22.02.18
RAIB to investigate Cambrian line ERTMS failure
The RAIB has launched an investigation into the loss of speed restriction data to trains during an incident on 20 October on the Cambrian coast line.
A driver travelling on the line in North Wales reported that longstanding temporary speed restrictions were not indicated on their in-cab display.
The temporary speed restrictions were required on the approach to level crossings so that people crossing the line had sufficient warning of an approaching train.
In 2011 the Cambrian lines were equipped with a pilot installation of the European Rail Traffic Management System (ERTMS), which removes the requirement for signals along the track by transmitting data directly to the train.
Movement authorities and information such as temporary and permanent speed restrictions are displayed to the driver on a screen.
Signalling staff at the Machynlleth control centre investigated this report and became aware that the same failure applied to several trains under their control.
A subsequent investigation revealed that the signalling system had stopped transmitting temporary speed restriction data after a routine shutdown at around 23:10hrs the previous night.
But there was no indication of an abnormal conditioning, and signalling control centre displays showed the restrictions as being applied correctly.
To date the signalling system supplier has not identified the cause of the failure, so the RAIB has decided to undertake an independent investigation.
The organisation claims that there is a possibility that had suitable data been downloaded from the signalling system before it was restarted during the correction of the failure, it may have assisted in establishing the cause.
In its investigation, RAIB aims to consider the geographic extent of the failure and the effect it had on the safety of railway operations, why trains were permitted to operate without information about temporary speed restrictions, and the practices for gathering data needed for investigations before restoring computer based signalling systems.
At the conclusion of the investigation, RAIB will publish its findings and any recommendations to its website.
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