The death of a young father, who was decapitated by a flying truck part on an Auckland motorway 17 years ago, is being re-examined in a rare second inquest.
John Edward "Eddie" Tavinor was driving his ute north on Auckland's Southern Motorway, near Penrose, in November 2000 when the part from an oncoming Mitsubishi truck's drivetrain broke free and flew like a missile through his windscreen, according to a witness report at the time.
The truck was driving in a south-bound lane.
Three witnesses at a coronial inquest held two years after Tavinor's death agreed the drivetrain's failure was caused by a bearing failure.
Coroner Murray Jamieson's 2003 report said mechanics servicing the truck had critically failed to notice the drivetrain was worn and unsafe and had also failed to follow correct procedure when reinstalling it.
However, engineers Peter Morgan and Timothy Smithson, are challenging some of these expert findings in a new coronial inquest that opened on Monday in Auckland at their request.
Smithson said the failure of the Mitsubishi truck's drivetrain was more likely the result of a design flaw that he argued was present in a number of trucks plying Kiwi roads
He showed pictures of other trucks that had suffered drivetrain failures and also had critical parts break off.
In one case, a drivetrain failure in a truck on a motorway caused a heavy part to fall off and be hit at speed by a trailing Honda Civic carrying two people - damaging the car but fortunately not hurting any one - he said.
In another case, a part broke free and hurtled down the road, missing a man walking his dog by half a metre, he said.
However, two earlier witnesses working in the trucking industry said the most common causes of drivetrain failure were due to poor maintenance on the vehicles.
They said they were not aware of a catastrophic gearbox or drivetrain design flaw affecting trucks on roads in New Zealand or around the world.
The inquest is expected to continue for one week.