A serious collison has led to the A27 being closed near the Southwick tunnel.
A lorry and car collided on the eastbound carriageway after leaving the tunnel.
The lorry then left the road and ended up on the westbound carriageway.
Two air ambulances attended following the collision.
Both carriageways are closed and will be for some time. Diversions have been set up and motorists are asked to avoid the area.