The ATSB has found that a TransAdelaide passenger train passed a red stop signal last year, which placed it on a collision course with an interstate passenger train because of a combination of human error and sub-optimal procedures.
The Australian Transport Safety Bureau has today released its final report into the investigation of the factors that contributed to TransAdelaide passenger train H307 passing signal 161, at the end of a platform at Adelaide Railway Station, while it was displaying a red stop aspect, (an event commonly referred to as 'Signal Passed at Danger' or SPAD), on 28 March 2006.
The initial SPAD at signal 161 was typical of SPADs categorised as 'Starting Against Signal'. This type of SPAD typically occurs at railway stations where signals are positioned at the departure end of station platforms and the stationary train starts to move away from the platform before the signal displays a proceed indication. In this case, it placed train H307 on a collision course with the Indian Pacific which was on a crossing line 1.6 km from Adelaide station.
The investigation found that a conversation with station staff probably distracted the train driver's departure preparation. When scheduled to depart, a steady green light used by station staff to signal 'Right of Way' was a 'cue' which was in direct conflict with the red light displayed by signal 161. The investigation concluded that it was possible that the driver responded to the cue to proceed represented by the green Right of Way light and completed some minor tasks shortly after starting the journey but did not check the indication displayed by signal 161.
At the time of the incident, TransAdelaide's train control system did not provide a clear SPAD alarm. It is likely that an inexperienced controller, a period of high workload and the absence of a clear SPAD alarm contributed to a delay in train control personnel identifying that a SPAD had occurred.
The driver of train H307 believed that he had departed from the platform at Adelaide station under the correct signal indication and had been deliberately routed onto another track. The train had continued for two minutes and 610 m before the driver stopped the train. The driver's limited experience, his level of uncertainty regarding the unusual route and the absence of any information from the train controller to the contrary probably contributed to a delayed decision to stop and seek verification of the train's route.
The investigation noted that a new train control system was commissioned not long after the occurrence. The new system has audible and visual alarms to ensure that a similar SPAD should very quickly be recognised by train controllers. The investigation concluded that there were further opportunities for improvement. The ATSB recommended that TransAdelaide undertake further work to address safety issues relating to the SPAD investigation process and develop a clear understanding of SPAD causal factors such as potential underlying contributors to signal anticipation.
Copies of the report can be downloaded from the ATSB's internet site at www.atsb.gov.au