The A259 has been blocked westbound at Lancing after a collision between a motorcycle and a car.
Sussex Police said the collision happened at the junction with Chester Avenue, at 8.18am.
Police said initial reports suggested the motorcyclist had suffered a broken ankle.
Police remain on scene as westbound traffic has been partially blocked.
An eyewitness said the motorcycle had been moved off the road and an ambulance was at the scene.
Traffic was reportedly moving past the collision but delays have been reported.