A crash led to the closure of the A23 at the junction with the A27 on the edge of Brighton an hour before the start of the evening rush hour.
No one was injured in the crash which the Highways Agency said involved three vehicles and the police said involved two cars.
The southbound side of the A23 was shut while the road was cleared and made safe. Queues were reported to stretch seven miles back to Sayers Common as the rush hour got under way.
Sussex Police said: “Police were called to the intersection of the A23 and the A27 north of Brighton shortly before 4pm on Monday (21 March) where two cars had collided on the southbound approach to the roundabout.
“No injuries were reported but the crash led to the southbound A23 being closed until the scene could be cleared.”
