Wiremu Armitage was almost five times over the legal drinking limit when he crashed into Kirsty Parsons, killing her and himself.
Both Parsons, 26, and Armitage, 31, died after their vehicles collided on Taihape Rd, Omahu, on May 10, 2019.
A coroner's report found that Armitage was solely to blame for the double fatal, after his truck crossed the centre line and collided head-on with Parsons' hatchback.
Toxicology analysis reported alcohol in Armitage's blood at 241 milligrams of alcohol per 100 millilitres of blood – 191mgs above the legal limit for driving.
No alcohol or drugs were found in Parsons' system.
A post mortem conducted by forensic pathologist Amy Spark found Parsons died of multiple injuries as a result of a motor vehicle accident.
Armitage, who was not wearing a seatbelt, was ejected from his vehicle and died from multiple injuries.
Senior Constable Dougal Watts said Armitage failed to negotiate a left-hand bend, driving over the centre line into the path of Parsons.
Examination of the rear bulbs showed Parsons did have her brake lights activated, while Armitage did not.
Constable Watts said the "lack of emergency action" was down to Armitage's alcohol intake and fatigue.
"The main causative factor in this crash was the driver of the Toyota, Mr Armitage," he said.
The report found Parsons was not a contributing factor in the crash.
On the day of the crash, Armitage spent the day building and fixing his new boat with his friend Steve Jude, before retrieving two boxes of beer from his ute.
Armitage told Jude he was going to drive home but considered getting a taxi because he was unsure if he would be over or under the legal limit.
Jude reminded Armitage there was always a police checkpoint at Fernhill Bridge and it was not worth the risk, and Armitage left his car keys on the bonnet of his boat, before having another drink.
Later, Jude noticed Armitage was gone, assuming he'd taken a taxi home after consuming an estimated five and a half beers over the course of several hours.
On the same night, Parsons had dinner with her partner David O'Sullivan in Crownthorpe.
Unable to get to sleep due to hearing a rat in the wall, Parsons decided to leave O'Sullivan's house and go home, despite O'Sullivan urging her not to drive home.
At 10.20pm, the cars collided killing them both.
Road markings on Taihape Rd were found to be in good condition and clearly visible, while mechanical faults were not found to be a factor in the crash.