John Linwood, 56, was alone in a Toyota HiLux ute when he crashed into the rear of a loaded coal haul truck at the Byerwen mine in Queensland's Bowen Basin on August 22, 2024.
There were two theories on the crash's cause, counsel assisting Michael Nicolson told coroner Wayne Pennell on Thursday at a pre-inquest conference in Brisbane.
"An investigation by Resources Safety and Health Queensland submitted the most likely cause of the incident was that Mr Linwood suffered a medical episode," he said.
"(The episode) resulted in the vehicle he was operating striking the haul truck, killing him instantly."
Investigators also found cheese and crackers in the HiLux's console and theorised Mr Linwood could have looked away from the road and toward the snack momentarily before the crash, due to it being lunch time.
"Ultimately this theory was found to be plausible but less likely than the medical episode," Mr Nicolson said.
Mr Linwood was an experienced and competent driver, and the crash occurred in fine and sunny weather on a compacted dirt road that had not had recent rain, the court was told.
He had been taking an antibiotic and a toxicology report found an antihistamine at levels that would not have contributed to the crash.
The haul truck was travelling at 12km/h up an incline while taking coal out of the pit.
Mr Linwood was travelling at 38km/h.
"Moments before the incident the utility increased speed to 46km/h," Mr Nicolson said.
The HiLux's roof was crushed down to the bottom of the windows and its bullbar wedged underneath the truck's rear axle as a result of the crash.
Byerwen is an open-cut mine with 800 personnel running operations 24 hours a day and seven days a week, Mr Pennell heard.
The ute and the truck had no mechanical problems before the crash.
The mine has road rules that includes light vehicles having to keep a distance of 50 metres when driving behind a haul truck.
Mr Linwood was a contractor for mine operator Macmahon and had been assigned general duties as his drill rig was not operating that day.
His death was the second within a month at the mine, with 48-year-old Chris Schloss killed in a crane incident.
An inquest into Mr Linwood's death was scheduled to start on June 8 with seven days of hearings.
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