Police are appealing for witnesses to a collision on the A27 near Falmer at 7pm yesterday (Sunday November 25).
A blue Vauxhall Zafira heading eastbound collided with a Highways Agency message board and a stationary lorry which was parked off the carriageway.
The driver, a 48-year-old woman, suffered minor injuries and her passenger, a 79-year-old woman suffered serious but not believed to be life-threatening injuries.
She was taken to the Royal Sussex County Hospital in Brighton to be treated.
Another passenger in the Vauxhall suffered minor injuries and was taken to hospital for precaution.
Anyone who saw what happened is asked to contact police on 101 quoting Operation Nyland or email firstname.lastname@example.org