WorkSafe has charged the company the runs the Turoa ski field and Vehicle Testing New Zealand as a result of a bus crash that killed 11-year-old Aucklander Hannah Francis.
Francis died and three other people were badly injured when the bus' brakes failed and it overturned halfway down the Ohakune Mountain Road in July 2018.
Ruapehu Alpine Lifts has been charged with two breaches of the Health and Safety at Work Act, while VTNZ has been charged in relation to technical aspects of its Certificate of Fitness certification process.
Ruapehu Alpine Lifts' chief executive Jono Dean said it had fully co-operated with the coronial inquest and WorkSafe investigation.
"RAL respected and agreed with the coroner's recommendations, and has made significant changes to its transport operation since this tragedy," he said in a statement.
"At the time of the incident, RAL notified WorkSafe. It is regrettable that WorkSafe (through an apparent breakdown in communication with NZ Police) did not investigate the accident at the time and that, nearly four years after the accident, charges have now been laid."
Dean said the company had been instrumental in forming the Alpine Code of Practice to reduce the risks of transporting passengers in alpine environments.
He said Waka Kotahi should adopt the code as a minimum standard in the alpine transport industry.
"It is RAL's hope that this type of accident never occurs again," Dean said.
"RAL extends its thoughts and sincere condolences to (Hannah's family) for the loss of their daughter."
VTNZ's country manager Greg O'Connor said the company was reviewing WorkSafe's action.
"We were deeply saddened by the death of Hannah Francis in 2018. As an industry we owe it to Hannah Francis and her family to make sure we learn from this tragedy and make sure it doesn't happen again," he said.
"The coroner's inquest into the accident found that matters relating to VTNZ played no role in the fatal accident."
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 Ruapehu Alpine Lifts.
WorkSafe has been contacted for comment.