Emergency services are responding to a collision between a motorcyclist and a car in Worthing town centre.
Two ambulances and one police car are in attendance at the Union Place roundabout in High Street.
An eyewitness reported one motorcyclist on the ground being treated by ambulance crews.
High Street has been closed off from the Union Place roundabout down to the junction with Chatsworth Road, causing significant tailbacks.
A Sussex Police spokesman said officers were called to the incident just after 5pm.
The motorcyclist was complaining of pain to their back, said police.
Emergency services are at the scene, and the incident is still ongoing.