Safety Issue
Considering the profile of the displaced shoulder ballast and
the absence of any evidence to the contrary, it is possible that
the combined effects of wind load, due to the prevailing
thunderstorm conditions, and the wagons' natural oscillations while
travelling, could have been sufficient to initiate the overturning
of the lightly loaded, double stacked, FQWY wagons in the
train.
Action taken by FreightLink Pty Ltd
FreightLink has implemented procedures to reduce the risk of
wind induced derailments by ensuring the combined centre of mass of
double stacked wagons is as low as possible. The gross mass of the
top tier container(s) must be equal to or less than the gross mass
of the bottom tier container(s).
ATSB assessment
Considering the extensive use of double stacked well wagons in
Australia and the very low incidence of wind induced derailments,
it is likely that FreightLinks action will reduce the risk of wind
induced wagon roll-over. However, there are actions other than
reducing centre of mass that may require consideration, especially
avoiding double stacking two large but empty containers on any one
wagon or platform.
Safety Recommendation
The Australian Transport Safety Bureau recommends that
FreightLink consider further action to address this safety
issue.