A 23-year-old man from Lincoln is in hospital with serious head and abdominal injuries suffered in a crash near Boston.
The incident happened at around 5.40pm on Punchbowl Lane in Boston on April 15, after a grey Renault Clio left the road and went into a ditch.
The driver of the car, a 23 year-old man from Lincoln, was taken to Queens Medical Centre in Nottingham, suffering from severe head and abdominal injuries.
He is currently in a critical but stable condition, police said.
The front seat passenger was a 20 year-old man from Coningsby, who was taken to Boston Pilgrim Hospital with less serious injuries.
Lincolnshire Police are appealing for anyone who witnessed the collision, or who saw the vehicle prior to the incident, to contact the Collision Witness Hotline on 01522 558855.