About 42,000 vehicles use the road every day

The plans involve widening the existing A74 at Carlisle into a three-lane motorway and a new separate road in the area known as the Cumberland Gap.

The Highways Agency has received 27 objections to the project.

The inquiry is being hosted at the Solway Business Centre in the Kingston area of Carlisle.

Countryside fear

The five-mile (8.4km) stretch of the A74 is the main route between England and Scotland and carries 42,000 vehicles a day, including about 10,000 heavy goods vehicles.

As well as widening the existing road, other work will involve building a new bridge over the River Esk to carry non-motorway traffic, and replacing the Mossband Viaduct, which carries the A74 over the West Coast Mainline.

Objectors to the scheme are worried about the impact building work will have on surrounding countryside.

A spokesman for the Highways Agency said: "The public inquiry will be held by an independent inspector who will hear the evidence from all parties and then make recommendations to the Secretary of State."