Converting the notorious A303 into a dual carriageway from the M3 into Devon is expected to be included in £2bn of road schemes to be announced by the government.

Business leaders want the A30/A303 enlarged all the way, but environmentalists are strongly opposed to the plan.

The A30 is dual carriageway from the M5 to the A303 at Honiton.

But the combination of dual and single carriageway on the A303 from Honiton to the M3 causes horrific jams in the summer as people flock westwards for their holidays.

We are driving ourselves into gridlock

Transport 2000

Conservationists are concerned that widening the road through the Blackdown Hills, a protected area alongside the A30, will destroy its beauty and tranquillity.

One way out of the impasse is to dual the A303 to the A358 junction and then dual that north to Taunton and the M5.

There have been hints in government briefings this will be the preferred option when Transport Secretary Alistair Darling makes an announcement on Tuesday.

But environmental groups like Transport 2000 are very disappointed, and say in the long term any expansion will worsen road congestion.

Business leaders have long campaigned for dualling

Devon Transport 2000 spokesman Martin Goss said: "Dualling another road into Devon is not the right way forward in our view.

"We are driving ourselves into gridlock and the introduction of further traffic to local roads in the long term is not the solution."

Mr Darling is also expected to announce improvements to the railways.

Single stretches of railway could also be 'dualled', including the Exeter to Waterloo line and tracks in the St Austell and Truro areas.