Singapore blocks mobile signals in bid to identify mystery train fault

Plagued with a mystery signalling fault that has disrupted train services multiple times, Singapore has resorted to blocking mobile communications in a desperate bid to identify the cause of the problem.

The country's Circle Line (CCL) experienced "intermittent loss of signalling-related communications" on Wednesday that caused delays at several train stations during morning peak hour, said Land Transport Authority (LTA) in a joint statement with train operator SMRT. A train stalled between stations, disrupting service at affected stations including two interchanges Bishan and Serangoon.

Initial investigations suggested the faults were similar to a spate of delays that occurred in September, which also impacted CCL services, LTA said. The cause of the signalling fault then was unidentified as the problem did not resurface, after it disrupted train services for five consecutive days.

In the weeks that followed, LTA and SMRT had attempted to boost the existing signalling communications network, such as using an electromagnetic shield on trains to buffer the impact of signal interference as well as changing the signal system frequency.

It also switched off mobile signals at four stations during evening peak hour in an attempt to identify the source of the signalling fault. Commuters waiting at these stations were unable to make phone calls, SMS, or browse the web during the suspension. "The mobile signals need to be turned off during these two hours as we are checking for possible interference between the telecommunications network and train signalling system during peak hours when most of the incidents have occurred," LTA then said.

However, its efforts failed to establish the cause of the problem.

With the return of the signal interference this week, LTA said it would be working with ICT regulator Infocomm Media Development Authority (IMDA) and local mobile operators--M1, StarHub, and Singtel--to once again suspend telecommunication signals along the CCL. This would kick in if, and when, similar signalling faults return, the transport authority said.