After months of investigation on the mysterious signal interference causing Circle Line (CCL) disruptions, it turned out that the culprit was the faulty signaling hardware on one SMRT train, Passenger Vehicle 46.
The said train had caused trains in its proximity to lose signaling communications, triggering emergency braking as a safety feature, said Today in a report on 12 November 2016.
This has seen mobile signals shut down on the entire line for a day, and military experts brought in.
Incidents have happened on about 100 occasions on 2 November and 6 November 2016. It is also likely that the same hardware failure was behind about 200 such occurrences between 28 August and 2 September 2016.
The Land Transport Authority (LTA) revealed these details on Friday, 11 November 2016, and added that the affected train has since been removed.
Further investigations will be carried out to find out what caused the hardware in question to break down. The rest of the CCL fleet will also be checked.
CCL issue "shows the value of multi-agency approach to solving problems"
Since the interfering signals were first detected on the CCL in late August, various steps were taken by the authorities to get to the bottom of the case.
These include reverting to old signaling software, checking station equipment, and putting in place portable scanners in trains to pick up anomalies. Mobile signals were also suspended on the train on three separate occasions, but the authorities found that CCL trains continued to lose communications during the blackout.
Engineers and data scientists from the Defence Science and Technology Agency (DSTA) and the Government Technology Agency of Singapore (GovTech) were roped in to investigate. After poring through the information on system logs and applying data analytics, the authorities picked up a trend of Passenger Vehicle 46 being in the vicinity of almost the signal faults.
In a Facebook post on Friday 11 November, Defence Minister Ng Eng Hen lauded the teams from DSTA and DSO National Laboratories - who were also involved in the CCL investigations - for using their expertise to identify the source of the stray signals.
LTA will continue to explore the use of electromagnetic shields on trains as part of measures to minimise interfering signals.
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