Senior Sergeant Craig Brown said a Subaru station wagon and Nissan 4WD were both travelling south about 3.30pm when the Subaru moved to the left to allow other vehicles to pass before it made a right-hand turn into McGrath Rd.
The vehicles collided when the Subaru turned right.
The Nissan rolled four times down a bank.
A passenger in the 4WD, a woman in her late 30s or early 40s sustained a hand injury and was taken to Dunedin Hospital.
Snr Sgt Brown did not know how serious the injury was, but believed she was the only person taken to hospital.
Two children, aged 2 and 4, were also in the vehicle.
The two male occupants of the Subaru, including the 78-year-old driver, were unhurt.