Mosgiel man Matthew Bernard O'Neill said he was stopped at the pedestrian crossing in South Rd, near the Caversham shops, about 4.30pm, when a van behind him failed to stop and smashed into the back of his car, rolling his hatchback.
''I wasn't expecting anything and I've just been turned around and flipped over.''
The car came to rest on its roof on the kerb, but he escaped injury.
The 39-year-old was unable to open his driver's side door, but a passing Good Samaritan, Dunedin woman Rochelle Kane, managed to do so and helped him from the vehicle.
A shaken Ms Kane explained she was simply doing what her father Noel, a volunteer firefighter with the Ravensbourne brigade for 45 years, had always instructed her to do.
''I just ran over to make sure he's OK.''
A witness said the man driving the silver work van had a young boy as a passenger in the front seat, and tried to take evasive action before slamming into the back of the stopped red hatchback.
St John spokesman Gerard Campbell said one person with minor injuries was taken to Dunedin Hospital.
The ambulance service now has a policy of no longer supplying the ages of those treated.
Police attended and interviewed those at the scene, and the road was reduced to one lane for a time.
