Rail safety investigations & reports

Derailment of freight train 6DA2 near Marla, South Australia on 31 October 2015

Investigation number:
Status: Completed
Investigation completed

Final Report

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What happened

At about 1050[1] on 31 October 2015, Genesee & Wyoming Australia train 6DA2 derailed near Marla, South Australia. The derailment resulted from a package bearing failure on wagon FQWY 12-F. The wagon and three other container wagons were significantly damaged and there was significant damage to the track. There were no injuries.

What the ATSB found

The ATSB found that the journal and bearing on wagon FQWY 12-F had seized and lost interference fit. The loss of interference fit generated high levels of frictional heating between the bearing and the axle journal, and the subsequent torsional shearing failure of the axle (commonly referred as a ‘screwed journal’). The axle failure caused the axle and wheels to stop rotating, resulting in one wheel skidding along the railhead for approximately 50 km, before derailing.

On the balance of the available evidence, the ATSB concluded that a loss of lubrication was the most likely contributor to the bearing breakdown and seizure. Evidence also suggested the breakdown developed relatively rapidly, given the absence of a positive fault detection from two bearing acoustic monitoring systems (RailBAM) passed on the previous day of the occurrence.

Safety message

Bearing failures leading to derailment continue to occur within the Australian rail network. Rail operators must continue to be vigilant and ensure axle bearings are correctly installed, maintained, and monitored throughout their life.

Screwed journal
 Screwed journalSource: Genesee & WyomingScrewed journalSource: Genesee & WyomingWhat happened
Source: Genesee & Wyoming


  1. The 24-hour clock is used in this report and is referenced from Central Daylight Time (CDT)
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The occurrence


Safety analysis


Additional safety action

Sources and submissions


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General details
Date: 31 October 2015   Investigation status: Completed  
Time: 1050 CST   Investigation level: Systemic - click for an explanation of investigation levels  
Location   (show map): About 30 km north of Marla    
State: South Australia    
Release date: 13 July 2017   Occurrence category: Accident  
Report status: Final   Highest injury level: None  

Train details

Train details
Line operator Genesee & Wyoming Australia  
Train operator Genesee & Wyoming Australia  
Train registration 6DA2  
Type of operation Freight  
Sector Freight  
Damage to train Substantial  
Departure point Darwin, NT  
Destination Adelaide, SA  
Last update 03 April 2020