A driver suffered moderate injuries when his car hit a power pole after he had a medical event just north of Waikouaiti.
He was driving in the northbound lane.
Sergeant Tony Woodbridge, of Oamaru, said the man, aged in his 40s, had a medical episode before crashing into the pole in Goodwood yesterday afternoon.
Witnesses driving behind the vehicle said they were terrified the man was going to have a head-on crash with another car.
A police spokeswoman said officers were notified of the crash about 2.20pm.
The driver was later seen out of the vehicle and walking around, she said.
The power pole had been snapped in two.
St John communications adviser Gerard Campbell said the man was taken to Dunedin Hospital by ambulance.