Safety experts are examining whether the driver of the XPT which fatally derailed in Wallan was aware of track diversions which caused the speed limit to drop from 130km/h to 15km/h.
The Australian Transport Safety Bureau's interim report found the train was travelling between 144 km/h and 127km/h when it entered the Wallan Loop turnout, which has a speed limit of 15 km/h, and derailed on February 20.
NSW Trains driver John Kennedy, 54, who was based at the Junee depot, and accompanying qualified worker Sam Meintanis, 49, were killed.
Earlier that month on February 6 arrangements were made that trains would go straight through Wallan's main line rather than via the Wallan Loop, after a fire caused extensive damage to signalling controls.
Trains can travel through Wallan's main line at 130km/h. On February 19, ARTC issued a notice advising trains would be diverted through Wallan Loop for a short period on February 20.
ATSB observed NSW Trains and its drivers were "probably not aware" of the notice or track diversion.
The notice was not directly released to NSW Trains, and NSW Trains did not routinely check ARTC's WebRams where it was uploaded.
Mr Kennedy had run the Junee-Melbourne-Junee round trip four times between February 8 and 19, during which the Wallan Loop was not used and the speed limit was 130km/h.
A signal to warn trains to slow down near the track was not working on February 20.
The ATSB report indicates during an unrelated discussion a controller told the driver 'you're going via the loop there at Wallan'.
The driver's response did not reference the change. Other than that comment there was no explicit communication between the train driver and controller about the track diversion or the 15km/h speed limit.
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An in-field signaller had been informed and had read back the train authority which detailed that the Wallan loop was set. It was procedure for the in-field signaller to give the AQW the completed train authority form before the AQW boarded the driving cab of the train.
At 7.30pm the driver confirmed to the controller he was in possession of the authority, but neither read it out loud to confirm details.
A risk assessment completed on February 6 did not directly look at risks associated with routing trains through Wallan Loop, but did rank the risk of 'rail operators not aware of the altered working' as low. To mitigate risks, ARTC included a note that AQWs were to advise the drivers of the change.
NSW Trains has since amended its procedures so crew must confirm receipt of safety information, while ARTC has developed a new risk assessment tool.