A serious crash at roadworks near Maheno appears to have been caused by a medical event, police say.
Senior Sergeant Anthony Bond, of Dunedin, said officers were called to State Highway 1 between Maheno and Herbert about 3.10pm on Tuesday.
A 61-year-old man appeared to suffer a medical event and failed to slow or stop for roadworks, Snr Sgt Bond said.
The driver drifted into the wrong lane and collided with a rental car containing three people, Snr Sgt Bond said.
The rental car was struck on its left-front side and flipped over.
Members of the public gave first aid and a helicopter was called, which transported the 61-year-old man to Dunedin Hospital, Snr Sgt Bond said.
The highway was closed at Maheno, and a diversion was put in place through Kakanui, until it was reopened about 4.55pm.
A St John spokeswoman said two ambulances, a first-response unit and a manager also responded.
