In the lead up to the October 5 incident the experienced dozer operator was working on a tip head.
The truck operator arrived at the tip head and was unsure where to unload but recalled an earlier instruction from the dozer operator to tip against the wall.
The truck operator reversed to dump the load.
The truck operator heard a thud and stopped the truck.
That thud had come from the haul truck and dozer colliding.
The haul truck operator had 11 weeks industry experience and four weeks experience at the mine.
The NSW Resources Regulator has started an investigation to determine the cause and circumstances of the incident.
"The investigation will, among other things, consider communication between the operators, training and supervision, as well as adequacy of policies and procedures relevant to the incident," it said.
The mine operator is cooperating with the investigation.