Police are appealing for witnesses following a collision in Bishopstone near Seaford on Wednesday morning (2 December).
A red Nissan Micra and dark coloured Hyudai Getz collided on the A259 Buckle Bypass at the junction with Marine Parade at about 7.20am.
Emergency services attended the scene. The driver of one of the vehicles, a woman in her 80s, suffered life threatening injuries and was taken by air ambulance to the Royal Sussex County Hospital in Brighton.
Road closures are in place, affecting all lanes, between the junction of A259 with Marine Parade and the junction with Beacon Road. Traffic is currently being diverted via Beacon Road.
Sergeant Kieran McDonald said: “We are appealing to anyone who may have may have witnessed the collision or seen either of the vehicles prior to the incident to come forward.
“We would also like to hear from any drivers with dashcam footage of the collision to get in touch with us.
“If you can help the investigation, ring 101 or email 101 quoting Operation Dollar.