Judge Greg Cavanagh said heavy drinking was also involved with some of the car passengers, primarily the driver.

A warning - the following information identifies Indigenous people who died in the accident.

Four people - Robin Riley, Thomas Turpin, Fabian Andrews, and Cassandra Martin all died at the highway's Bukbukluk turn-off.

A fifth women, from Katherine, who cannot be named, survived after a heroic effort to get help.

The intersection is located about 80km from Pine Creek.

Several of the victims were from Katherine.

Judge Cavanagh said all four were in a car which left the Mary River Roadhouse after a long drinking session on October 1, 2018 although not all four had been drinking.

While police at the time of the tragedy believed speed may have been involved this was dismissed as a possible cause during the recent inquest.

Instead it was found Mr Riley, who was driving, later recorded a 0.27 per cent blood alcohol level at the time of the rollover.

Only two of the people in the car were wearing a seat belt when the accident happened, about 18km from the roadhouse.

"Because of the dark and the lack of traffic on the highway, the accident was not noticed until the following morning. The first on the scene were Kakadu Rangers," the inquest was told.

One of the back seat passengers was thrown from the vehicle and was found near the crash the next morning still breathing, but died before emergency services could get him to hospital.

Another passenger, a Katherine woman, later scrambled in the dark from the vehicle determined to get help.

"She walked to the highway," Judge Cavanagh said.

"There were no lights and no vehicles approaching. She returned to the crashed vehicle, kissed the driver on the forehead and then headed up the road toward Jabiru following the white line on its edge.

"Her left shoulder, arm and hand were broken. She took off her bra and made a sling. She walked until she needed to rest. She thinks she slept a little.

"By morning she had walked about 12 kilometres. The third car that passed her was occupied by Italian tourists. They stopped for her and took her to the Health Clinic at Pine Creek. From there she was evacuated to Royal Darwin Hospital where she spent a week before being released."

The police Major Crash Unit calculated at the time the vehicle started to lose traction it was travelling at 101kmh (in a 110kmh zone).

Loose gravel was strewn on the edge of the highway which police calculated reduced friction by a third.

"In the opinion of the Major Crash Investigators, the curve was also a 'substandard curve' meaning that if the Highway had been to Australian Standard 1742.2 it would have had an advisory speed of 90km," Judge Cavanagh said.

The shoulders of the highway were not sealed.

"Since 2008 there had been one death on Kakadu Highway every year or two. However, 2018 had been a particularly tragic year on the Highway. Prior to these deaths there had been three crashes in which five people had died. Due to those crashes DIPL had sought a comprehensive independent audit of the Kakadu Highway. The audit commenced shortly after this crash," the inquest was told.

That audit found 1250 areas where improvements were recommended.

Judge Cavanagh said: "There were clearly a number of aspects that led to the crash that ended these peoples' lives.

"It is evident that the road surface was not in an appropriate condition given the speed limit of the Kakadu Highway at that point."

He said the drinking of the driver which had impaired his reactions plus the adverse road conditions contributed to the crash.

Judge Cavanagh recommended:

"I recommend that the Department of Infrastructure, Planning and Logistics ensure that removing gravel from sealed surfaces is added to the schedule of maintenance items.

"I recommend that the Department of Infrastructure, Planning and Logistics ensure that an apron is installed as soon as possible on the road to Bukbukluk Lookout to prevent gravel from being deposited on the Kakadu Highway."