Fresh calls have been made for a review of the diversion route going to and from Felixstowe through Ipswich when the Orwell Bridge must close, as part of 'Plan B' options for when reduced speed limits are not available.

Highways England in March introduced a £1.5million upgrade to the bridge which enables the speed limit for motorists to be dropped from 60mph to 40mph when high winds of between 45mph and 60mph occur.

Data presented to Thursday night's scrutiny committee at Ipswich Borough Council revealed that measure had prevented three closures of the bridge in May this year alone, which would have totalled 23 hours.

Councillors at the committee, which has lobbied hard for improvements for more than five years, have welcomed the progress, but requested that Highways England and Suffolk County Council return to the committee in the near future to address the outstanding problem of the diversion route for instances when wind speeds mean a bridge closure is still required.

Committee vice-chair Sandra Gage said: "I am pleased with the early results of the use of the lower speed limit on the bridge – it will clearly significantly reduce the frequency that the bridge has to close.

"But there does need to be a Plan B, which is not really the solution we wanted – a northern bypass – but will have to do, and it is about Highways England and Suffolk County Council urgently reviewing the current official diversion route.

"It is wholly unacceptable for this route to be the A1214 through the centre of Ipswich. Roads such as Colchester Road, Chevallier Street, Yarmouth Road and London Road were deemed unsuitable for trunk road traffic over 40 years ago, hence the construction of the current bypass in the early 1980s.

"This route takes traffic along roads with poor air quality areas, which the highways authority is supposed to be addressing.

"Whenever there is an incident on any part of the route, including on the bridge, the role of the bypass is compromised and the traffic diverts through our town, causing gridlock and lost income."

Suffolk Chamber of Commerce estimates that a single bridge closure costs the town's economy £1m per day. It too has echoed calls for a solution when winds are too high for the 40mph limit to be acceptable.

It is not yet clear when the two highways authorities will return to the borough council's scrutiny committee to discuss the issue.