Sergeant Steve Watt, of Queenstown police, said the man, aged in his early 30s, was driving towards Fernhill about 5pm when he drifted left and hit a parked car, shunting it into the back of another parked car.
Both parked vehicles sustained minor damage.
Police described the condition of the driver and his passenger as serious yesterday, but Sgt Watt said the passenger’s injuries turned out to be minor.
He was unable to provide an update on the driver’s condition.
The accident blocked the only route to the Glenorchy-Queenstown road, and to the suburbs of Fernhill and Sunshine Bay, for at least 90 minutes.