Senior Sergeant Steve Aitken, of Dunedin, said the driver of a northbound car appeared to have misjudged the speed of a vehicle in front of him and crossed the centre line, crashing head-on with a southbound car about 5.30pm, near Pigeon Flat.
The 21-year-old male driver of the southbound car suffered serious fractures to both his legs and a head injury.
He was airlifted to Dunedin Hospital by the Otago Regional Rescue Helicopter.
A female passenger in the other car received a broken ankle and wrist and the male driver had serious injuries. They were both taken to hospital by ambulance.
Snr Sgt Aitken said a truck and trailer unit got stuck near a bridge on Waitati Valley Rd and a heavy haulage unit was used to pull it out.
Another unit slid off Mt Cargill Rd and got stuck. A crane was used to lift it back on to the road.
The road was reopened about 7pm.
Another crash occurred in Dunedin yesterday on Quarry Rd, Kinmont, about 4.50pm.
St John Southern Region communications co-ordinator Alena Lynch said a 30-year-old woman received moderate facial injuries when her car hit a pole.
She was taken to Dunedin Hospital.
