Metro Trains Melbourne has installed new electronic lubricators and changed its track management procedures after a derailment near Rushall station in Melbourne’s north-east in February 2016.
Melbourne Metro Train TD1064 was citybound on the South Morang Line (now called the Mernda Line), when it derailed between Merri station and Rushall station, in north-east Melbourne on February 6, 2016.
The train comprised two 3-car X’Trapolis sets coupled as a six-car train.
The leading bogie of the second car derailed on a small-radius curve heading into Rushall station around 4:50pm on the day in question.
The train came quickly to a stop. There was one minor injury reported.
The Australian Transport Safety Bureau, which handed in its final report into the incident earlier this year, said the derailed car was foul of the adjacent track and there was potential for more serious consequences had a train from the opposite direction been passing at the time.
The ATSB found that leading right-hand wheel of the train’s second car had climbed the outside rail curve. Contributing factors were the high coefficient of friction between wheel and rail, and the geometry of a rail joint.
“The train was being operated within the speed limit for this curve and the manner of its operation did not contribute to the derailment,” the Bureau noted.
Five days after the derailment, a track regulator derailed on the same curve, a short distance from the first incident.
Lubrication an issue
“It was found that the train’s wheel flanges and the rail’s gauge-face had low levels of lubrication,” the Bureau noted.
The report states the outer rail at the point of derailment was clean and dry, with no visual evidence of either lubricants, or contaminants and with a roughened surface. Below the worn gauge-face there were steel filings on the rail foot and ballast.
“The presence of both the rough gauge-face surface and metal filings below the rail were indicative of high friction and wear conditions and hence indicated a probable deficiency of lubrication between gauge-face and wheel-flange.”
The Bureau’s report found the performance of rail lubricators on Melbourne’s metropolitan network had diminished prior to the derailment, “probably the result of a decline in lubricator maintenance”.
“Rail lubricator maintenance was being transferred from contractors to Metro Trains Melbourne (MTM) staff and this transition was not adequately managed,” the Bureau said.
MTM uses mechanical rail lubricators, known colloquially as ‘grease pots’, to dispense grease to the rail gauge-face at certain locations. The grease pot intended to prepare trains for the Rushall curve, travelling towards Melbourne, was located roughly 20 metres past Merri Station, around 330 metres before the curve.
Throughout 2015, maintenance for MTM’s grease pots was contracted out to Sunstone Resources. MTM documents show the last monthly inspection of the grease pot in question took place in December 2015, but after that the contract with Sunstone was ended, with MTM to take over grease pot maintenance and inspection.
“MTM advised that it had been difficult to organise safeworking arrangements for access to the track during this transition period and that lubrication activities were subsequently fully re-established in February 2016 … monthly inspection and maintenance had been conducted through to December 2015, [but] no further maintenance had then occurred until after the derailment (on February 6, 2016).”
Curve was unique
In addition to lubrication, the Bureau found the derailment could, potentially, have been avoided with changes to the track.
“The derailment at this point on the curve was triggered by a lateral angular discontinuity at a mechanical rail joint, resulting in a localised increase in the wheel-to-rail lateral force,” the Bureau wrote.
“The network’s track geometry standard did not preclude the presence of such a discontinuity.”
Known as the ‘Rushall curve’, the section of track is a 118-metre radius-curve, the most severe mainline curve on the MTM network. It had a permanent speed restriction in the Up direction of 30 km/h at the time of the incident.
“This small-radius curve existed as a remnant of a triangular junction that originally connected the (then) Epping Line to the Royal Park-to-Northcote Loop (also known as the Inner Circle Line),” the report states.
“The connection was severed in 1965 and the Royal Park-to-Northcote Loop was subsequently closed. The curve that formed the junction’s eastern leg remained as a portion of the main line between Merri and Rushall Stations.”
Travelling towards Melbourne, the Rushall curve is on a 1-in-70 downgrade, and was constructed using wooden sleepers supporting typically 13.7-metre rail joined by mechanical (fishplated) joints in a staggered pattern.
