Hard shoulder removed from part of M25 in Hertfordshire
The M25 in Hertfordshire has become England's first section of motorway without a permanent hard shoulder, the Highways Agency (HA) has said.
The eight-mile section between junctions 23 for the A1 and junction 25 for the A10 will be available for use by vehicles all day from Monday.
The agency said it would improve traffic flow and capacity.
Motoring organisations the AA and the RAC have been critical of the move, although neither has condemned it.
Hard shoulder running has been trialled on some motorways, including the M42 in the Midlands, but only during periods of congestion.
The agency plans to extend the all-day operation and next month a further 12 miles of hard shoulder will be available for traffic between junctions 5, 6 and 7 of the M25 on the Kent/Surrey border.
Drivers are advised not to stop on the motorway, but to use the emergency refuge areas or leave at the next junction.
Paul Watters, from the AA, said it had "reservations" and removing the hard shoulder was "quite a dramatic step".
"Drivers will not have that feeling of safety on the near-side in case something goes wrong; they will have to wait 2.5km (1.5 miles) for an emergency refuge area and we think that may be stretching it a bit with some vehicles," he said.
"The extra capacity is very welcome; it will solve congestion and reduce journey times but we're not sure it will make the motorway more reliable."
RAC technical director David Bizley said it was "disappointed" the agency had not addressed its concerns over the distance between refuge areas.
Agency chief executive Graham Dalton said the sections were designed to be "at least as safe" as the three-lane motorway they will replace.
"Relatively few breakdowns are things that immobilise a vehicle straight away and in most cases people will be able to get to a refuge area," he said.
"[But if you are unable to], the section is being monitored all the time and traffic officers will be with you in relatively few minutes."
Overhead gantries will display a red 'X' to clear a lane if there is an incident ahead, the agency added.