Victoria’s regional rail operator will install authority-overrun protection at a signal near Southern Cross station, following a near collision between two passenger trains there last year.
On the afternoon of 23 November 2020, a loco-hauled V/Line passenger train left Melbourne’s Southern Cross station for a service to Melton.
Shortly after departure, the train passed signal SST535, under the LaTrobe Street road-over-rail bridge, at about 23 km/h, despite the signal instructing the train to stop. This is known as a signal passed at danger (SPAD) event.
The train continued for about 200 m beyond the signal, before stopping across a junction which was about to be passed through by a second passenger train.
The second train, a three car V/Line VLocity train operating a Wendouree to Southern Cross service, stopped about 100 m from the junction, following an emergency broadcast from the controlling signaller.
The subsequent investigation into the near-collision, conducted on behalf of the ATSB by Victoria’s Chief Investigator Transport Safety, determined the driver was probably distracted by task-unrelated thoughts when they passed signal SST535, and probably looked past the signal to another, further along the track, which they incorrectly believed to be the signal where they were to stop.
“Once signal SST535 had been passed, the risk control to reduce the likelihood of a collision was primarily the action of the Southern Cross signaller to respond to system alarms,” Chief Investigator Chris McKeown said.
“In this instance, the signaller responded by making an emergency broadcast to the Wendouree to Southern Cross service and this was sufficient to stop that train. The driver of the Melton train also overheard this broadcast and stopped their train.”
Some signals around the V/Line network are equipped with a Train Protection and Warning System (TPWS), which can automatically brake a train when a SPAD occurs.
While both trains were equipped to receive signals from a TPWS system, trackside TPWS transmitters were not fitted at signal SST535 at the time of the incident.
During a 2014 risk assessment to determine which signals on its network warranted TPWS functionality, V/Line did not consider a head-on or side-on collision to be a credible scenario as a result of a SPAD at signal SST535.
“Had a front-on or side-on collision been considered a credible scenario in the 2014 risk assessment, the risk rating of the signal probably would have led to the fitting of TPWS.”
V/Line has advised that funding was approved in July 2021 to install track-mounted TPWS transmitters at a number of signals in the Southern Cross area, including signal SST535. The operator plans to complete this installation in 2022.
Additionally, the investigation also found the absence of ‘flank-track’ protection increased the risk of a potential collision in this incident.
Where a train’s route is set over a junction, flank-track protection requires the tracks between a signal protecting a converging route and the junction to be clear before the signal will display a proceed aspect.
In this instance, flank-track protection could have directed signalling to instruct the driver of the VLocity train to stop when the SPAD occurred.
“V/Line signalling standards did not identify flank-track protection as a control to prevent collision because of a SPAD, and none was installed at the incident location,” Mr McKeown said.
“Flank-track protection was also not identified as a potential control to prevent collision because of a SPAD in the signalling standards, administered by the Rail Industry Safety and Standards Board (RISSB).”
RISSB has advised flank-track protection will be considered for inclusion when the signalling principles standard AS 7711 is next under review.
“This occurrence has highlighted the importance for passenger rail networks to have engineering controls in place to detect SPAD events and prevent potential consequences such as collision,” Mr McKeown concluded.
“In determining applicable SPAD risk controls, rail operators should consider all SPAD precursors, and potential collision scenarios.”Last update 07 December 2021