Around the point of derailment, rails were on double-shoulder base plates generally attached by plate screws, and were mostly secured using resilient fasteners with some use of dog spikes, the ATSB report explains.
“The most recent MTM engineering inspection of the curve was on 2 March 2015 at which time the track was reported as being fit-for-purpose for one year,” the report states.
“Examination of the track following this derailment found evidence of pumping and angular misalignment at mechanical joints. The gauge-face of the outside rail (high leg) had sustained noticeable side wear.”
The Bureau’s report suggests the presence of a check rail on the Rushall curve, installed adjacent to the inner rail, would have provided an additional defence against flange-climb and derailment.
“A network standard to potentially address derailment risk at higher-risk locations was under consideration at the time of this derailment,” the Bureau wrote.
In addition to these factors, the Bureau identified a number of other safety factors that were “not directly causal” to the derailment. These include the ineffective locating of some rail lubricators within the network, a high tolerance on allowable track geometry deviations at this and similar low-speed mainline locations, and a failure to address a wide-gauge defect on this curve, according to the final report.
Communications failed driver
While not a contributing factor to the incident itself, the ATSB identified communications as an issue in its aftermath.
Immediately after the derailment, the train’s driver was unable to contact Metrol via the train’s radio system, and subsequently established contact using a company-issued mobile phone, about six minutes after the derailment.
“It was another minute before any approaching rail traffic could be halted,” the Bureau said.
What’s been done as a result
Since the derailment, MTM has shifted to a new maintenance schedule for its grease pots.
“MTM advised that their maintenance plan required that lubricators be inspected every three months, although up to December 2015, lubricator inspection was reportedly on a monthly cycle,” the Bureau reported.
“MTM track managers were aware of the specified maintenance cycle of three months and this may have influenced them in taking several months to establish an effective lubricator maintenance regime.
“Fleet rolling stock wheel condition indicated that the degree and standard of network rail lubrication had started declining in December 2015 and had further deteriorated through January and early February 2016. The most probable reason for this deterioration was a reduction in the effectiveness of rail lubrication across the network. This probably resulted from inadequate lubricator maintenance during the transition from contracted to internal maintenance.
“MTM was aware of the fleet-wide deterioration in wheel condition, but the response was inadequate to prevent this derailment.”
The operator has also taken on new advice as to where its grease pots should be located.
Specialist advice presented to MTM in 2000 and 2007 suggested track lubricators should be located at the lead-in to the target curve, but “many of the lubricators examined during these studies were located on sections of tangent track distant from the curves being serviced,” and more recent advice suggests this is not a suitable position for efficient lubrication.
“A recent MTM audit found that 43% of lubricators were in fact located on tangent track,” the ATSB said. “This would have resulted in an inefficient use of lubricant and the potential for lubricator performance to be less effective than desired.”
The lubricator intended to service the rail in question in this incident was located on tangent track in advance a curve.
“This would have led to less-effective pick-up of lubricant, and where pick-up did occur, too much of that lubricant being deposited directly back onto the track,” the Bureau said.
Since the incident, MTM has updated its rail lubrication strategy based on an assessment of alternative lubrication technologies. This has resulted in the roll-out of electronic lubricators across the network, with technical information and training to support this change.
The operator has also implemented a network-wide lubrication strategy resulting in the relocation of many of the mechanical lubricators, until they are replaced by electronic lubricators.
Radio system addressed
It was found the train’s Digital Train Radio System (DTRS) did not allow a Train Emergency Call to override an initial lower-priority call in the aftermath of the derailment.
As a result, “MTM has enhanced its driver training to highlight the operation of DTRS for normal and emergency use, including the need to cancel a lower-priority call prior to initiating an emergency call,” the Bureau reported.
“MTM is also reviewing the functionality of similar digital radio systems used by other rail operators, and options for changing the functionality of the DTRS.”
The ATSB said MTM had taken additional safety steps in light of the investigation. This included a number of proactive safety actions.
“MTM has introduced new and revised standards for wheel turning and flange surface roughness,” the report states.
“MTM has also established a program of cultural change that has included re-training in the management of track defects and reinforcement of accountabilities.”