A 22-year-old man from Henfield was taken by helicopter to the Royal London Hospital following a collision.
Emergency services were called to Turners Hill Road, East Grinstead, at around 3.50pm on Wednesday (July 2) to reports of a two vehicle collision.
A silver Citroen Saxo was travelling south between the Imberhorne Lane crossroads and Vowels Lane when it collided with a Mercedes Sprinter van which was travelling in the opposite direction.
The 37-year-old man driving the van was uninjured.
Anyone who saw what happened is asked to contact police on 101 or email firstname.lastname@example.org quoting Operation Napier.