At around 9.00pm a silver Ford Focus left the road, collided with a wall and ended up on its roof near Priory Lane.
Police, Ambulances and the Fire Service from both Whitchurch and Overton attended.
The 17-year old driver was taken to Southampton hospital and is in a “serious condition” with head injuries.
Anyone with information can contact Sergeant Lyndon Barrett at Whitchurch Roads Policing Unit on 101 quoting Operation VENUE.
Alternatively call Crimestoppers on 0800 555 111, where information can be left anonymously.
The road is becoming notorious for traffic incidents and there are regular calls for safety improvements.
Thoughts are with the injured and his family and friends, and with the services who deal with these incidents.