An overturned car and trailer on the A27 between Worthing and Arundel is causing delays, police have confirmed.
Sussex Police said officers were called to the incident at Hammerpot, near the A280 roundabout outside Angmering, at 10.10am, reporting that it had caused a fire and the road to be blocked.
No-one has been injured in the incident, according to police.
Reports on social media suggested the traffic is backed up as far as the Offington roundabout.
West Sussex Fire and Rescue Service has been contacted for comment.