Discontinuation notice published 27 March 2020
Section 21 (2) of the Transport Safety Investigation Act 2003 (TSI Act) empowers the ATSB to discontinue an investigation into a transport safety matter at any time. Section 21 (3) of the TSI Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation. The statement is published as a report in accordance with section 25 of the TSI Act, capturing information from the investigation up to the time of discontinuance.
Overview of the investigation
On 12 February 2018, the ATSB commenced an investigation into a loss of tractive effort on train 8466 at Ardglen, New South Wales (NSW), which occurred on 10 February 2019.
Train 8466, operated by Qube Logistics, was planned to transport mineral concentrate from Cobar, NSW, to Port Waratah, NSW. During the journey, 10 wagons were added. This required the addition of another locomotive, which was attached at Werris Creek.
The train departed Werris Creek with three diesel-electric locomotives (QBX005, QBX004 and QBX001) hauling 61 wagons with a total length of 961 m. The train crew consisted of two drivers.
After pausing briefly at Chilcotts Creek, the train made its way up the 1 in 40 grade to the Ardglen Tunnel, until its speed dropped and it came to a stop near the distant signal on the approach to Ardglen. The driver inspected the locomotives but did not identify any problems.
The driver restarted the train, but soon after locomotive QBX001 began to perform erratically, intermittently losing tractive effort. The locomotive began to provide tractive effort again, and the train accelerated to 18 km/h and entered the northern portal of the tunnel at 11 km/h.
About 2 minutes after entering the tunnel, locomotive QBX005 derated to produce no tractive effort, and within another minute, the other two locomotives also derated to produce no tractive effort. The tunnel was filled with exhaust smoke, which entered the lead locomotive QBX005’s operating cab and reduced the drivers’ visibility.
When the driver sensed the train was moving again, he assumed the locomotives were producing tractive effort, but the train was actually rolling backwards towards the northern portal of the tunnel. When the train approached the tunnel’s exit, the driver realised the problem and made a full service brake application. The second driver made an emergency call to train control, who advised the track behind the train was clear and the points were set correctly to protect the train movement. Ultimately, the train rolled back a total distance of 982 m. Although this was an unplanned event, communications between the train crew and train control at all stages ensured protection was in place.
As part of its investigation, the ATSB interviewed the drivers, reviewed the train’s event recorder data and obtained loading records for the train and other trains used by the operator. The ATSB also obtained and reviewed the operator’s investigation report on the occurrence.
Based on this information, it was identified that:
- The train’s initial documentation, prepared by the train crew, indicated that the 61 wagons weighed 4,636 t (76 t per wagon). A subsequent calculation by personnel in the operator’s customer service centre, and entered into the operator’s transport management system prior to the train’s departure, was 4,392 t (72 t per wagon). This latter weight was erroneous, and after the occurrence the actual weight was determined to be 4,608 t. However, the operator reported that the locomotive capability for the planned route was 5,148 t (1,716 t per locomotive), in excess of the actual weight.
- The locomotives were manufactured in 2015. Locomotive QBX001 had previously experienced derating issues due to its exhaust sensor not operating consistently to deliver accurate temperature readings to the locomotive management system. It had recently been repaired and certified by an external contractor, which involved a temporary repair of a wiring harness. However, during the occurrence sequence, the locomotive continued to experience intermittent faults with the exhaust sensor.
- Ardglen Tunnel had no exhaust or gas ventilation or artificial illumination. When in the tunnel, exhaust gases from the locomotives surrounded the locomotive bodies and were forced forward of the locomotives, resulting in the ingestion of exhaust gases into the locomotives’ engine air intakes.
- There was no requirement for an operator to carry oxygen self-rescue units in the lead locomotive of a train passing through the Ardglen Tunnel, although such units were required for operating through the Ulan Tunnel (which the train normally operated through). Such oxygen self-rescue units were on board locomotive QBX001, but the crew had not transferred them to the lead locomotive QBX005 (nor were they required to do so).
- The driver was presented with ambiguous and incomplete information when the three engines derated. He saw that the lead locomotive had derated, but there was no visual indication that both the trailing locomotives had derated, and no audible indication that the trailing locomotives derated. While in the tunnel, the driver sighted the speed indicator consistently displaying a speed above 0 km/h, but the indicator did not differentiate between forward and reverse speed.
- The operator identified several proposed actions to improve the safety of its operations.
Based on a review of the available evidence, the ATSB considered it was unlikely that further investigation would identify any systemic safety issues. Consequently, the ATSB has discontinued this investigation.
The evidence collected during this investigation remains available to be used in future investigations or safety studies. The ATSB will also monitor for any similar occurrences that may indicate a need to undertake a further safety investigation.