The A12 was closed off through the morning after a four car pile-up near Chelmsford.
Traffic backed up as far as Colchester as all three lanes of the London-bound carraigeway was shut off until lunchtime as police investigated the accident, which happened close to junction 16 at Galleywood just before 8.30am.
A man was airlifted to Queen's Hospital in Romford after the collision with injuries described as "serious" by police.
One lane closed of the Colchester-bound carriageway was also closed off.
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