A main road has been closed after a driver crashed into vehicles waiting at traffic lights and then a tree.
The incident took place at about 4.30pm on the A283 in Washington, near Steyning.
The woman, 81, was travelling in a Golf when she struck another Golf waiting at temporary lights near the junction with Water Lane.
The second Golf hit a Mercedes in front.
The driver of the first Golf then spun and hit a tree. She has been taken to the Royal Sussex County Hospital in Brighton. Her condition is unknown but potentially serious.
No-one else is believed to be injured.
Sussex Police urged motorists to avoid the area.
Witnesses should call Sussex Police on 101.