A New Zealand man was negotiating a steep hill in the Otira Viaduct for the first time when his brakes gave out, causing him to slam into the back of another truck. The force from the hitting the truck was so strong, that it propelled the man 30 meters through a guardrail and right off the side of a gorge, ultimately killing him.

Police senior crash investigator Senior Constable Simon Burbery said at the time of the crash there was light fog and the road was wet. It was still dark. The crash investigators found Mr Jones had crossed the centre line and hit the steel netting used to hold back rocks. The truck was travelling no less than 38-40km/h when it hit the barrier. The trailer landed on the cab unit, which was crushed.

Blood tests showed he had smoked the equivalent of a single cannabis joint within three hours of death.

Constable Brett Currie found a plastic bag with cannabis at the accident scene.

The coroner said the truck was too damaged to determine what gear it had been in. If it had been in low third gear and the retarder on high, there would have been little or no need to apply the brakes. “I consider it most likely that lack of experience in driving down the Otira Gorge in the hours of darkness has resulted in driver error by failing to engage the correct gear before descent, and resulting in brake applications that has resulted in brake failure,” coroner Devonport said.

The coroner could not exclude fatigue or the effect of cannabis, or a medical event.