Drivers using the A14 over the Orwell Bridge face three months of lane closures and 50mph speed limits as cameras and signs are introduced to make the road safer.

Work is due to start next month, and officials from Highways England – the new body responsible for trunk roads in the country – is confident there will be no repeat of the over-running repair work on the A12 near Capel St Mary earlier this year.

A new 60mph limit backed up with average speed cameras and electronic signs warning of dangers ahead is to be installed over the bridge between the Wherstead junction and the Nacton junction.

While the signs and cameras are being installed there will be a temporary 50mph limit from Seven Hills (the junction with the northbound A12 to Copdock Mill (the junction with the southbound A12).

The temporary speed limit will be in force 24 hours a day and overnight one lane in each direction is likely to be closed to allow engineers to work on the road.

Aran Nugent from Highways England said experience in other places suggested the work being undertaken could cut the number of accidents on the bridge by 40%.

Every time an accident closes the bridge there is traffic chaos on the streets of Ipswich and in nearby communities.

Mr Nugent said: “We have seen in some places that this kind of work reduces the number of accidents by even more than that – it is certainly something we will be monitoring closely over the next year or so.”

There had been calls for improvements to the slip road on to the A14 from the fuel station on the Nacton side of the bridge – and there had been suggestions that lorries should be banned from overtaking on the bridge.

Mr Nugent said: “We don’t think those suggestions are really practical for a number of reasons, but they are also issues that we shall be keeping a close eye on.”

He accepted that the work on the A12 between Copdock Mill and the Essex border earlier this year had caused great frustration for motorists as it over-ran by three months.

There have been similar, or even longer, over-runs on the A12 near Brentwood and on the A14 near Cambridge.

Mr Nugent added: “We have looked very hard at what went wrong in those cases and we have built in contingencies for this work on the Orwell Bridge. We will be working very hard to ensure it does not over-run.”

Highways England hopes the work on the bridge will be finished and that the cameras will be working before Christmas.

Ipswich MP Ben Gummer has been campaigning with his parliamentary colleagues and Police and Crime Commissioner Tim Passmore for safety work to be undertaken on the bridge to minimise the disruption in town from accidents.

He hoped the work would be completed on schedule, and that it would seriously reduce the disruption faced by his constituents when the bridge is closed. He added: “Highways England have not delivered (roadworks) as reliably as we would have hoped in the past and I hope and expect that on this occasion it will be completed when they say.”

An exhibition of the proposals at Sproughton Tithe Barn opened just two hours after rush-hour traffic on the bridge was brought to a standstill after a three-car shunt on the eastbound carriageway.

No one was hurt but there were delays until the vehicles were removed from the road.