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Passengers waited for CCL train on 20 September (Source : ahsa_sim Instagram account).

Electromagnetic shield to deal with “mysterious” signalling faults

The Land Transport Authority (LTA) and Singapore Mass Rapid Transit (SMRT) has issued a joint statement on investigations into the cause of the intermittent loss of signalling communications between the trains and tracks on the Circle Line (CCL) which had led to the automatic activation of the trains' emergency brakes.

They stated that a series of tests had been conducted with the train manufacturer Alstom and concluded that an interfering signal could have disrupted the trains’ signalling systems and leading to the loss of communications.

Engineers have tried to establish the source of the interfering signals over the past two weeks. However, as the incidents had ceased by the afternoon of 2 September 2016, they were unable to determine the source.

LTA and SMRT said that it would install spectrum analysers within the CCL tunnels to detect the presence of any interfering signal. This measure will be extended to the North East Line, which has the same signalling system.

They added that an electromagnetic shield would be placed on  trains to minimise the impact of interfering signals as part of feasibility studies to strengthen the existing signalling communications network. The possibility of changing the signal system frequency and/or modifying the system  in the event of signal interference would also be explored.

Between  29 August to 2 September 2016, the CCL experienced  intermittent signalling issues for five days in a row which caused a build up of commuters at stations and delay in travel times. On the first day, SMRT also alerted passengers to hold onto handrails as trains may experience intermittent braking.

Passengers at the station on 29 August (Source : Diana Teixeira Twitter account).
Passengers at the station on 29 August (Source : Diana Teixeira Twitter account).
Passengers at Yishun Station on 30 August (Source : Richard Jang Twitter account).
Passengers at Yishun Station on 30 August (Source : Richard Jang Twitter account).
Passengers at Bishan station (Source : Ariel Twitter account).
Passengers at Bishan station on 1 September (Source : Ariel Twitter account).
Circle Line jam on 2 September.
Circle Line jam on 2 September (Source : Twitter).

On 2 September, SMRT announced that mobile networks for Circle Line (CCL) would be  shut down for two hours  to  check for possible interference between the telecommunications network and train signalling system during peak hours when most of the incidents had occurred.

However, the fault still could not be found. So the SMRT and LTA are attempting  to use the electromagnetic shield on trains in an attempt for forestall signal interference. But without  establishing the cause, means the fault may reoccur  as it did on 20 September when  trains experienced 15 minutes slower traveling time which again caused delays.

Passngeres waited for CCL train at the station (Source : Ariel Twitter account).
Passengers waited for CCL train at the station on 20 September (Source : Ariel Twitter account).