One of Norfolk's busiest roads is to be partially closed next month to allow a major upgrade of overhead electricity wires.

Traffic using the A47 southern bypass will be restricted to a single lane contraflow between July 11 and August 5 while engineers replace conductor wires on the overhead power lines.

The contraflow will be in operation on the eastbound carriageway between the A11 and A140 while the westbound carriageway is closed, while the work is being carried out by the National Grid

Hundreds of vehicles use the road everyday including cars coming into Norwich, as well as freight vehicles travelling across Norfolk from Great Yarmouth and beyond and the move has sparked fears that it could damage the county's tourist industry as it enters its busiest period as well as see more gridlock in Norwich as cars try to avoid any delays.

Graham Plant, Norfolk County Council's cabinet member for planning and transportation, said he had asked if electronic signs could be put in place alerting motorists to potential delays, while the county council had also agreed to delay resurfacing work on Norwic's outer ringroad due to take place at the same time in a bid to minimise disruption.

'I was concerned about it as this is a major road and this is the middle of the tourist season, but my officers have assured me that this is one of the quietist periods because it's the holiday period,' he said.

Bert Bremner, Norwich City Council's cabinet member for transport and environment, said it would have better to have more notice of the plans.

'There are serious concerns about the effect on Norfolk's trading because of the holiday businesses,' he said. 'We want to make sure that Norwich, Great Yarmouth and the Broads is still open for business and I am very concerned about that and also concerned about the traffic coming into the city. It's going to make the electricity supply more secure, but we could have done with a bit more time.'

National Grid started work in April on an eight-month project to rewire the 52-mile (high-voltage line, running between Norwich and Walpole, near Wisbech. Engineers are renewing the conductors (wires) and fittings and carrying out strengthening work on some of the 224 pylons that carry the wires.

And the works are part of a series of upgrades across the county.

The 400,000 volt power line was built in the early 1960s and now needs refurbishing. The work will enable National Grid to increase the capacity of the line and the network in East Anglia to secure future energy supplies. The project is being carried out by National Grid, leading an electricity alliance with Balfour Beatty.

Other roads to close are in the coming weeks are:

Burnthouse Lane (between Hethersett and Little Melton) will be closed from 23 June to 16 July. A signed diversion route will be in place via: Burnthouse Lane, Little Melton Road, Henstead Road, Queens Road, B1172 Norwich Road.

Intwood Road, south of Cringleford, will be closed from 11 July to 5 August and from 15 August to 6 September. A signed diversion route will be in place via: Low Road, B1113 Main Road and Intwood Road.

National Grid project manager Simon Chandler said: 'We apologise for any inconvenience caused by our work. This is an essential project that will help to ensure that our electricity supply continues to serve us safely, reliably and efficiently for decades to come, securing our energy supply for future generations.

'The safety of the public and our workforce is our top priority. The pylons and wires are very close to the westbound side of the A47 and our working area encroaches on to the road. To carry out this work safely we will need to close the westbound carriageway and operate a contraflow on the eastbound side. Every effort will be made to complete this work as quickly as possible.'