5 ms·

What are the some of the ways that tracks are monitored for fractures like this? It must have been pretty substantial in order to be described as "complete lac

What are the some of the ways that tracks are monitored for fractures like this? It must have been pretty substantial in order to be described as "complete lack of continuity". Makes me think of literally electronic continuity tests -- are those ever used in this context? Or how about cameras mounted on trains using image processing? Or drones? It seems a shame that a few other trains passed beforehand with this anomaly in place and yet it went undetected.

sigwinch28 9mo ago
Measurement trains filled with cameras and LIDAR For example, in the U.K.: https://en.wikipedia.org/wiki/New_Measurement_Train https://en.wikipedia.org/wiki/New_Measurement_Train
- user_7832 9mo ago
  LIDAR is good, but as another commenter pointed out, Ultrasonic Flaw Detection (USFD) is the gold standard for crack/flaw detection.
- jen729w 9mo ago
  https://en.wikipedia.org/wiki/Doctor_Yellow https://en.wikipedia.org/wiki/Doctor_Yellow
amelius 9mo ago
There are special trains with measurement equipment on board, but yes, it sounds to me like every train should be equipped with some basic sensors for anomaly detection.
- 1718627440 9mo ago
  The measurement trains drive slowly in the night.
  - Azrael3000 9mo ago
    Not necessarily, the measurement train my company develops can go up to 100 km/h and measure certain rail features every 5mm at that speed.
    - lefra 9mo ago
      100 km/h is slow compared to passenger train (even non-high-speed ones). Depending on how packed the schedule is, it might not be possible to analyse track during the day without causing backups.
  - mkl 9mo ago
    They can go at high speed: Germany: https://de.wikipedia.org/wiki/RAILab https://de.wikipedia.org/wiki/RAILab Japan: https://en.wikipedia.org/wiki/Doctor_Yellow https://en.wikipedia.org/wiki/Doctor_Yellow France: https://en.wikipedia.org/wiki/SNCF_TGV_Iris_320 https://en.wikipedia.org/wiki/SNCF_TGV_Iris_320 China: https://en.wikipedia.org/wiki/China_railways_CIT_trains https://en.wikipedia.org/wiki/China_railways_CIT_trains UK: https://en.wikipedia.org/wiki/New_Measurement_Train https://en.wikipedia.org/wiki/New_Measurement_Train
    - mitthrowaway2 9mo ago
      Indeed! > Line inspection is carried out at full speed, up to 270 km/h or 168 mph on the Tōkaidō Shinkansen and 285 km/h or 177 mph on the Sanyō Shinkansen
    - N19PEDL2 9mo ago
      Italy: https://decode39.com/3045/diamond-fs-diagnostics-train-luigi-ferraris/ https://decode39.com/3045/diamond-fs-diagnostics-train-luigi...
gambutin 9mo ago
AFAIK, one technique for monitoring cracks uses ultrasonic sensors. They send sound waves through the rails and detect cracks by analyzing reflected waves.
direwolf20 9mo ago
TFA indicates a 40cm gap — huge!
- buildbot 9mo ago
  I suppose that counts/was caused by a fracture but almost a half meter of gap in the track is nuts. Like describing a limb that’s totally removed as a bone fracture. Though conceivably the break was very small and a train impacting the slightly lifted rail just caused a good chunk of it to explode.
  - WarOnPrivacy 9mo ago
    > Though conceivably the break was very small and a train impacting the slightly lifted rail just caused a good chunk of it to explode. The crown (top) of the rail seems to be missing after the gap. The crown-less section then continues ~3 meters before it disappears behind the investigator on the left. IDK what that might indicate. ref pic: https://ichef.bbci.co.uk/news/1024/cpsprodpb/ecb4/live/53924030-f86e-11f0-9796-05e6aeca39b2.jpg https://ichef.bbci.co.uk/news/1024/cpsprodpb/ecb4/live/53924...
    - zidel 9mo ago
      The rail is laying on its side in that picture, so what is visible is the foot not the web. edit: other angles of the same location here: https://youtu.be/DIQ4SrGSua0?t=1174 https://youtu.be/DIQ4SrGSua0?t=1174
      - WarOnPrivacy 9mo ago
        > The rail is laying on its side in that picture Ah, I see it now. The marks from contact with the ties should have clued me in earlier.
  - kgwgk 9mo ago
    Yes, the “fracture” (the problem was actually at a joint) was there for a while. The missing segment of rail was still there when the train arrived - the derailment affected only the last cars.
djoldman 9mo ago
Wheel Impact Load Detector. It measures vertical forces in kips - (kilo-pounds-force, 1 KIP = 1,000 lbs) They have these in the USA.
- iggldiggl 9mo ago
  Those are for the opposite problem – detecting defective trains (overweight respectively otherwise faulty weight distribution as well as wheel flats).
dkbrk 9mo ago
You can look at the Wikipedia page on railway defect dectectors [0]. Under "rail break monitors" it mentions both electrical continuity and time-domain reflectometry can be used, and are most frequently used on high-speed tracks. In addition, there are vast array of other detectors using acoustic sensors, strain gauges, accelerometers, cameras in the visible and infrared spectrum or laser measurement, that potentially could have detected an anomaly (i.e. damage to the wheels of other trains before the incident). [0]: https://en.wikipedia.org/w/index.php?title=Defect_detector https://en.wikipedia.org/w/index.php?title=Defect_detector
NamTaf 9mo ago
Wheel impacts are the main way. But hardware can be bulky and trains can be surprisingly cramped. We squeezed some track condition monitoring hardware into some locos but it was single-driver operations locations and we cannibalised some of the room that would have otherwise been occupied by the second driver.

