AN unmanned piece of mining machinery called Dozer DZ2003 was on a mission to move overburden at Peabody's Wilpinjong coal mine on May 27 until a 120-tonne excavator strayed into its automated path.
So Dozer DZ2003 hit it as it reversed, and when the manned excavator remained in its path and DZ2003 couldn't find its programmed GPS coordinates it hit the manned excavator again and again multiple times, until the control system faulted and the dozer stopped moving.
It was 14 seconds of crashing and defaulting that left the excavator driver unhurt but trapped in his cabin because his ladder was damaged, the NSW Resources Regulator said in an investigation report that led to increased safety measures when manned and unmanned machinery work in the same part of the mine.
Before the crash Peabody favoured separation bunds over some engineering controls to reduce the risk for manually-operated machines working near Wilpinjong's four unmanned dozers, and stop them from straying into the dozers' programmed operating areas.
Peabody said controls, including collision avoidance systems, were "not reasonably practicable" at the mine between Denman and Mudgee which employs 530 people and produced 12.6 million tonnes of coal in 2018, some to power Muswellbrook's Bayswater power station.
But after the crash Peabody installed a proximity awareness system and autonomous stop system to improve tracking of all vehicles and stop dozers encroaching on manned excavators' space.
"Instead of asking why an additional control should be implemented, this should be a question of 'why not?'," the Resources Regulator said in a report released last week that identified the mechanical and human causes of the collision.
Two avoidance systems weren't operating on the day so the excavator driver was relying on sight to operate near Dozer DZ2003, and the dozer's systems, and an operator working remotely could not see the location of the excavator.
Excavated material at different locations prevented the excavator driver from seeing three dozers working that day, and failed to stop his machine from travelling into the path of DZ2003 while it was reversing.
The Resources Regulator found staff were inconsistently trained in semi-autonomous tractor system task guidelines and procedures, and the specific working locations for the three dozers were not discussed before work started.
"The excavator operator believed the dozers were not operating in the northern area and thought all of the machines had been relocated during his break," the Resources Regulator said.
After the crash the excavator driver was unable to contact the control by radio because of radio traffic, but he was eventually released.
Resources Regulator chief inspector of mines Garvin Burns said the incident was of particular interest because of the increasing use and trials of autonomous and remote-controlled equipment in NSW mines and the opportunity to pass on lessons learnt. Peabody introduced the first semi-autonomous dozer at Wilpinjong in 2015.
"The investigation identified a number of contributing factors to the incident including poor sight lines and a breakdown in communications," Mr Burns said.
"However, of even more importance, the investigation and subsequent actions by the operator identified a number of key engineering and technology measures that have since been implemented to prevent re-occurrence.
"Any mine operator using or considering the use of autonomous machinery should review the full investigation report to see if any of the lessons can be applied to their operations."