A £1.26m scheme to repair one of Southampton's main transport routes is due to begin today.

Work will start on a maintenance programme on the A33 Millbrook flyover scheduled to take six months to complete.

The width of both the east and westbound dual carriageways across the flyover are being narrowed to allow workmen access to repair the flyover's parapets, which means that speed limits have been slashed from 50mph to 30mph.

Trucks and buses will also be banned from using the flyover, with commercial vehicles diverted to the roundabout at the bottom of the structure.

The scheme forms part of a five-year road improvement programme costing £18m which was given the green light by city highways bosses earlier this year.

City chiefs admit that thousands of vehicles heading to the city's boat show in September and into the city centre in the run-up to Christmas could be delayed.

But they insist they will not repeat the mistakes made when bosses took two-and-a-half years to repair the Mountbatten Way flyover, less than two miles away.

Repairs to the Mountbatten Way flyover were finally completed in August last year after causing a nightmare for drivers into the city for 30 months.

City highways boss Rod Anderson said that both lanes of the dual carriageways across the flyover would remain open although their width would be reduced.

He said: "We have worked with our traffic people to check the flows and we do not expect that the work will cause a significant increase in congestion.

"Nevertheless, in the early days as people get used to it traffic will be affected. We would advise people to leave a little bit of extra time for their journey or consider car sharing or another form of transport."

Other roads programmes in the coming months include a scheme to resurface the Western Esplanade, Civic Centre Hill and Havelock Road costing £150,000 and plans to rebuild the carriageway in Bassett Avenue.

A full timetable of the roadworks for this year is as follows:

June to December - maintenance work on Millbrook flyover - cost £1.26m

July 5 to August 27 - Bassett Avenue (Burgess Road to Winchester) - footpath and carriageway reconstruction and installation of new pelican crossings - cost £265,000

August 16-27 - Western Esplanade, Civic Centre Hill and Havelock Road (Central Station bridge to Commercial Road) resurfacing of eastbound and northbound (inbound) carriageway - cost £150,000

September 27 to November 5 - Romsey Road (Redbridge Hill to Rownhams Road) - footway and carriageway reconstruction - cost £137,000.