A man was taken to hospital by air ambulance after the blue Ford Fiesta he was driving collided with a lamp post and tree in Crawley Down.
The crash took place in Hophurst Lane at around 3.40am today (Friday March 14).
A spokesman for Sussex Police said the 23-year-old driver suffered serious injuries and was in a critical but stable condition at St George’s Hospital in London.
Hophurst Lane was closed between its junctions with Fermandy Lane and Burleigh Way for more than four hours while emergency services were at the scene.
Police appealed to a taxi driver who may have dropped off the driver in Crawley Down shortly before the collision to come forward.
Sergeant Alan Spicer said: “Anyone who saw what happened or who may have seen the car being driven shortly before the collision is asked to phone Sussex Police on 101 or email email@example.com, quoting Operation Custodian.
“In particular, we would like to hear from a taxi driver who may have dropped off the driver and some of his friends in Crawley Down shortly before this collision occurred. The taxi driver and the injured driver’s friends may have valuable information that could help with our enquiries and we would urge them to come forward.”
Sgt Spicer added: “I would also like to thank anyone whose journeys were affected by the road closure for their patience and understanding.”