The truck crashed through a fence as it was descending Galilee Lane before coming to a much-needed stop on a private driveway.
The vehicle was prevented from falling any further when it struck a parked campervan.
Had it not, it could have careered over the edge and down 200m to the bottom, potentially striking houses along the way down.
Sumner Volunteer Fire Brigade chief fire officer Daryl Sayer said the driver was "extremely lucky".
The brigade attended the incident.
"It was pretty concerning.
"If it hadn’t come to a stop as it did, it would have fallen much further."
Sayer said the driver was taken to hospital with moderate injuries.
Police were investigating.
The brigade posted the photos of the incident to its Facebook page, blurring out the name of the transport company.