Severe traffic delays by up to 45 minutes have been reported in the Chichester and Petworth areas.
Traffic on the A27 eastbound from the Fishbourne to Portfield roundabouts is moving slowly. The A283 southbound from Northchapel to Petworth is also congested.
This is mainly because of the Festival of Speed event at Goodwood, which started yesterday (June 29) and finishes tomorrow.
People are reminded that the event is entrance by ticket only and is fully sold out.