A 15-mile section of the M25 is to be widen by using the hard shoulder to provide an extra lane, with work due to start next year.

The affected section is on the southern side of the motorway, between junctions five and seven (Sevenoaks and Redhill/M23 intersection). It is one of the most notorious traffic blackspots on the orbital motorway, which is known for its traffic congestion at peak times.

Using the hard shoulder in this way will make the M25 a ‘managed motorway’, which means that additional lights and signage and speed controls will be installed to allow the hard shoulder to be opened as a running lane during busy times and closed at quiet times to preserve its original function.

Emergency refuge areas are provided every 1.5 miles and CCTV is used to monitor the road, so any breakdowns are quickly cleared. Variable speed limits are often also used to help manage traffic flow, based on the well-proven premise that when traffic is heavy, traffic flows much better if everyone sticks to a lower, more stable speed.

The concept was first trialled in the UK in 2006 on the M42 near Birmingham and is was credited with reducing accidents by more than fifty per cent over a three-year period.  Since then, schemes have also been introduced on the M6, M4  and M5 — all notorious congestion blackspots.

The decision was welcomed by James Hookham of the Freight Transport Association:

“FTA feels that the proposal of what is essentially ‘creating an extra lane on the M25 is good news for this particularly busy stretch of motorway.  Some may see it as the Highways Agency widening on the cheap, but we feel that this will give motorists and most importantly our members extra capacity and will help to keep the motorway moving.”