Impossible to find every flaw: SMRT chief Desmond Kuek

SMRT chief executive Desmond Kuek said the operator will not be able to catch every potential fault even if it stepped up maintenance.

"So one solution is to completely renew the system," he said. Another would be to put in place condition monitoring systems.

Mr Kuek said SMRT was doing all it could to make the network more reliable, but priority had to be given to the third rail, sleepers and signalling system.

"All these are multi-year programmes," he said. "And all these are being done while new trains are introduced into the system that need to be tested."

At the same time, SMRT is focusing maintenance efforts on "hot spots" such as the problematic Yew Tee-Kranji stretch.

"All these are conflicting sets of priority in terms of resources, time and manpower," Mr Kuek noted.

Mr Cedric Foo, chairman of the Government Parliamentary Committee for Transport, said a maintenance regimen had to be "codified" (arranged into a systematic code).

"For example, in aviation, there are very specific checks, namely A, B, C checks... It should become a drill of sorts with strict objective standards to be achieved and regular compliance assurance."

Meanwhile, SMRT is racing against the clock to uncover the exact cause of Tuesday's devastating disruption. The operator said a fault in a train, track or power system could have caused the electrical anomaly that triggered power trips across the North-South and East-West lines.

On this point, Mr Foo said it was "troubling" that when a relay tripped, it affected the whole network. "The question on people's minds is whether the relay can be wired such that the trip is isolated. Whether some 'redundancy' can be incorporated?

"Is it possible to fit a diagnostic system so that faults can be identified quickly? There are more questions than answers at this stage, and SMRT needs to do more."

National University of Singapore transport researcher Lee Der-Horng said the latest breakdown "exposed the weak resilience of the system". "Why was the system configured in such a way in the first place?" he said.