Driver error was the likely cause of the death of a truck driver near Arthur's Pass in 2011, a coroner has found.
Piki Lewis Jones, 34, of Napier, died on June 22, 2011, after his truck broke through a barrier while descending the Otira Viaduct. It plummeted about 30 metres to the riverbed below.
Coroner Christopher Devonport released his findings today after an inquest in Christchurch in May.
Jones had been driving a fully-laden STL truck west through the Otira Highway about 6am on June 22 when he let another truck pass him just before the viaduct.
Serious crash investigator Senior Constable Simon Burbery told the inquest that soon after Jones passed under the rock shelter below the viaduct his truck crossed the centre-line. It hit steel netting retaining the rock face on the opposite side of the road.
Jones steered the truck back to the left and hit the trailer of the truck that had just passed him. Jones' truck then crashed through the barrier at Starvation Pt and went over the bank, Burbery said.
The front of the truck's cab struck the rocks before toppling onto its roof and the trailer landed on top of the cab.
Jones died at the scene. His body was not able to be retrieved by emergency services until the next day.
An autopsy found Jones had suffered high-energy impact injuries to his head, chest and spine.
He had also had ischaemic heart disease and at some stage had suffered a heart attack.
However, pathologist Dr Martin Sage found no evidence for a recent event that might have caused the accident.
Jones had been self-medicating his chest pain with an angina medicine. He had also smoked cannabis within about three hours of his death.
Although Jones was considered an experienced driver, the day of the accident was likely his first trip east to west over the Otira Gorge, Devonport found.
NZ Transport Agency transport officer Paul Keating and engineering consultant Dr Timothy Stevenson agreed that the brakes had failed, but disagreed over the cause.
Keating gave evidence at the inquest that the brakes might have failed as a result of being out of adjustment.
Stevenson gave evidence that brake fade - where excessive use overheats the brakes - was the likely cause.
If Jones was in the incorrect gear for the steep descent, overuse of the brakes could have led to brake fade.
The truck was too damaged in the crash to determine which gear Jones had been in while descending the viaduct.
Jones' logbook was not accurate at the time of his death, so Devonport was unable to conclude whether fatigue was a factor in the crash.
False entries were found once fuel records, vehicle maintenance records and ferry sailings were compared to his logbook.
In his findings, Devonport said it "may never be known" what caused Jones' truck to suddenly accelerate, leading to the crash.
Fatigue, the effects of cannabis or a medical event could not be ruled out as potential causes, Devonport found.
But the coroner concluded it was "most likely" that lack of experience driving through the Otira Gorge resulted in driver error, with the incorrect gear engaged leading to an over-reliance on the brakes, resulting in brake failure.
- The Press