Mobile signals may be cut to probe Circle Line disruption, more staff deployed: LTA-SMRT

Temporary telecommunication signal suspensions could kick in and additional staff will be deployed to Circle Line (CCL) trains and stations as the Land Transport Authority (LTA) and SMRT grapple with the return of a signal interference that disrupted commuter travel on Wednesday (Nov 2) morning.

In a joint statement, the rail operator and the LTA said preliminary investigations indicate that the nature of Wednesday’s “intermittent loss of signalling-related communications” could be similar to that of the incidents that occurred on the CCL in early September.

Should similar signalling faults recur, the LTA and SMRT will work with the Infocomm Media Development Authority and mobile network operators to suspend mobile signals along stretches of the CCL for short periods.

In the meantime, all CCL trains will be manned during evening rush hour on Wednesday for faster response and recovery, as the morning’s faults caused several trains to come to a stop between stations. And delays were caused because SMRT staff had to make their way to the stalled trains to manually drive them back to station platforms.

The return of a mysterious signalling problem on Wednesday morning caused train services on the CCL to be disrupted for three hours, leading to services being suspended at six stations, including major interchanges Bishan and Serangoon.

The LTA-SMRT joint statement said “an interfering signal” could have disrupted communications, but its source “could not be conclusively established as those incidents subsequently stopped”.

The last time such signalling problems occurred was in early September, when the CCL was beset by five consecutive days of signalling issues.

Mobile signals for four stations were shut down for two hours on Sept 2 as the SMRT and LTA tried to determine the source of the interference, but with no results. And the signalling problems ceased as mysteriously as it started following that mobile service shut down.

LTA and SMRT said if mobile signals have to be suspended, announcements will be made in-train and in-station along the affected stretches.

Since then, the transport agency and rail operator had commenced feasibility studies to strengthen the existing signalling communications network, such as by placing an electromagnetic shield on the train to minimise the impact of interfering signals, or by changing the signal system frequency.