"It got faster and faster. As it went past me I could tell it was in a totally out of control speed.
"I just watched as he went past. I instinctively started to beep my horn but I knew he was out of control so there was no point."
Bartleet said the trailer went "up and out to the side" and the whole unit flipped over on to its side.
"It all happened like a movie with no sound."
The sliding truck snapped a mature tree clean off at its base, bent a steel lighting pole to a right angle and spewed a trail of white plasterboard behind it before coming to a rest on its side and its brakes steaming.
"There was quite a bit of damage. . . there was debris everywhere," Bartleet said.
He was shocked and immediately worried about the safety of anyone in the vicinity and the driver of the vehicle.
Smoke was billowing out of the truck's engine.
Bartleet called emergency services.
Other people in the area were able to get to the truck before him to see if the driver was all right.
He said it was lucky the incident happened so early in the morning as it was a busy intersection. It could have been worse if it was later in the day when more people were around.
Motorists in and out of the city were delayed for much of the day while the truck was removed from the scene.
The intersection has been the scene of other serious crashes.
A similar truck crash happened at the location in April 2015.
At the time, the intersection was reported by the Otago Daily Times as Dunedin's highest risk intersection.
A New Zealand Transport Agency spokeswoman said the Great King St and Pine Hill Rd intersection was being investigated for safety improvements.
"It's on our list."
There were no statistics immediately available on the number of crashes at the intersection.
A police spokeswoman was unable to comment further on the intersection or the cause of the crash as it was under investigation.
Summerland Express Freight was approached for comment but declined to comment further. ODT
