The Pacific National broad-gauge freight train, No. 9204V, was travelling from Warrnambool to Appleton Dock, Victoria. Due to track works at West Footscray Junction—to repair damage arising from a previous derailment—the train was despatched from Tottenham Yard toward the port via an alternative route, the adjacent dual-gauge Main line. Track circuit failures resulting from the track damage meant that Up-direction Home signals on the Main line were displaying Stop indications, and for this reason the train had departed Tottenham yard on the authority of a Signalman’s Caution Order. The locomotive crew received two further Caution Orders en-route, the last of these being for Home signal DYN158.
Signal DYN158 protected a turnout that provided for a diverge of the standard-gauge line away from the broad-gauge, and the network control officer (NCO) had inadvertently set this turnout for a standard-gauge movement. The locomotive crew proceeded past the Home signal and through the points, resulting in derailment of the locomotive and one wagon at low speed.
What the ATSB found
The ATSB found that the NCO had established a standard-gauge route beyond signal DYN158 rather than the required broad-gauge route. Although the Train Control System software incorporated an on-screen gauge alarm to warn an NCO against setting an unviable route, in this instance that screen alert did not appear, since its generation was contingent on the gauge detection system that was not functioning. The signalling system had been degraded as a result of a previous derailment.
The Train Control System permitted the NCO to establish a route on an incorrect gauge for train 9204 and displayed that route as viable.
What's been done as a result
ARTC has introduced provisions to ensure that modifications made to the Phoenix Train Control System display are fully understood by Control Centre staff, and has also modified the Signalman’s Caution Order form to provide explicitly for the checking of the intended route and for the train crew to check the setting of points to be traversed.
The ATSB has recommended that ARTC undertakes further action to address the risk of directing trains onto incorrect gauge track in dual-gauge territory.
When the signalling system and the functionality of safety intervention devices is degraded and an alternative process of safeworking is in use, there is a need for a heightened level of awareness and caution on the part of network control officers and train crew.
When designing control system safety mechanisms, such as the Gauge Alarm in this instance, the rail operator should consider all possible sub-system failures to ensure the intervention remains effective under all circumstances.