Inquiries into the deaths of three Mongrel Mob members in a crash in Northern Hawke's Bay 10 months ago have revealed the sole survivor of their 125m plunge into the Mohaka River was likely to have been the only one wearing a seatbelt.
A report by Coroner Chris Devonport quotes survivor Anthony Atkinson as telling a police officer at the scene the driver of the Honda Inspire "just lost control and we went over".
"I was just lucky I was wearing my seatbelt," he was reported to have said.
Reports say none of the three men killed appeared to have been wearing restraints.
Police found Mr Atkinson on the river bank a few metres from the wreck in the Mohaka River near Raupunga. He was capable of walking, had a graze on his face and bruises near one elbow, police officer Mike O'Brien said.
But the crash, as the car left the State Highway 2 Mohaka Viaduct underpass, killed driver Ronald Rangi Rigby, 53, and the other passengers, Terry Shane Stone, 31, and Nathan Conway Isaac, 29.
The four men were on their way to a weekend gang reunion at Te Aute in Central Hawke's Bay when the crash happened in fine weather about 2.45pm on November 7 last year.
Police inquiries established it happened moments after a second vehicle, a Honda Prelude, attempted to overtake the car carrying the men.
They concluded the men's car crossed the centreline and contact between the two vehicles appeared to have forced the second car into the Armco barrier designed to prevent vehicles crashing over the side.
The second vehicle braked heavily and stopped against the railing, but the men's car rode along the top of the barrier, touched the edge of the bank at the top of the drop and plunged into the river.
The Prelude left the scene and was found in the Raupunga area several days later.
Police said they could not establish who was driving at the time of the crash, and those they believed were in the vehicle declined to make statements.
No evidence was found to support laying any charges against its driver.
The inquiry found methamphetamine detected in the blood of Mr Rigby and evidence of his use of cannabis, but Coroner Devonport refrained from commenting in his "formal finding".
Reports do not record any methamphetamine being detected in the blood of the passengers.
The toxicologist said in a report to the inquiry epidemiological evidence suggests methamphetamine adversely affects the skills necessary for safe driving.
"It may be dangerous to drive after using psychostimulants due to over-confidence in driving skills that is not supported by an actual improvement in driving ability," the toxicologist's report said.
Coroner Devonport found all three men died from injuries received as the Honda Inspire tumbled down the near vertical bank and came to rest about 125m from where it left the road.