The ARTC Code of Practice does not clearly address the possibility that a series of track irregularities, even minor ones which do not exceed intervention limits, could cause an undesirable harmonic response in some rail vehicles.
Examination of wagon RCPF31882C revealed a crack on the tread of a wheel on the second axle of the leading bogie. While not contributing to this derailment, if the crack were to develop to such an extent that the wheel tread completely fractured, the risk of derailment would increase significantly.
The trailing bogie of wagon RCPF31882C was found to have loose and broken wedge wear plates. It could not be verified whether the wedge wear plates had broken free before or during the derailment sequence. However, if the condition had existed prior to the derailment, it is likely that body roll induced while traversing a series of track irregularities could result in undamped harmonic oscillations.
Manual systems of train management, such as Special Proceed Authority working, are used when interlocked/engineered systems are not available. However, manual systems are subject to human error and increase the risk of safeworking irregularities/incidents when compared to interlocked/engineered systems of safeworking.
