Until now hard-shoulder running has been trialled on some motorways, including the M42 in the Midlands, but only at certain times.
From tomorrow the hard shoulder between junctions 23 and 25 on the M25 in Hertfordshire will be available for use by vehicles at all times.
Then next month the hard shoulder will be available for traffic between junctions 5 and 6/7 of the M25 on the Kent/Surrey border.
The plan is to extend this all-day operation to other motorways.
However representatives from both the AA and the RAC have expressed concerns over safety.