A high-tech system that changes speed limits with the aim of improving road safety and helping reduce congestion is to be introduced on the M20 in Kent.
The variable mandatory speed limit scheme will be put in place between junctions 4 and 7 near Maidstone later this month.
The introduction of the system follows a public consultation in 2009.
Traffic sensors calculate optimum speed limits to keep traffic moving and these are displayed on overhead gantries.
The scheme is already being used on the M25 and the M42 and is also being put in place on the M4 in Wales.
Highways Agency regional performance manager Barry Westwood said the controlled motorway system would reduce congestion and make drivers' journeys safer.
He added: "On the M25, where the system has been in place since 1995, it has helped to make the motorway safer by reducing the frequency of collisions by 10% and by encouraging drivers to keep within the speed limits to provide smoother, more reliable journeys during peak times.
"An overall reduction in emissions of between 2% and 8% has been recorded on the M25."
Advisory variable speed limits have been in operation on the M20 since July 2007.