Traffic could be using parts of the improved A11 from as early as June.

Highways bosses revealed the latest information as they unveiled safety measures to protect drivers and workers by cutting speed and preventing overtaking on what is one of the region's busiest roads.

Geoff Chatfield, Highways Agency project manager, said contractors were on target to complete the £134m Fiveways to Thetford improvements and dualling project.

'Things are going well on the A11 scheme at the moment,' he said.

'We have done most of the top-soil stripping for the new dual carriageway. A lot of the earthworks are now under way and we are hoping to start building the new carriageways very soon.'

He added: 'We're hoping to construct the first section of new carriageway and have that completed about June time.

'It's a short section down towards the Fiveways roundabout and it's part of the contractors' programme to put traffic on to a section of the new carriageway to enable them to complete the rest of the road.'

The A11 dual-it campaign was launched in August 2008 by Norfolk County Council, working with partners including Suffolk County Council, local MPs, business groups such as Shaping Norfolk's Future and Norfolk Chamber of Commerce, the Gateway A11 East group, Breckland Council and Forest Heath District Council.

More than 16,000 people signed the council's petition to show their support to get the stretch of road from Fiveways to Thetford dualled and a Facebook group dedicated to the cause attracted 3,200 members.

Campaigners had long argued that the dualling of the final stretch was an essential transport link between Norfolk and the rest of the country.

Research by the then East of England Development Agency showed upgrading the road would bring a £600m economic boost to the region.

The news Norfolk and Suffolk had waited for was given by prime minister David Cameron in September 2011, when he confirmed the work on the road.

Contractors, who have faced heavy rainfall, snow and freezing conditions, have so far managed to work round the weather.

Mr Chatfield said said it was important that road-users considered their own, and workers', safety while using the A11.

He added: 'Safety is very important for the Highways Agency. The guys around the site are all in high visibility gear and on the road, we have steel barriers to stop road-users coming off the road.

'We have variable signs on site that encourage people to comply with the speed limits – it's very important.'

Mr Chatfield, who said the signs were working, said one of the biggest problems was caused by people overtaking slow-moving traffic and then colliding with oncoming vehicles.

He added: 'We've had a number of fatalities over the last few years and this scheme, we hope, will reduce that considerably.'

The 9.1 miles of road is due to be completed by December 2014.

matt.gaw@archant.co.uk