A serious collision where a man has been airlifted to hospital in London has closed the A259 in Newhaven.
Sussex Police said the collision involved a vehicle and the man at about 2.30pm in South Way on the ring road.
The road is closed at the McDonalds roundabout.
Brighton Hove Buses Services 12/12A towards Brighton are being diverted.
Services from Newhaven to Brighton are diverted from Denton Corner via A26 and A27 via Lewes into Brighton.
The road is likely to be closed for several hours.
Police are advising people to avoid the area.
South East Coast Ambulance said it sent three ambulance cars and an ambulance.
The man was treated for serious head injuries at the scene and then flown to hospital by the Sussex Air Ambulance.