A young Northland woman killed when a car crashed near Ōkaihau would probably have survived if she’d been wearing a seatbelt, a coroner has found.

The coroner’s report examines a July 29, 2020 crash that claimed the life of 26-year-old Aroha Tewhaia Erana Leaf and injured a relative.

Both were thrown from the vehicle when it veered off State Highway 1 just south of Ōkaihau, dropped into a stream and flipped, coming to rest in a paddock.

The surviving woman managed to get to the road and flag down a vehicle about 6.45am. She was flown to hospital with head injuries and other injuries.

Coroner AJ Mills said there were three key lessons to be drawn from the crash.

Leaf, who was thought to have been the driver, had an alcohol level of 266 milligrams per 100 millilitres of blood, or more than five times the legal limit for drivers aged 20 and over. Cannabis was also detected in her blood.

It was well-known that alcohol and cannabis affected driving ability by slowing reaction times, impairing co-ordination and dulling judgment.

A lack of seatbelt bruises, the retracted position of the seatbelt and the fact Leaf was thrown from the vehicle all suggested she was not restrained at the time.

The police investigator who examined the crash scene said she probably would have survived if she had been wearing a seatbelt.

Evidence such as the lack of brake marks and the time the crash occurred also pointed to Leaf being tired at the time of the crash.

Many fatal crashes occurred when the driver was fatigued, Mills said.

“I therefore reiterate these key messages: do not drink and drive; seatbelts save lives — always wear a seatbelt; and if you feel tired, do not drive.”

It was believed a party had been held at Leaf’s home near Ōkaihau earlier that night, but the circumstances leading up to the crash remain unclear.

It was not known, for example, why Leaf and her relative decided to leave her home sometime between 4am and 6.30am and head towards Ōhaeawai on State Highway 1.

Her relative had no recollection of the crash apart from waking up afterwards in the paddock.

Leaf, who was the mother of three young children, did not have a driver’s licence.

The crash occurred on a straight section of road in dry conditions.

■ Northland Road Safety Trust chairman John Williamson said 40 per cent of Northland’s road fatalities in 2020 were caused by the 3 per cent of drivers who don’t wear seatbelts. The figures for 2021 and 2022 were very similar — in those years, 38 per cent and 39 per cent of people who died on Northland roads, respectively, were not wearing seatbelts.