Long delays remain around the A27 in Lancing after the road was closed following a serious accident.
A pedestrian suffered critical injuries after being hit by a car on the eastbound carriageway.
It happened 500m east of the Lancing Manor roundabout and led to the A27 being closed to eastbound traffic between the roundabout and the A283 Steyning interchange.
Motorists have been being diverted via the A2025 Grinstead Lane to join the A259 Brighton Road at South Lancing, crossing the River Adur before returning to the A27 via the A283 Old Shoreham Road/Steyning Road.
It has led to heavy congestion, with some drivers saying it's added three or four hours to their journey time
Latest reports suggest there are now half-hour delays for motorists as police continue their investigations.
The Kent, Surrey and Sussex Air Ambulance flew to the scene following the incident just after 6am this morning. The condition of the pedestrian has not been released. There are no reports of any arrest.