Sussex Police reopened the A27 near Middle Farm, Firle, at about 5.30pm yesterday (Monday October 8) after a collision.
A driver, who was believed to have suffered a medical episode, was in collision with a car coming in the opposite direction before driving into a ditch. South East Coast Ambulance Service attended along with East Sussex Fire and Rescue Service.
The man was cut from the car and taken to the Royal Sussex County Hospital, Brighton, to be checked over.
He was not injured. The four people in the other car involved were uninjured too.
Motorists were thanked for their patience after the road was closed and diversions were set up.
The collision took place at around 3.45pm.