A truck driver who was not wearing his seatbelt was probably distracted or off balance when his dump truck plummeted 180m down a steep bank, killing him, a coroner has ruled.
Bryan James Wilson died at the scene after he was thrown from his cab during the crash on February 9, last year, on Mount Burnett in Kahurangi National Park, in Golden Bay, while he was working for Sollys Transport.
Mr Wilson was driving a dump truck which was carrying a load of oversized rocks that were being taken to a processing plant at the bottom of the hill.
It was his second trip of the day.
Nelson Coroner Carla na Nagara said that while he was travelling down the single unsealed lane, Mr Wilson lost control of the truck on a left hand bend.
"His vehicle continued straight for several metres, before the truck rolled over the embankment and tumbled 180m down the side of Mt Burnett."
Mr Wilson's body was found about 30m from the vehicle's wreckage near the bottom of the gully.
No alcohol or drugs were found in his body and Mr Wilson was not suffering from any medical condition that could have affected his ability to drive or contributed to the crash.
"Mr Wilson was considered competent as a dump truck driver and conscientious worker," Ms na Nagara said.
Constable Greg Taylor of the Tasman District Serious Crash Unit told the coroner the road was "challenging" and required the full concentration of the driver.
He said Mr Wilson took an unusual line around the bend, which led him to get off track and collide with rocks that sent him off the road.
"There was no indication of...braking, not even as the truck went over the bank," Mr Taylor said.
Another Sollys Transport driver, Daniel Duckworth, told the coroner Mr Wilson chose not to wear a seatbelt, and evidence on the day of the crash showed he was not wearing a seatbelt then.
Mr Duckworth said dump trucks had no suspension and if the driver was not wearing a seatbelt and the truck hit a bump, seat springs absorbed the force and the driver would get bounced around, "sometimes even right out of the seat".
Ms na Nagara said it was possible that in driving over rocks, Mr Wilson was jolted or dislodged sufficiently to have lost control of steering the vehicle and/or his ability to brake.
"Mr Wilson's failure to brake further on, when matters were becoming much more serious, suggests to me that rather than failing to react, Mr Wilson was somehow distracted or incapacitated, perhaps off-balance due to not wearing a seatbelt.
"Ultimately, I consider Mr Wilson's death to have been as a result of an accident," she said.