The woman was driving over the Crown Range towards Queenstown when she lost control of her Ford Capri as the vehicle rounded a corner near the top of the mountain pass.
Constable Peter Reid, of Wanaka, said the open-top vehicle had crossed the centre line, ploughed into a bank on the right-hand side of the road, and overturned.
"The front windscreen struts are all that stopped her from being crushed," Const Reid said.
A motorist stopped and helped the woman from the upside-down convertible, caring for her in the back of a van until ambulance staff arrived.
The ambulance took the woman to the Wanaka Medical Centre.
She was later diagnosed as having a compressed lumbar vertebra, Const Reid said.
Excessive speed and alcohol had both been ruled out as factors in the accident, he said.
"It appears the crash is the cause of driver error," Const Reid said.
