Part of the northbound carriageway of the A12 at Lowestoft has been closed off for emergency repairs on a burst water main.
St Peter's Street is closed between Katwijk Way/St Peter's Street roundabout and the Jubilee roundabout.
Traffic is being diverted along the A1144 St Peter's Street, Normanston Drive to Peto Way, Millennium Drive and Bentley Drive on the A1117.
Motorists will re-join the A12 at the Tesco roundabout.
The repairs should be completed by the early hours of tomorrow morning.
For the latest traffic information road users can visit www.highways.gov.uk/traffic, call the Highways Agency Information Line on 0300 123 5000 or listen to Traffic Radio on DAB digital radio or their local radio station.
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