The transport secretary Ruth Kelly is to propose allowing drivers on busy motorways to use the hard shoulder in a bid to beat congestion following a successful pilot scheme on the M42.

The proposal to allow traffic to use the lane normally reserved for vehicles experiencing difficulty is seen as a more immediate and cheaper alternative to road-widening.

It will now be introduced over the next two years to the M1, M4, M6, M20 and M25 but the Royal Society for Prevention of Accidents has expressed concerns over a lack of provisions for motorists when their cars break down.

The Highways Agency claims it can change traffic signs in seconds to let drivers know if there is a blockage in a particular lane so they can take alternative action.