Mystery of Circle Line's signalling problem solved

Mystery of Circle Line's signalling problem solved
PHOTO: The Straits Times

SINGAPORE - The mysterious signal interference which interrupted service on the Circle Line MRT in recent months is a mystery no more.

According to the Land Transport Authority (LTA) and train operator SMRT, investigations showed that signalling problems on the Circle Line were caused by an intermittent failure of the signalling hardware on one train.

Between Nov 2 and 6, the hardware failure on the train - No. 46 - had caused trains in the proximity of it to lose signalling communications.

The loss of communications on these trains resulted in their emergency brakes being automatically activated as a safety measure.

It is believed that the same problem was what caused the loss of signalling communications on Circle Line trains between Aug 28 and Sept 2.

An initial hypothesis - that interference from telecommunications signals may have caused the repeated activation of the trains' emergency brakes - was tested and proven wrong.

Train No. 46 was tested at its manufacturing location as well as under local conditions before it was deployed in June 2015, LTA and SMRT said in a joint statement.

At the moment, it remains unclear why the train's signalling hardware has been experiencing intermittent failure.

The statement added that no other train has been found to have the same hardware issue.

No. 46 has since been pulled out of service, and an examination will be carried out on the signalling hardware for the rest of the fleet.

ljessica@sph.com.sg

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