There was a well-used money machine under the veranda of Colin Clyne Motorcycles on Thames Highway and the footpath was also a busy pedestrian route.
It was very fortunate no-one was injured when a Mitsubishi RVR vehicle swerved across the road and took out the veranda posts, Mr Bolwell said.
"It's lucky it didn't murder a couple of people.
"It could have been nasty," he said.
The 41-year-old male driver, who was from Oamaru, was taken to Oamaru Hospital for treatment.
Police were awaiting results of a blood test and it was believed drugs might have been a factor, Sergeant Wayne Brew said.
The man was travelling north, crossed the road, hit the veranda posts and then crossed back on to the correct side of the road and parked.
A neighbouring business owner heard a bang, saw a vehicle sliding across the road and saw the veranda fall down.
He went to the aid of the driver, who he said was "not at all with it".
He stayed with the man until the ambulance arrived.
A man who lived nearby said he heard an "almighty whack" and, on first inspection, it looked like a truck had overturned.
