LTA’s explanation raises more questions than answers

LTA’s latest statement raises more questions than it answers. We learned that the two “protective bubbles” around the train both went down long before it was hit. These protective bubbles are critical safety features that alert nearby trains to stop, so as to avoid collisions. Here are 8 questions I would like to ask.

LTA’s latest statement, Investigation Findings on Train Collision at Joo Koon MRT Station, raises more questions than it answers (but good work by the civil servants and SMRT/Thales engineers who put it together). We learned that the two “protective bubbles” around the train both went down long before it was hit. These protective bubbles are critical safety features that alert nearby trains to stop, so as to avoid collisions. LTA’s graphic (part 2) indicates that the first protective bubble went down as soon as the train left Ulu Pandan depot (located between Jurong East and Clementi) due to an “abnormal condition.” Then it was “unexpectedly disabled” when it passed by a “trackside device” at Clementi (while heading east towards Pasir Ris).

1. What caused the protective bubbles go down? What are these trackside devices? Why are they permitted to disable a critical safety feature on a train? And what was the “abnormal condition” that caused the first bubble to go down?

2. Once the second bubble went down, by design an 18 km/h speed restriction was imposed by the new signalling system, which was operating in passive mode. But LTA said the train continued to travel under the old signalling system. So was the 18 km/h speed restriction ignored?

3. Why wasn’t the train automatically brought to a stop or slowed down when the protective bubbles went down? Was an alarm triggered to the Ops Centre?

4. Why did the train continue travelling for almost 2 hours (49 stations) from Clementi to Pasir Ris and back to Pioneer before the driver noticed something was amiss?

5. The NEL and DTL are driverless, unlike the EWL. What happens if the protective bubble goes down on those trains?

6. How many times has this protective bubble gone down without anyone noticing and the trains continued operating? The statement said that the new signalling system runs in the background in passive mode between Pioneer and Pasir Ris to “collect data for the purpose of performance monitoring.” So there should be logs to trace back the answer. If the answer is “it has gone down many times”, then this accident was not “bad luck”, but it was “good luck” that there weren’t more accidents earlier on.

7. Once the train arrived at Joo Koon and was de-training all its passengers, why was the next train allowed to come within 36 m, if the stationary train’s protective bubble was gone? A train approaching the platform at 50 km/h will take less than 2.6 sec to cover 36 m. Is it SOP for trains to get so close before stopping?

8. Lastly, did anyone tell the driver of the train behind that the train ahead had no protective bubble? Evidently not, because he didn’t think anything was amiss and therefore did not react in time when he realised the train was lurching forward.

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1 thought on “LTA’s explanation raises more questions than answers”

  1. I think a more pertinent question is why the trains don’t have proximity sensors built into the train head/tail themselves. Like how modern cars have reverse sensors.

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