In 2007, the Australian Rail Track Corporation (ARTC) embarked on a major investment program to upgrade the rail track between Melbourne and Sydney. Since the program began, there have been a number of incidents and the condition of the line has been subject to significant adverse comment about its safety, largely in relation to rough ride characteristics and the existence and lack of remediation of ‘mud-holes’. On 16 August 2011, the Hon Anthony Albanese MP, Minister for Infrastructure and Transport, requested that the Australian Transport Safety Bureau (ATSB) undertake an investigation to examine (in broad terms) the safety of rail operations on the Melbourne to Sydney line.
In the course of its subsequent investigation, the ATSB found that the track structure between Melbourne and Sydney had historically been particularly vulnerable to degradation in vertical alignment, resulting in poor ride quality and mud-holes. While this was the result of a number of factors, major contributors were the weakness of the track formation (the earthwork foundation on which the track was laid) and ballast fouling (contamination of the aggregate material laid between the formation and the rails and sleepers).
In some locations, this pre-existing vulnerability had been increased by the track upgrade as a result of the process of installing new concrete sleepers. This exacerbated the problems of the pre-existing weak formation and reduced the effectiveness of the ballast. In addition, train forces on a weakened formation, as well as the effects of highly fouled ballast, poor drainage and heavy rainfall during 2010 and 2011, contributed to the development of mud-holes and poor vertical alignment. It is also possible that rail imperfections (localised defects) may have introduced concentrated impact loading that, when transmitted through the sleepers and ballast, may also have overstressed the formation in some locations.
The decisions made by the ARTC about the planning and execution of the upgrade project balanced safety, financial and operational considerations. The ARTC determined that the long term benefits of completely re-sleepering the track between Melbourne and Sydney were high. Safety improvements focused predominantly on controlling track gauge through the installation of concrete sleepers, while financial and operational considerations focused on minimal disruption to rail services and maximum track coverage (sleeper replacement) within financial constraints. The ARTC concluded that this was only possible if the side insertion method of re-sleepering was used and existing ballast was reused as much as possible. The upgrade program proceeded on this basis.
However, the ARTC’s quality assurance process during the project planning phase did not adequately consider foreseeable risks in relation to the track structure’s pre-existing vulnerabilities. It is possible that a more detailed examination of historical information and/or on-site testing may have highlighted any unknown track structure issues and influenced the decisions made prior to the re-sleepering works. Similarly, the ARTC was aware that the existing ballast and track drainage were in poor condition, but appeared not to have adequately considered the potential for higher than normal rainfall following a protracted period of drought. The ARTC believed the drainage problems could be addressed as part of ongoing maintenance programs, but has acknowledged that, following the track upgrade, the rate of track deterioration (including the development of mud-holes) was faster than expected.
During the early stages of the re-sleepering project, the quality control process focused on sleeper spacing, fastening of the rail to new sleepers, clearance of trackside infrastructure and the re-establishment of track geometry, but was inadequate with respect to ballast condition and depth of ballast under the new sleepers. During the course of the project, the procedures were updated based on additional identified risks, including the potential for formation damage due to inadequate ballast depth. The ARTC has since developed more detailed process documentation for side insertion of concrete sleepers. The updated process includes a stronger focus on quality assurance and recording of quality control data. In general, the ARTC appeared to have a quality assurance process in place that provided for identification of deficiencies, systems review and subsequent improvement to work practices.
It is unlikely that selecting an alternative method of re-sleepering would have prevented deterioration in track condition or the development of mud-holes, unless ballast, drainage and formation issues were also addressed. It is also likely that the cost associated with addressing the ballast, drainage or formation issues would have precluded completely re-sleepering the Melbourne to Sydney line with the funding available and therefore some residual safety risk associated with poor track gauge would have remained if this path had been chosen.
The track deterioration following the re-sleepering works required both short term management and the development of a longer-term major rectification program to maintain the operational effectiveness of the track. For the short term, an increased inspection and maintenance frequency, especially during periods of wet weather, was adopted. Where rail geometry defects were identified, actions were applied as specified by the ARTC (Track & Civil) Code of Practice. Pending rectification, the safety of train operations were maintained largely through the application of speed restrictions. These speed restrictions, together with increased maintenance activities, have resulted in extended train running times along the corridor.
While the application of temporary speed restrictions may in general control the safety risk, the system still relies on prompt identification of track condition hazards before the control measures can be implemented. If the track is performing in a constantly poor and degraded condition, there is an increased risk that defects compromising safety are not immediately identified. In this case, the ARTC have increased the inspection regime to mitigate this risk. However, if the system was performing well, it is likely to be inherently safer since it would place fewer burdens on the defect identification process.
The rail safety regulators in Victoria and New South Wales have, and continue to, actively monitor, audit and inspect the activities of the ARTC with respect to safety on the rail network. Regulatory intervention has resulted in the modification or development of processes aimed at ensuring the safety of rail operations. With the introduction of the Office of the National Rail Safety Regulator, this involvement has continued, but with a more national perspective.
Considering the combination of actions implemented by the ARTC and by the rail safety regulators, the ATSB is satisfied that safety of operations on the Melbourne to Sydney line has been maintained at an appropriate level, albeit with a requirement for greater vigilance to be applied to the inspection of deteriorating track conditions.
Longer term strategies ARTC implemented to rectify persistent problem areas on the line included a combination of undercutting and sledding to address ballast problems (fouling and depth) and track works targeting the correction of general drainage problems. While the treatments applied to date are likely to correct most ballast and drainage problems, the treatments are unlikely to correct the more deep-seated formation problems. Unless additional treatments are applied to improve the formation, it is possible that water will continue to weaken the structure in some locations, with a corresponding requirement for an increased regime of track maintenance (or some localised formation reconstruction) and the application of new or further speed restrictions.
Since the safety of the Melbourne to Sydney line remains dependent on the application of temporary speed restrictions, the ATSB examined the adequacy of the processes for applying such restrictions. The ATSB identified a number of opportunities where operational rail safety could be improved. This was detailed in an Interim Factual Report released in February 2012. The ARTC advised of their proposed actions in response and the ATSB is satisfied that those actions addressed the issues that were identified.
Both the initial upgrade and the subsequent rectification program led to a significant amount of track work being conducted on the Melbourne to Sydney line. This increased the likelihood of safeworking incidents involving track maintenance activities. The ATSB examined a number of reported safeworking incidents that occurred at various times between 2009 and 2012 and found that, in general, the safeworking rules and procedures were adequate as long as they were complied with. However, some of the incidents highlighted that protection methods for work on track were susceptible to human error, either through mistake or violation. In some cases, the safeworking systems were vulnerable to a ‘single point of failure’ which could increase the risk to rail safety. The ARTC, in consultation with rail safety regulators, has implemented changes to their systems for safely managing work on track and help protect against human error.
During the course of the investigation, rail operators also raised a number of specific concerns about the safety of the Melbourne to Sydney rail line. These related to elements of the signalling system, train parting incidents and quality assurance of track-related work. For signalling, the ATSB found that the principles applied to signalling design and the process for assessing signal sighting issues were consistent with recognised acceptable practice. For train partings, the ATSB found that track condition was a factor but not always the sole issue. Where deficiencies were identified, the ARTC issued additional instructions aimed at ensuring the safety of rail operations.
Taken as a whole, the ATSB is satisfied that the necessary steps have been taken to address any issues that might otherwise compromise the safety of rail operations where track quality is below acceptable operational standards. However, the actions taken to ensure safe operations have come at the expense of operational efficiencies through increased train running times.