Police are seeking witnesses to a collision on the A22 at Nutley.
The incident happened at 5pm on Wednesday (September 17) after two cars collided on the A22 Horney Common Road near to the Lampool Roundabout. police said.
Police said a Rover 100 being driven by a 30-year old man from Polegate collided with a Mercedes A160 driven by a 49-year old woman from Chiddingly.
The Rover driver was taken by air ambulance to the Royal Sussex County Hospital in Brighton with serious injuries, police said.
The road was closed for nearly four hours while police assisted by highway staff dealt with the scene and began an investigation.
Police are appealing for anyone who may have witnessed the collision.
Sergeant Dan Pitcher from the Sussex Road Policing Unit said: “We are particularly keen to speak with anyone who may have witnessed the driving of a white Seat Leon seen travelling south on the A22 between Nutley and the Lampool Roundabout at the time. Anyone with information is asked to contact us via firstname.lastname@example.org or by calling 101, quoting Operation Ambleside.”