A woman is in a critical condition after suffering serious injuries in a collision near the Black Horse pub in Great Linford.
Police are appealing for witnesses following the collision.
Around 10.55pm yesterday, a black Ford Galaxy travelling on Wolverton Road, Great Linford, left the carriageway near the Black Horse pub.
A female passenger sustained serious head injuries and was taken to Milton Keynes General Hospital, where she remains in a critical condition.
The male driver sustained minor injuries.
Roads policing officers attend the scene and closed the road while an investigation took place at the scene.
It reopened shortly after 2am today.
Investigating officer PC Ryan Whiles, said: “I would like to speak to anyone who witnessed the collision or anyone who saw the vehicle travelling prior to the collision.
“If you have any information which could assist the investigation, please contact police.”
Anyone with any information about the collision should contact Sgt Mark Scully or PC Andy Martin, from Roads Policing based at Milton Keynes, by calling the 24-hour Thames Valley Police enquiry centre on 101.