THE A27 at Crossbush, near Arundel, is due to re-open shortly, police said, after a crash between a bike and car earlier this morning (May 13).
Police have been diverting traffic through Lyminster, along the A284, towards the A259, since the collision at 10.20am.
The incident took place on the eastbound carriageway and saw police, paramedics and the air ambulance team in attendance.
The injured motorcyclist suffered serious chest injuries, a police spokesman said.
The force is now appealing for witnesses to the collision to contact them by emailing firstname.lastname@example.org or by calling 101 quoting serial number 399 of 13/5.