Scene evidence had clearly shown that excessive speed was not a factor in the incident and Constable Robinson considered that the "actions or inactions" of Mrs White had to be considered the prime factor in the crash.
Evidence was given by Mrs White's husband Ross White who told the inquiry his wife had been in good health and had not seen a doctor for over a year.
They had a quiet day on New Year's Eve, the day before the crash, and a roast lunch before Mrs White drove her daughter to the station the next day.
Kirsty White said she had helped her mother with a mosaic craft project then spent the rest of the day with her until catching a 4pm train out of Masterton.
She told the inquiry Mrs White "hates driving a manual car, but it was her car and she has had it for eight years."
Kirsty White said on the way to catch the train they had talked a lot and her mother was her usual "not-so-confident driver".
"What I mean is that she sometimes got muddled with the gears and would sometimes go around corners in top gear.
"She was careful and drove at normal speed.
"She knew the road really well," Kirsty White said.
The coroner said the likely reasons for Mrs White failing to negotiate the left-hand bend, or to take action to "regain the roadway" was that she was either distracted, fell asleep or suffered a medical problem.
But, because of the time of day and the circumstances of the previous 24 hours it was unlikely she had fallen asleep.
Dr Katherine White, who carried out the post-mortem on Mrs White's body, was of the opinion she had died from the spinal injury and considered it unlikely Mrs White had suffered a medical event that caused her to crash.
"There is insufficient evidence to say definitively why Mrs White failed to negotiate the slight left hand bend, cross the centre line and take no action to return to the road," Mr Devonport said.
