The accident happened outside the St John ambulance station about 9.15am.
Emergency services arriving at the scene found the 38-year-old Dunedin man unconscious behind the wheel but with no other injuries from the crash, a St John spokeswoman said.
He regained consciousness at the scene, but was taken by ambulance to Dunedin Hospital for further checks, she said.
Although the crash occurred outside the St John station, an ambulance based in Mosgiel was sent to the scene.
That was because two other ambulances based at the York Pl station were already out on jobs, she said.
A witness at the scene said it took the ambulance from Mosgiel about 20 minutes to arrive.
Three people were taken to Timaru Hospital by ambulance following a two-car crash near Lake Tekapo about 2pm on Saturday afternoon.
One of the injured received serious injuries in the accident, while the two others had moderate injuries, a St John spokesman said.
