red X as soon as possible, as you never know what danger may lie ahead.”
RAC road safety spokesman Simon Williams described the proportion of drivers using closed lanes as “very worrying”.
He said: “For some time we’ve been concerned that red Xs displayed on signs at the side of the road aren’t nearly as clear as those positioned on gantries directly above each lane.
“We fear this may be a factor in some of the non-compliance.”