Rocks fell from the hillside above the road about 10.30am today, hitting the nose and side of a vehicle with three occupants, causing airbags to deploy.
Senior Sergeant Clint Wright, of Alexandra, said the people involved were "extremely lucky".
They were getting medical checks.
Snr Sgt Wright thanked members of the public who got to the scene before emergency services arrived, helping to clear the road and keeping traffic flowing smoothly.
Persistent rain today was making driving conditions challenging.
"Conditions are making some of the rocks in the gorges loose," Snr Sgt Wright said.
There was risk of further rockfall and motorists should drive to conditions if travelling on Friday.
A spokeswoman for the the Central Otago District Council advised people to stay at home "especially those in and around the Maniototo area".
