The ramp had been constructed in the morning to link two work areas but was partially excavated during the day.
Due to the incline of the ramp, the light vehicle driver couldn't see that the ramp had been partially removed.
The front wheels went over the edge and the vehicle bellied out on the open edge.
The NSW Resources Regulator said the occupants were able to exit the vehicle safely and did not suffer any injuries.
"The ramp had been excavated without any delineation markers, windrow or positive communication to the light vehicle operators," it said.
"Mine operators should ensure that appropriate barricading standards are applied in instances where ramps or roads are excavated, or edges are exposed.
"Changes to roads and other vehicle operating areas should be communicated to affected workers."
The regulator is currently investigating a similar incident in which a light vehicle drove over an open edge and fell 12m following the excavation of a ramp.
