Severe delays are still being reported heading eastbound towards Chichester following a crash close to the A27 Fishbourne Roundabout this morning.
Highways England is reporting approximately six miles of queueing traffic back towards Emsworth.
Sussex Police said one lane of the carriageway has now reopened following a crash between a van and two cars at around 7.20am this morning, Wednesday, October 25.
A police spokesman said there were no reported injuries.
He said police were still on the scene and the damaged vehicles were in the process of being recovered.
Both lanes of the eastbound carriageway were shut for some time to allow emergency services to deal with the incident.
Delays of around an hour have been reported.