The transport safety watchdog is looking into whether faulty braking systems and driver fatigue were factors in a fatal freight train crash northeast of Perth.
A Pacific National freight train smashed into the rear of stationary grain train in the early hours of Christmas Eve, killing the driver and filling the cabin with grain.
The Australian Transport Safety Bureau said in a preliminary report on Monday the freight train was 14.5 km behind the grain train when it came to a stop behind a red signal at Jumperkine.
Shortly after the freight train driver acknowledged an alert from the vigilance system - a safety device that operates in case they are incapacitated - the train passed a stop signal while travelling at a speed of about 72 km/h.
Its speed gradually reduced as it travelled around a sweeping left-hand curve, where the driver apparently spotted the rear of the grain train and applied an emergency brake, but could not avert the collision 13 seconds later.
The ATSB said areas of investigation in coming months included the functionality of the locomotive's braking and vigilance control systems.
It will also look into factors affecting human performance such as fatigue and health and fitness, and review driver-only operations, noting Pacific National has added a second crew member to trains operating between midnight and 6am.
Australian Associated Press