Police are asking motorists to avoid the area following a collision on the A27 Shoreham flyover.
The incident took place on the A27 Shoreham By Pass Westbound at A283 Steyning Road (Steyning turn off).
Delays are reported, with tailbacks past the Southwick tunnel, according to police.
One of the three lanes are closed around the Steyning turn off, according to travel reports.
More to follow.