Rail safety investigations & reports

Parting of Metro Trains Melbourne passenger train TD 3817 at Croydon, Victoria on 9 November 2018

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

Download final report
[Download  PDF: 2.45MB]

What happened

A six-car Metro Trains Melbourne (MTM) passenger train travelling from Flinders Street Station to Lilydale Station uncoupled shortly after leaving Croydon Station. The train consisted of two 3-car units and uncoupled at the mid-coupling. The train was travelling at about 78 km/h when the 3-car units uncoupled. The trailing car unit came to a stop under automatic emergency braking. Once the train driver noticed that the trailing car unit had uncoupled, he applied emergency braking and brought the lead unit to a stop about 300 m from the trailing car unit. There were no injuries in the incident.

What the ATSB found

It was found that two technical faults had combined to cause the uncoupling. Inspection and testing conducted by MTM revealed that a wiring error was made during a modification to the train’s low-note whistle on the lead car of the train. Further, there was a deterioration of insulation resistance in the uncouple solenoid connector of the lead car of the trailing car unit. The low insulation resistance of the uncouple solenoid combined with the incorrect wiring of the low-note whistle resulted in an error circuit forming to energise and actuate the uncouple solenoid. This resulted in the unintended uncoupling.

What's been done as a result

The X’Trapolis fleet was inspected by MTM. Eleven of the motor cars were found to have the low-note whistles wired incorrectly and these were rectified. The low-note whistle wiring document has been updated to provide further clarity and to prevent future wiring errors with respect to this modification. In addition, maintainers involved in low-note whistle modification work have been briefed and re-trained on the modification method statements. Further, completed modification work will require self-checks and supervisor checks.

MTM advised that it has implemented a program of mandatory insulation resistance testing of the uncoupling solenoid connectors. The information from the testing will be provided to the original equipment manufacturer in order to assist with determining the root cause for the failure and take appropriate remedial action.

MTM further advised that it is reviewing the scope for improving negative to ground testing during depot based scheduled maintenance and exploring a design for a system for monitoring common negative to ground potential.

Safety message

This incident highlights the importance of ensuring that a verification program is incorporated into quality assurance systems to mitigate the risk of errors during installation or modification of electrical systems.

Download final report
[Download  PDF: 2.45MB]

The occurrence


Safety analysis


Safety issues and actions

Sources and submissions

Safety Issue

Go to RO-2018-019-SI-01 -

Wiring error was not detected

The wiring error was not detected by Metro Trains Melbourne’s verification program.

Safety issue details
Issue number: RO-2018-019-SI-01
Who it affects: Passenger rail transport operations
Status: Closed – Adequately addressed
General details
Date: 09 November 2018   Investigation status: Completed  
Time: 1658 EST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): Croydon, 32 km from Flinders Street Station, Melbourne   Investigation phase: Final report: Dissemination  
State: Victoria    
Release date: 09 October 2019   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Train details

Train details
Line operator Metro Trains Melbourne  
Train operator Metro Trains Melbourne  
Train registration TD 3817  
Type of operation Passenger  
Sector Passenger - metropolitan  
Damage to train Nil  
Departure point Flinders Street Railway Station, Victoria  
Destination Lilydale Railway Station, Victoria  
Last update 11 October 2019