sigwinch28 9mo ago

Measurement trains filled with cameras and LIDAR For example, in the U.K.: https://en.wikipedia.org/wiki/New_Measurement_Train https://en.wikipedia.org/wiki/New_Measurement_Train

user_7832 9mo ago
LIDAR is good, but as another commenter pointed out, Ultrasonic Flaw Detection (USFD) is the gold standard for crack/flaw detection.
jen729w 9mo ago
https://en.wikipedia.org/wiki/Doctor_Yellow https://en.wikipedia.org/wiki/Doctor_Yellow

amelius 9mo ago

There are special trains with measurement equipment on board, but yes, it sounds to me like every train should be equipped with some basic sensors for anomaly detection.

1718627440 9mo ago
The measurement trains drive slowly in the night.
- Azrael3000 9mo ago
  Not necessarily, the measurement train my company develops can go up to 100 km/h and measure certain rail features every 5mm at that speed.
  - lefra 9mo ago
    100 km/h is slow compared to passenger train (even non-high-speed ones). Depending on how packed the schedule is, it might not be possible to analyse track during the day without causing backups.
- mkl 9mo ago
  They can go at high speed: Germany: https://de.wikipedia.org/wiki/RAILab https://de.wikipedia.org/wiki/RAILab Japan: https://en.wikipedia.org/wiki/Doctor_Yellow https://en.wikipedia.org/wiki/Doctor_Yellow France: https://en.wikipedia.org/wiki/SNCF_TGV_Iris_320 https://en.wikipedia.org/wiki/SNCF_TGV_Iris_320 China: https://en.wikipedia.org/wiki/China_railways_CIT_trains https://en.wikipedia.org/wiki/China_railways_CIT_trains UK: https://en.wikipedia.org/wiki/New_Measurement_Train https://en.wikipedia.org/wiki/New_Measurement_Train
  - mitthrowaway2 9mo ago
    Indeed! > Line inspection is carried out at full speed, up to 270 km/h or 168 mph on the Tōkaidō Shinkansen and 285 km/h or 177 mph on the Sanyō Shinkansen
  - N19PEDL2 9mo ago
    Italy: https://decode39.com/3045/diamond-fs-diagnostics-train-luigi-ferraris/ https://decode39.com/3045/diamond-fs-diagnostics-train-luigi...

gambutin 9mo ago

AFAIK, one technique for monitoring cracks uses ultrasonic sensors. They send sound waves through the rails and detect cracks by analyzing reflected waves.

direwolf20 9mo ago

TFA indicates a 40cm gap — huge!

buildbot 9mo ago
I suppose that counts/was caused by a fracture but almost a half meter of gap in the track is nuts. Like describing a limb that’s totally removed as a bone fracture. Though conceivably the break was very small and a train impacting the slightly lifted rail just caused a good chunk of it to explode.
- WarOnPrivacy 9mo ago
  > Though conceivably the break was very small and a train impacting the slightly lifted rail just caused a good chunk of it to explode. The crown (top) of the rail seems to be missing after the gap. The crown-less section then continues ~3 meters before it disappears behind the investigator on the left. IDK what that might indicate. ref pic: https://ichef.bbci.co.uk/news/1024/cpsprodpb/ecb4/live/53924030-f86e-11f0-9796-05e6aeca39b2.jpg https://ichef.bbci.co.uk/news/1024/cpsprodpb/ecb4/live/53924...
  - zidel 9mo ago
    The rail is laying on its side in that picture, so what is visible is the foot not the web. edit: other angles of the same location here: https://youtu.be/DIQ4SrGSua0?t=1174 https://youtu.be/DIQ4SrGSua0?t=1174
    - WarOnPrivacy 9mo ago
      > The rail is laying on its side in that picture Ah, I see it now. The marks from contact with the ties should have clued me in earlier.
- kgwgk 9mo ago
  Yes, the “fracture” (the problem was actually at a joint) was there for a while. The missing segment of rail was still there when the train arrived - the derailment affected only the last cars.

djoldman 9mo ago

Wheel Impact Load Detector. It measures vertical forces in kips - (kilo-pounds-force, 1 KIP = 1,000 lbs) They have these in the USA.

iggldiggl 9mo ago
Those are for the opposite problem – detecting defective trains (overweight respectively otherwise faulty weight distribution as well as wheel flats).

dkbrk 9mo ago

You can look at the Wikipedia page on railway defect dectectors [0]. Under "rail break monitors" it mentions both electrical continuity and time-domain reflectometry can be used, and are most frequently used on high-speed tracks. In addition, there are vast array of other detectors using acoustic sensors, strain gauges, accelerometers, cameras in the visible and infrared spectrum or laser measurement, that potentially could have detected an anomaly (i.e. damage to the wheels of other trains before the incident). [0]: https://en.wikipedia.org/w/index.php?title=Defect_detector https://en.wikipedia.org/w/index.php?title=Defect_detector

NamTaf 9mo ago

Wheel impacts are the main way. But hardware can be bulky and trains can be surprisingly cramped. We squeezed some track condition monitoring hardware into some locos but it was single-driver operations locations and we cannibalised some of the room that would have otherwise been occupied by the second driver.