One lane on the A27 has been blocked westbound from Fishbourne roundabout following reports of an accident this morning.
According to traffic reports, lane one of two is blocked just after the roundabout heading westbound towards Portsmouth.
The original congestion was reportedly caused by a stalled vehicle on the A27 Fishbourne roundabout after the A259, with police at the scene.
A two-vehicle collision involving a car and a van has subsequently been reported in the outside lane, adding to congestion.
Congestion is now stretching to Stockbridge roundabout on the A27 bypass, with additional queues on the A286 approaching the junction.
Motorists are advised to expect severe delays.