A coroner says the driver of a car, one of four people killed in a crash near Lake Pukaki, was "too tired" and should not have been driving.
The crash, involving two cars and a motorcycle, happened on State Highway 8 (Tekapo-Twizel Road) between Hayman and Tekapo Canal Rds on March 30, 2024.
Three people, including two Canterbury University students from Malaysia and the motorcyclist, died at the scene.
Another three were airlifted to hospital in a serious condition and two people had moderate injuries.
A fourth person, one of the injured, later died in hospital.
One of the students had been driving four friends south from Christchurch in a Mitsubishi and briefly crossed the centre line before "cutting back in and overcorrecting".
The Mitsubishi flipped and rolled down the centre line towards the oncoming traffic.
It collided with the front of the Lexus.
Coroner Alexandra Cunninghame found that the driver of the Mitsubishi had only had three hours of sleep the night before.
"This terrible accident is yet another reminder of the danger of driving while tired.
"[The driver] chose to make a drive of several hours when he had three hours' sleep the night before, and after remarking to others that he was tired.
"Alarmingly, he was so tired that his front seat passenger had to massage him to keep him awake."
Toxicological analysis also confirmed that "a trace" of alcohol was found in the driver's blood.
But the report said this did not necessarily mean the driver had consumed or was affected by alcohol, and could have been due to "means other than deliberate ingestion".
Further evidence indicated that the driver was the only one in the Mitsubishi who had a licence.
"While this explains why he was determined to continue, he should not have been driving," Cunninghame said.
The Canterbury Serious Crash Unit had confirmed that no environmental factors contributed to the crash, with the weather that day fine and the road dry.
None of the three vehicles involved in the crash had any mechanical faults, the report said.
Both police and the NZ Transport Agency had undertaken campaigns to encourage drivers not to drive while fatigued, the report said.
"These campaigns include educating drivers about the risks and warning signs of fatigue, and about how to avoid it."
The coroner made further recommendations to the public about driving when fatigued.
"Drivers should get adequate rest before starting long vehicle journeys.
"Drivers should stop and rest properly if they become fatigued.
"Passengers should speak up if they become aware of a driver who may be too tired to safely continue, and should either offer to take over the driving or be prepared to break the journey until the driver is properly refreshed."
