The crash, at Kuri Beach, 4km south of Brighton, left the teenager shaken but unhurt.
The driver of the car that clipped his vehicle fared far worse and had to be cut from his car by Fire and Emergency NZ staff.
The teenager’s mother said her son’s vehicle was probably a write-off.
"He was pulling out of a layway and the rider of a motorcycle who saw it said the red car was doing 160-170km when it clipped the front of my son’s car and rolled into the ditch," the woman, who did not wish to be named, said.
"We were driving there yesterday and my husband and I don’t do more than 80km because of the dips and bends there — 100km is too fast there, it should be 80km.
"If my son was an inch more out, we would be talking fatalities."
Firefighters had to cut into the roof to remove the driver, who was freed shortly after 6pm.
A St John spokesman said a man in his 30s was taken to Dunedin Hospital with serious injuries.
