The crash took place on the Suffolk and Essex border (Image: Google Maps)
Part of the A12 was shut for more than four hours overnight following a serious crash.
The northbound carriageway was closed between junction 29 for Colchester and junction 30 at Stratford Mary, on the Suffolk border, at about 12.10am on Sunday.
National Highways said a serious collision involving a car and motorcycle had taken place.
A spokesman said the road was expected to be closed for some time.
The carriageway reopened at about 4.20am.
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