Motorists who saw a car leave the road and roll into a field are being urged to come forward.
The black Ford Focus left the road between the Southeram and Beddingham roundabouts on the A27 near Lewes on Tuesday.
It rolled a couple of times and came to a stop in a field at about 8.50am. The 22-year-old man from Newhaven driving suffered minor injuries.
On the opposite carriageway four vehicles were involved in a collision at 9.05am.
The collision involved a 22-year old man from Billingshurst driving a Silver Vauxhall Corsa, a 21-year old woman from Romford in Essex in an Orange Daewoo Matiz, a 36-year-old man from Haywards Heath driving a black Smart Fortwo and a 40-year old man from Kettering in Northamptonshire driving a white Renault Master.
The woman suffered minor bruising but no-one else was injured.
The road was closed while emergency service dealt with both collisions.
If anyone has any information on the first collision is asked to please email collision.appeal@sussex.pnn.police.uk or call 101 quoting serial 213 of 24/02. Alternatively, you can contact the independent charity Crimestoppers anonymously on 0800 555 111
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