On 12 February 2013, intermodal freight train 3MC1 derailed at Locksley, near Seymour in Victoria. The train consisted of two locomotives (GL107 leading and GL101 trailing) hauling 33 wagons having a trailing mass of 921.1 t and an overall train length of 885.5 m. There were no injuries but the last eight wagons derailed and about 800 m of track was damaged.
What the ATSB found
The ATSB determined that the derailment of freight train 3MC1 at Locksley was most likely the result of a track misalignment at the 127.768 km mark on the West Line of the interstate mainline. Hot weather in the period preceding the derailment, and trains travelling along the track, probably caused a redistribution of longitudinal rail stresses in a northerly direction towards the derailment site. The track structure near the derailment site probably had a reduced capacity to withstand lateral forces, due to track quality (ballast contamination). This, coupled with maintenance activities close to the derailment site, most likely initiated a redistribution of longitudinal forces towards the 127.768 km mark and increased the likelihood of a track buckling event.
What's been done as a result
Australian Rail Track Corporation track maintenance staff have been provided with additional training on the consequences of multiple track disturbances altering the stress free temperature of rail track. The training will provide an enhanced level of compliance with the requirements of procedure ETM-06-06 (Managing Track Stability - Concrete Sleepered Track).
Following the derailment and subsequent reinstatement of the track the Australian Rail Track Corporation undertook stress free temperature testing at ten sites near the ‘Point of Derailment’. Tests established that the rail stress free temperature was within specified tolerances.
The Australian Rail Track Corporation has implemented a ballast remediation program on the Melbourne – Sydney rail corridor. This work will continue as programmed until completed, following which further works will be undertaken at sites having identified formation weakness.
Track managers must consider the potential impact of track disturbing maintenance activities on lateral track stability, particularly in areas having poor ballast quality and during periods when temperatures are significantly higher than the rail neutral temperature.