Ravensbourne Volunteer Fire Brigade Chief Fire Officer Ross Bryant said the driver failed to negotiate a slight left-hand bend in the Dunedin-Port Chalmers road in St Leonards about 1am.
The car rolled down a 6m bank and came to rest on its roof on railway tracks.
When firefighters arrived, the man and woman in the car had exited the vehicle and climbed the bank.
The pair, aged in their late teens or early 20s, suffered minor injuries.
The firefighters ‘‘righted'' the car by rolling it on to its wheels and a 4WD towed it down the tracks to a nearby gate to access a road.