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Suica

Puyuma Express derailment

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Suica

An TRA Puyuma Express TEMU2000 series train carrying over 350 passengers has derailed near Xinma station in Taiwan's Yilan County this afternoon.

Over a dozen people were killed. Rescue operations are still ongoing as of now.

Edited by Suica
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Yavianice

Wonder what happened. Looks quite catastrophic.

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Socimi

The most probable cause could be overspeeding, judging from the position of the derailed cars, as the first ones are rolled on their left side.  Also it's a rather sharply curved station.

 

These TEMU2000 series are tilting trains, meaning that they can run in cuvers at a speed higher than normal trains (in fact their maximal commerical speed is 150Km/h on 1067mm narrow gauge tracks).

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Yavianice

Overspeed, as shown in video that captured the crash

 

 

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Suica

This video shows driver's view footage of how fast the train usually goes through this curve and compares the two.

If the CCTV footage is in real time, that's really quite a lot faster.

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Socimi

If i recall correctly the TRA main lines should be equipped with their own saftey system wich is a mix of japanese-style ATS as Taiwan used to be part of Japan until 1945 (they also use shinsha kanko, hear at 0:58 of the above video), and english-style AWS as electrification and signalling upgrades were done in the mid-1970s by a british consortium led by BREL (at 0.14 you can actually hear the AWS "caution" alarm and the "reset" button pressed immediatly after).

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Yavianice

A design flaw has been discovered in the TEMU trains. Apparently, the driver has disabled the speed limiter earlier in the journey, and forgot to turn it back on because he was too busy talking with his supervisors. But, there is no notification or alert that the speed limiter has been disabled. Now my question is, how can someone be so involved in talking that he is not looking out the window, realizing he goes wayy too fast in a curve that he (presumably) drives every day?

 

https://www.reuters.com/article/us-taiwan-accident-nippon-sharyo/japanese-maker-of-train-in-deadly-taiwan-crash-finds-design-flaw-idUSKCN1N702T

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bikkuri bahn

If that is the case, then it’s professional neglect- even if the ATP system was cut, the driver should have maintained safe speed using route knowledge, lineside speed markers, and monitoring the speedometer.  That a train could run at regular line speed without some ATC/ATS activated would be unthinkable in Japan- if an ATC system is cut, the train cannot move faster than 20 km/h (I believe) and then must be reset to resume normal running.  I suppose Taiwan Railways had specified a different operating protocol with these trains. 

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Suica
26 minutes ago, bikkuri bahn said:

I suppose Taiwan Railways had specified a different operating protocol with these trains. 

The driver's remarks make it sound like they rather have not much of an protocol at all.

Switching off a safety feature because something's clearly wrong with the train? What is this? When there's something wrong, a safety feature is the last thing you want to turn off. 

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kvp
3 hours ago, Suica said:

The driver's remarks make it sound like they rather have not much of an protocol at all.

Switching off a safety feature because something's clearly wrong with the train? What is this? When there's something wrong, a safety feature is the last thing you want to turn off. 

Actually i think the only problem with the train's speed could have been that it was running late and the driver and the control center decided to allow it to overspeed on a previous stretch of track to catch up time, then the driver forgot to turn the speed limiter back. The design flaw is that this is allowed at all. (sounds like a system integration problem)

 

A few years back a similar bug was found in the Siemens taurus locomotives, that if the driver switched to shunting mode and then back to line mode, without a restart, the information from the ATS system was ignored. This was a known bug but locomotive drivers tended to abuse it to get out faster from failed blocks that went dark which counts as an all red as a failsafe so it went unreported. The accident that revealed it was when a block fell dark due to system failiure and the preceeding train slowed down to the maximal allowed 15 km/h to get to the next station, while the one with the taurus stopped when the safety system detected a train in the block (hungarian ATS is designed with active train loops so locomotives in the same block could see each other or any stray cars even if the ground system fails, this include rail breaks or intentionally shorted tracks). The driver disabled the ATS with the shunting mode without stopping, then proceeded at line speed and rear ended the train that was going at the maximal allowed speed. This bug was fixed by Siemens by requiring and if ignored triggering a full stop before entering or exiting shunting mode, so the system could enable and disable the ATS properly. Sadly similar errors pop up from time to time and if abused by the drivers could result in accidents.

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Socimi

It's also possible that the ATP was switched off by the driver because it "missed" one or more balises.

 

On "point"-based systems (those who use inductive balises to transmit data such as the Italian SCMT, German INDUSI or British ATP as opposed to "continuous systems" that use the rails themselves), the balises transmits, besides standard line info such as speed limits and signal aspects, the distance to the next balise; meaning that the onboard system (given the train actual speed) knows where and when it will read another balise.

 

If said balise is "missed" (not read/"absence of code"), and it mostly happens due to bad wather or interferences, the system triggers a "locking" emergency braking (like when a signal is passed at danger, e.g. to proceed you've to reset the whole system, as opposed to an emergency braking due to overspeed, where you can relase the brakes by pressing the "vigilance" button or pedal as soon as you get below the speed limit).

 

Italian drivers, when the SCMT misses a balise, after the train has stopped, have to switch off and then switch on again the system (otherwise they wont move) before departing, altough the system can activate itself automatically whenever it passes on a balise. They also are required to call the control center to say wich balise they've missed (wich is automatically informed of any emergency brake activation).

 

The SCMT is actually on all the time (it automatically starts up when the main circuit breaker is closed or the diesel engine started), but it can be set to "Shunting Mode" where it ignores balises (but still won't allow the vehicle to run faster than 30Km/h).

 

The fault in the Tawanese system, is essentially, permitting a complete shut-off of the ATP system and allowing the train to run at line speed at the same time.

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