Why does the Orwell Bridge have to close in high winds?
- Credit: Mark Nunn
Over the last five years there have been 12 major closures on the Orwell Bridge as a result of weather disruption - here we look more at the impact this has.
The closures - not including today’s - have led to more than 88 hours without traffic flowing across the iconic bridge which heads out of Ipswich town.
It is generally high winds and cross winds and the danger that causes to traffic that results in Highways England shutting the A14 over the River Orwell.
When was the Orwell Bridge built and why?
Construction of the Orwell Bridge, over the River Orwell, began in October 1979.
Dutch corporation, Stevin Construction B.V were the main contractors for the project and the 1,287 metre long behemoth was completed in 1982.
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The bridge runs from Wherstead to the site of the now defunct Ipswich Airport and was first built to carry the old A45 (now the A14) out of Ipswich.
When does the bridge have to close?
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Highways England have several conditions under which the Orwell Bridge is closed.
Their decision depends on data from the Met Office and readings from Orwell Bridge weather station.
Highways England used to rely solely on the weather station but now takes Met Office data into account.
This allows them to tell motorists earlier that closures are expected.
Closures all depend on wind speeds for fear that strong winds will cause high-sided vehicles to tip over.
The decision is based on wind speeds from certain angles, based on a quadrant diagram.
If there is a 50mph wind hitting traffic head-on, this will not cause the bridge to close but cross-winds at the same speed will.
Fixed road signs are used to close the road, greatly reducing the time it takes to shut and re-open the bridge.
When does the bridge re-open?
Again, Highways England depend on Met Office data and readings from the bridge weather station.
The bridge is deemed safe to re-open when three consecutive wind speed readings on the Orwell Bridge have been below 45mph.
This has been increased from the previous policy of three readings at 30mph.
Can anything be done to change this?
The Orwell Bridge used to only close to high-sided vehicles when wind picked-up but there is no way to police such vehicles and prevent them from crossing the bridge at times.
This led Highways England to change their policy and close the bridge to all vehicles in dangerous weather.
For a number of years Suffolk County Council has been working on a business case for a northern bypass to alleviate all traffic in Ipswich.
Transport secretary Chris Grayling even visited Ipswich in May this year to discuss the plans.
Read the latest bypass updates here.
In October, a nine-month study of the bridge’s aerodynamics was launched to determine future closure measures.