Four members of the Lee family were killed after a fatal collision with a truck north of Tokoroa in February.
Warren Lee, 53, Aesoon Lee, 52, and their 20-year-old daughter Julia Lee died in the crash.
Julia's brother Griffin, aged 17, died in hospital later.
Mr and Mrs Lee were American citizens living in Hong Kong.
Their daughter had been living and studying in Massachusetts and was due to start studying at the University of Auckland a few days after the crash.
"The Toyota turned in my path"
The hearing before Coroner Gordon Matenga began in Hamilton District Court at 10am.
Truck driver Timothy Manderson was first to give evidence on the first case involving Mrs Barnett and her friends on SH39.
He told the coroner he was travelling south when he saw the grey SUV heading towards him.
"As I approached the vehicle, the Toyota turned in my path. As they did that I hit my brakes as hard as I could and the front of my truck hit the front passenger door," he said, choking back tears.
"I'm not exactly sure what happened but then my truck pushed the car until it came to rest on the other side of Tuhikaramea Rd."
Mr Manderson received minor injuries.
When questioned by the coroner, he said he didn't see Mr Barnett's face before impact as he was concentrating on the road ahead.
"I think he was indicating it he didn't stop, he just kept going."
He was familiar with the road and travelled it many times.
Tuhikaramea man Russell Court was travelling behind the Barnett's but was to continue north a few minutes home.
He wasn't looking at the SUV when he drove past it but noticed that it had indicated.
"It then moved into the slip lane to turn and as he arrived he almost came to a stop. At this point I was two car lengths behind still in the northbound lane.
"I then saw it turn right but there was a B-train coming south. The SUV turned straight into the path of the truck giving the driver absolutely no chance to take evasive action."
Constable David Tidmarsh of the Waikato serious crash unit said Mr Barnett told police he couldn't remember the crash, but in a television interview said he didn't see the truck itself.
"That's not totally unusual. We have many crashes around the district where drivers simply don't see other road users ... usually lesser sized vehicles though."
When questioned by the coroner about Mr Barnett's inexperience of driving in New Zealand - on the opposite side of the road to America - he agreed that he likely simply wasn't expecting the truck to pass on his right hand side.
"He may have expected that vehicle to travel down his left side."
Asked for his view on the ability of foreign drivers in New Zealand, Mr Tidmarsh said he could only comment on Waikato's statistics and they were in line with the national average.
"I wouldn't drive overseas myself, in a country whew the road rules differ greatly to my own, but that's coming from my own experience I suppose and how things can go so wrong."
Wrong side of the road
Julia Lee was driving on the wrong side of the road, and had been for some time, before her vehicle collided head-on with a logging truck on the outskirts of Tokoroa, the inquest heard.
Constable Bayley Orr, of the Taupo serious crash unit, told the coroner the truck's cab crashed 800mm into the front right side of the Toyota, forcing the vehicle backwards south across the road and into a ditch bordering the north bound lane before coming to rest about 37m south of the area of impact.
She said Miss Lee's actions were "intentional, but I believe she thought she was driving within the correct lane, however not correct for New Zealand".
"On Julia's approach to the crash scene there's a right hand bend and two passing lanes on the opposite side of the road. She was in the inside passing lane right up against the bend, so she would still have been following that curve of that corner and then she's come round and seen the truck ... and she's tried to take last minute evasive action."
Miss Lee's parents only had a seven day visa to be in New Zealand, arriving on February 15, with the purpose of helping her settle into Auckland University.
The family had just stayed the night in Taupo, and had completed a bungy jump on the day of their death before setting out on their fatal journey north.
Asked for her opinion on overseas drivers, Ms Orr said she had only attended two fatal crashes involving tourists.
However, the road policing unit was regularly called to non-serious traffic incidents involving tourists crossing the centre line or driving too slowly.
Miss Lee and her parents all died at the scene. Her brother, Griffin, died in hospital days later.
Her parents, sitting in the back, were not wearing seatbelts and were thrown from the vehicle on impact.
"It is unknown whether they would have survived the crash had they been wearing their seatbelts however the left rear side of the Toyota was relatively undamaged and not in the path of the principal directional force so it is likely that had any of them been belted in to the left rear seat then the injuries received would have been much less significant than those in the front and right side."
Coroner Matenga reserved his findings.
