A 17 year old was flown to hospital overnight after a crash on the A303 which closed the road in both directions for much of the night.
It happened near the Countess Roundabout, on the stretch heading towards Stonehenge.
A Wiltshire police spokesperson said: "At approximately 10.30pm yesterday (12/05), we were called to a collision between a Mercedes Sprinter van and a 17-year-old male pedestrian on the eastbound carriageway.
"The male, who is from the local area, was taken by air ambulance to Southampton General hospital with head and leg injuries.
"The male driver of the van was shaken but uninjured.
"The road was closed for approximately six hours."
PC Charlotte Sartin, from Wiltshire Police's Collision Investigation Unit, added: "We would like to speak to anyone who may have heard or seen this collision yesterday evening.
"The van was travelling on the eastbound carriageway of the A303 when the collision happened; were you in the area at the time? Perhaps you have dash-cam footage?
"If you can help, please contact the Collision Investigation Unit on 101 quoting reference number 54200044812."