An Auckland passenger train derailed earlier this year due to the failure to interpret signals, an internal investigation has found.

The train, which was empty at the time, was operated by Transdev Auckland and derailed on Sunday, March 2.

A copy of the recently completed report has been sent to the New Zealand Transport Agency and the Transport Accident Investigation Commission - who are working on an independent investigation into the incident.

Transdev managing director Terry Scott said the report's findings had also been released internally so lessons learned could be shared and future incidents prevented.


"Safety is Transdev's highest priority. It is important that the investigation process is transparent and that we learn from any incident.

"The report doesn't seek to apportion blame but assesses risks, determines where improvements can be made and focuses on future actions and prevention."

The investigation found no infrastructure, train or signalling faults had contributed to the accident, however the likely cause was a failure to correctly interpret and appropriately respond to three signal aspects prior to the train's derailment.

The report also outlined a number of safety actions to mitigate the risk of future incidents, including working to assess the route risk, introducing non-technical skills training, reviewing roster practices and looking at upgrading one of the train protection systems.

Auckland's new electric trains use the European Train Control System - a protection system which would prevent a similar incident from occurring, Mr Scott said.

He thanked Transdev staff and KiwiRail personnel for their cooperation with the investigation on behalf of the reporting team.