Final Report

Summary

What happened

On 15 December 2015, train ND575 – a south bound empty bulk iron ore service operated by Rio Tinto, derailed on the Hamersley Railway east mainline, about 50 km north of Tom Price, Western Australia. As a result of the derailment, there was significant damage to track and rolling stock. There were no injuries.

What the ATSB found

The ATSB concluded that the derailment most likely began with a small horizontal track misalignment on the east mainline, just south of the Mt Brockman Road railway crossing. It was likely that the misalignment grew under train ND575, and eventually became large enough to cause the train to derail. The pathing of a large number of north-bound loaded ore trains on the east mainline probably caused a redistribution of longitudinal rail stresses south of the Mt Brockman railway crossing. This redistribution of rail stresses, coupled with extremely hot weather, and a track irregularity near the point of derailment, meant the track had a reduced capacity to withstand lateral forces, thereby increasing the likelihood of a track buckle event.

What's been done as a result

Rio Tinto have implemented a range of initiatives to reduce the risk of a similar occurrence including changes to operational and maintenance procedures, enhanced strategies for responding to minor track irregularities, and a strategy for balancing tonnage over the line.

Safety message

Early detection, assessment, and effective management of track defects are critical in minimising the risk of derailment and maintaining safe rail operations.

Derailed portion of train ND575, view looking north from ore car 20322

Derailed portion of train ND575, view looking north from ore car 20322. Source:  Rio Tinto

The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions