M25 hard shoulder to become traffic lane
The hard shoulder of the M25 in Hertfordshire and Essex is to be permanently converted into an extra lane, the Highways Agency said.
Plans to change the 15 miles of the road between junctions 23 and 27 to add capacity have gone on show in Waltham Abbey.
Variable mandatory speed limits will also be displayed on overhead and verge-mounted signs.
The Highways Agency said overall safety "would not be compromised".
It said as well as adding "much needed additional capacity" between the A1(M) and the M11, the work "will help smooth the flow of traffic and reduce congestion" for the 120,000 motorists who use that stretch of the London orbital motorway each day.
A similar "managed motorway" scheme has already been introduced on other roads, including the M42 in the West Midlands and a section of the M1 in Bedfordshire, where the hard shoulder between junctions 10 and 11 near Luton can be made available to traffic to relieve congestion during peak hours.
However, permanent extra lanes can now be made out of the hard shoulder and work on a scheme on the M25 between Junction 5 in Kent and Junction 7 in Surrey, starts in November.
The extra lane on the stretch between junctions 23 and 27 will also be permanent and work is due to begin in 2013.
The Highways Agency said that should a vehicle break down, extra controls provided, such as additional CCTV and signals, will allow lanes to be closed, traffic slowed down and traffic officers dispatched to the scene.
Project manager John Martin said: "We've used our successful experience of operating managed motorways to produce an updated design.
"This evolution in the design of schemes will provide the additional capacity required, without compromising overall safety."
Exhibitions about the plans are being held at Waltham Abbey Town Hall on 12 and 13 October.
"We will carefully consider all concerns," said Mr Martin.