The coroner has found poor driving to be the primary cause of a deadly bus crash on Mt Ruapehu in 2018.
In July 2018, the crowded skifield shuttle overturned after its brakes failed halfway down the steep Turoa ski field road.
Hannah Francis, 11, of Auckland, who had been on the learner slopes with her father just hours before, died on the way to hospital.
Three people were seriously injured.
The 119-page coroner's report faults driver Sung-Pil (Terry) Choi's habit of not using his gears properly to hold back the bus - a habit that went uncorrected by shuttle and skifield operator Ruapehu Alpine Lifts.
However, Coroner Windley said numerous other factors contributed to the crash, including that the bus was operating at its design limits and with a type of brakes known to be prone to overheating and failure.
"The inquest revealed just how narrow the margin for brake and gear selection mismanagement was, and the resulting knife-edge between an uneventful journey and a catastrophic one down Ohakune Mountain Road," Windley said.
"While the bus was capable of undertaking the journey safely...it was operating at the edges of its design envelope.
"The margin for driver error was smaller than it might be in a bus specifically designed for alpine environments."
In her report, Windley made 11 recommendations aimed at making alpine transport safer, including beefing up a voluntary code of practice.
The code was introduced last year in response to Hannah's death but operators are still not audited in a comprehensive way, and the coroner urges regulators to check on companies.
Windley praised Hannah's parents and step-parents for their "quiet dignity and strength" as they sought answers over why she died.
The families jointly issued a statement thanking the coroner.
"Although nothing will bring our Hannah back, we are all very pleased with the findings and recommendations detailed in this report.
"We are optimistic that these will go a long way to preventing such a tragedy happening to another family."
Police did not press charges after the crash, though a senior police officer told the inquest a year ago he may have been wrong not to charge the driver.
No health and safety investigation took place - police thought one was underway, but it was not.
It was of continuing concern that the relationship between police and WorkSafe "appears plagued by confusion and miscommunication", the coroner said.
Police said their criminal investigation of the bus driver was "thorough" but did not reach the threshold for prosecution.
Police had already targeted vehicles, including buses, for safety checks twice this year during school holidays under what was dubbed Operation Hannah, said the relieving assistant commissioner Deployment and Road Policing Steve Greally.
"Hannah's death was an absolute tragedy as is any life lost on our roads," he said.
"Police remain extremely committed to reducing the number of deaths and serious injuries on our roads."
Police were working on some of the other coronial recommendations around audits and educating operators.
Their partnership with WorkSafe was strong, Greally said.
The coroner has reopened the case and Ruapehu Alpine Lifts (RAL), and its employee, bus driver Sung-Pil (Terry) Choi, could still face prosecution.
Windley said there were grounds to look at possible breaches of health and safety laws by the company, or the driver, or his supervisors.
WorkSafe has a six-month deadline to take any legal action.
The Coroner's Act prevents the agency from using documents obtained during the coronial process in any prosecution but it can use the evidence from open court.
It is a highly unusual situation as the coroner's findings almost always come last.
WorkSafe said in a statement that the coroner has noted there was considerably more information available about the crash now, than at the time.
It also said it had improved how it worked with police to investigate crashes, including having monthly meetings about cases, under an Memorandum of Understanding updated last year.
"While we acknowledge the issues identified in this situation, both agencies are confident they have been resolved," WorkSafe told RNZ.
"WorkSafe is confident that the collaborative approach that comes from working closely with police will achieve better outcomes for victims and investigations."
It accepted the coroner's recommendations to audit bus companies over the Alpine Code, and to develop an education campaign for drivers, and would work on them.
An ex-driver for RAL told RNZ in 2018 of being scared at the state of the buses, and passengers spoke of bus seats held together with string, and armrests falling off.
RAL stopped operating shuttles after the crash.
The coroner's report says the customised "flicker chain switch" on the dash of the bus that crashed, used for dumping air to boost traction, was an "extraordinarily dangerous feature" that went undetected for years.
It was "deeply concerning" Certificate of Fitness (COF) inspections by VTNZ had not picked up on the switch, she said.
The switch was meant to have been disabled but was still active - yet a warning light on the dash for the switch had been disconnected.
"The wires to the light were disconnected and there was also no bulb present."
VTNZ defended its inspections at the inquest, saying mandatory checks covered standard parts of vehicles, not customised ones.
VTNZ said the transport industry owed it to Hannah and her family to "learn from this tragedy and make sure it doesn't happen again".
"Although VTNZ's actions were not at fault, we have enhanced our Certificate of Fitness training materials for new vehicle inspectors in regard to air braking systems and auxiliary devices," VTNZ told RNZ.
"VTNZ will also continue to encourage all inspectors to check for any little things that are out of the ordinary."
The coroner questioned the type of buses RAL used on the steep run, its driver training and in particular, Choi's habit of using a high gear on descent.
"RAL's evidence to my inquiry has failed to explain how such a bad habit was not identified and addressed in the context of a driver training programme RAL seeks to portray as robust and rigorous."
RAL then-chief executive Ross Copland was unable to give the inquest details about driver training and monitoring, Windley said.
Choi had made the Turoa trip hundreds of times but said he did not do refresher training in 2018 and had only learned "on-the-job" how to manage brake fade.
The 1994 Mitsubishi Fuso had a brake system "understood by most experienced drivers to be at risk of failure from overheating unless the vehicle's braking resources are carefully managed by the driver," the coroner said.
"Brake fade can set in rapidly" and there was little a driver could do.
Widespread checks of Fuso buses were undertaken after the crash.
One of the new recommendations to the government and regulators is to make a new alpine transport code mandatory, setting out standards for vehicles and drivers.
The Bus and Coach Association helped bring in the voluntary code last year, prompted by Hannah's death.
It strongly recommends members sign up if they work on gravel or risky roads at altitude, or skifield access, association chief executive Ben McFadgen said.
While the association audits members' for compliance, it cannot audit non-members, though they are free to adopt the alpine code too, he said.
RAL was not an association member at the time of the crash, McFadgen said.
It "unfortunately was just running a bus that wasn't suitable".
RAL did not ask the association for advice on what type of bus it was using, he said.
Many of the shuttle services have been taken over since the crash by Dempsey Buses - an association member; others by Ruapehu Mountain Transport, which the association said was not a member - the company declined to comment to RNZ.
The coroner also recommended regulators take another look at making seatbelts mandatory on alpine buses.
In a statement, RAL said its thoughts were with Hannah's family and friends, and also all of the people who were on the bus that day.
Chief executive Jono Dean said they backed strengthening the alpine transport code that said RAL initiated after the crash, and law changes to bring in seatbelts on buses.
"We don't want an accident like this to happen again and we will support whatever measures that are necessary," he said.
Queenstown operator NZSki which runs two dozen 4WD shuttles at ski fields helped draw up the voluntary code.
Chief executive Paul Anderson said it was a "no-brainer" to make it mandatory.
NZSki was not a ready fit with the bus association, but it would consider becoming a member if the code remained voluntary.
"The public has got the right to expect a very, very high level of safety and training," Anderson said.