It is now known that the massive breakdown last October, which left more than 6,700 passengers stranded on trains across three MRT lines for up to three hours and affected about 123,000 commuters directly, was caused by a combination of factors: an inherent manufacturing defect in power cables or mishandling during installation led to a cut in cable insulation, which resulted in a short circuit. Then, circuit breakers, which would have isolated the cable fault, failed because components had rusted and effectively prevented the circuit breakers from tripping. These findings of a months-long forensic investigation into equipment faults on the Tuas West Extension, which led to disruptions on the North-South, East-West and Circle Lines, afford an insight into a disruption that caught commuters off guard both in terms of its extent and its duration. The main lesson from the findings is that a major disruption is caused by the confluence of a few small glitches occurring simultaneously and is sufficient to paralyse a large segment of train lines.

Since the Oct 14 disruption, a lot of work and money have gone into rectifying the defects identified. That is commendable. But commuters still have to bear the inconvenience of early closures and late openings on the East-West Line, and full Sunday closures at some stations till May. It is thus important that a strong signal be sent to those found to be responsible for the failures.