Drivers are being advised to car share or use alternative transport

The project on the A38 between Exeter and Plymouth is thought to be the biggest surface recycling scheme ever attempted in the country.

About 70,000 tonnes of material will be taken from the road, then reconstituted and relayed, potentially saving thousands of lorry journeys.

Work on the resurfacing is due to begin in the autumn and will take six months.

'Essential work'

Five miles of the road near Ashburton on the Devon Expressway will be replaced and motorists are being warned they will face major disruption during the work which is expected to take up to six months.

Andrew Hewitt from the Highways Agency said: "It is going to be painful, but this is essential work.

"We have a choice of letting the road crumble and become more and more of a problem and causing delays which are unplanned, or we can carry out the work and do it properly and avoid delays in the future."

Motorists are being urged to stagger their journeys, car share or take the train if possible.