A runaway freight train reached speeds of up to 107km/h as it careered down one of NSW's steepest rail lines near Wollongong.
The danger of the over-laden grain train running into other trains was averted only after rail network controllers cleared a path for it as it sped uncontrolled down an Illawarra mountain between Dombarton and Unanderra in April last year.
Details of the incident are contained in a final report by the Australian Transport Safety Bureau, which found the driver did not adhere to handling procedures and that the train, operated by Qube, was carrying about 10 per cent more load than had been recorded.
Yeah mate, we are in emergency braking running away down the hill. Over.
After passing Summit Tank, the driver's decision to apply the brake on 10 occasions meant he had not given the train's pneumatic brake system time to fully recharge.
This led to the loss of braking capability to slow its speed.
Compounding the situation, the driver's actions caused the locomotive's dynamic braking system to be rendered inoperative, further reducing control of the 664-metre long train.
The driver first noticed he had a problem about 26 minutes after passing Summit Tank when the train was travelling at 20km/h. Within seconds, the train's speed had risen to 30km/h.
He tried unsuccessfully on several occasions to slow the train's speed before shifting its automatic brake handle to an emergency position.
Despite applying the maximum braking, the train's speed rose to 46km/h.
Applying the automatic brake to the full emergency position deactivated the dynamic braking system, which meant there was nothing he could do to stop the train gaining speed.
The driver then radioed the Australian Rail Track Corporation's control centre, telling an operator: "Yeah mate, we are in emergency braking running away down the hill. Over."
The controller then quickly alerted Sydney Trains that the Qube train was running away, and heading towards lines it controlled. A minute later, a Sydney Trains controller confirmed that a route for the runaway train had been cleared and there was nothing in its path.
Rounding a curve approaching Unanderra station, the train reached a top speed of 107km/h, and it was not until it later reached an incline that it began to reduce speed.
Later, the driver told investigators that Illawarra Mountain deserved "a lot of respect".
The safety bureau said the incident showed freight operators needed to ensure drivers were trained regularly and assessed for competency on steep gradients to reduce the risk of runaway trains.
"Contingency plans and procedures to accommodate runaway trains in this area should be continually reviewed and tested by rail infrastructure managers," it said.