Police are appealing for witnesses and relevant dashcam footage following a serious collision near Chichester.
Emergency services attended the scene on the A27 between the Fishbourne and Stockbridge roundabouts after the crash at about 4.10pm on Monday, August 8.
The collision involved a lorry, a black Nissan Qashqai, a red Peugeot van, and a white Chevrolet, which were on the eastbound carriageway.
Officers closed the A27 in both directions while the incident was dealt with, and have thanked the public for their patience.
Three people were taken to the Royal Sussex County Hospital in Brighton with serious but not life-threatening injuries.
One person was taken to St Richards Hospital in Chichester with minor injuries.
Sussex Roads Policing Unit (RPU) officers are investigating the collision and have appealed for anyone who saw what happened to contact them.
In particular, anyone with relevant footage of the incident or of the vehicles in the area beforehand.
Anyone with information is asked to report it to Sussex Police online, via 101, or email: email@example.com and quote serial 1008 of 08/08.