Orwell Bridge new speed limits during high winds
We're carrying out upgrades to the Orwell Bridge in Ipswich. We are installing new electronic signs showing changeable speed limits so that traffic can travel over the bridge at lower speeds safely even during high winds, meaning that we keep the bridge open more often during storms.
The new electronic signs will display a maximum driver speed limit of 60mph for winds speeds of up to 45mph, or a 40mph driver speed limit if wind speeds of between 45mph to 60mph are forecast. The bridge will be closed if wind speeds of 60mph or above predicted due to the safety risk to motorists.
Speed cameras were also installed on the bridge to enforce the maximum speed limits displayed on the electronic speed signs. Orwell Bridge will be able to remain open to drivers more often during storms, and that will mean less congestion in town due to bridge closures.
We only close the bridge for safety reasons when it is essential, and for as short a time as possible. However, we recognise that closing the bridge causes disruption to the town.
A year-long study was made on the aerodynamic properties of the Orwell Bridge, to identify potential steps that we can take to keep the Orwell Bridge open to traffic during high winds. The report was carried out on our behalf by City University of London and they used the latest computer technology designed to test vehicle stability specifically on the Orwell Bridge. The bridge was split into 15 million ‘cells’ for the study and 36,000 tests were run. They assessed the accident risks for different types of vehicles and wind directions.
The aerodynamic study concluded that the current wind limit of 60mph for closing the bridge is correct for safety, but that reducing the traffic speed limit down from 60mph during high winds means that the bridge can remain safely open when the wind is at certain speeds.
The findings were theoretical and needed to be validated using a wind tunnel. Wind tunnel testing was carried out during 2020. These tests mean that we now understand better how winds of different speeds and directions can affect the safety of traffic on the bridge. You can read about the study.
A road safety audit was also carried out to confirm that the new signs do not pose any safety issues.
Safety is our number one priority. Like other high bridges around the country, the safety of road users on Orwell Bridge can be affected by high winds. The bridge is closed to all traffic if there are gusts of wind of 50mph or more in certain directions, or gusts of 60mph or higher, regardless of wind direction. This is in line with best practice, and is based on studies of lorries overturning in strong winds.
Decisions to close the bridge are based on Met Office forecasts. This allows us to inform road users in advance of any potential closures, and reduce the impact of traffic on the diversion route through Ipswich.
In recent years we had already made some changes so that closures can be both implemented and removed within a 20-minute period, and we had introduced a new protocol for making and communicating decisions about the bridge closures to give road users more time to make decisions about their journeys.
We’ve later commissioned new ground-breaking studies which show that we can let traffic use the bridge even during certain strong wind speeds if the speed limit is reduced.
We have now completed our work to install the new signs that allow the speed limits to be changed according to the wind speed.