The driver of a white van caused havoc by going the wrong way along a dual carriageway, hitting one car and forcing four more off the road.
The rogue vehicle headed east along the westbound A27 near the Brighton turn-off just before 7pm on Saturday.
An ambulance crew treated drivers for cuts and bruises. There was only minor damage to cars.
Members of the public phoned the police but the van had sped off by the time they arrived.
Officers believe it turned towards Falmer and Brighton University and are appealing for witnesses.
A spokesman said: "We are trying to piece together exactly what happened and it's very lucky that no one was seriously hurt.
"We received a number of calls and would like to hear from anyone who has more information."
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