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Track condition monitoring using passenger mobile phones

Measure rail track condition by collecting accelerometer data from passenger’s mobile phones
  [vote for,

The condition of a railway track is critical to the safety of the trains (and passengers) who travel over it.

Defects in rails tend to develop over time, and if left unnoticed can become catastrophic - cracks and rail breakage do occur, and kinks (vertical or horizontal displacements) can give rise to high accelerations, excessive loads, rollingstock damage or even derailment.

Railway owners spend a great deal on regular human inspection (boots on the ballast), and on expensive rail measurement trains, to identify defects for fixing before they become dangerous.

I travel by train quite a lot, and I notice particular places on my route where the train lurches alarmingly, or clunks heavily... and I wonder whether the track maintenance team have been out to have a look recently.

I also use the train operator’s mobile phone app to buy my tickets, check train times, and check for disruptions.

Given a train full of passengers with mobile phones, each of which has an accelerometer (and GPS) built in, it shouldn’t be difficult to collect acceleration/location data from a large number of devices and extract useful condition data from it.

Each individual phone might have a significant error, but interpolating across the population (ie Kalman filter) should produce reasonable accuracy.

When a passenger signs up to the ticket/disruption app, they’re asked if they’d also contribute (their data) to the reliability and safety of the railway.

Frankx, Sep 14 2019

Network Rail New Measurement Train https://www.youtube...watch?v=WhVdTXh5XoA
Also known as the Flying Banana [Frankx, Sep 14 2019]

Smartphone Sensing Capabilities for On-Board Railway Track Monitoring https://doi.org/10.1155/2019/1729153
André Paixão, Eduardo Fortunato, and Rui Calçada, 2019 [Frankx, Sep 15 2019]


       I like the idea of using cheap consumer accelerometers to monitor track conditions. However, if it worked, wouldn't it be better to take one such accelerometer and mount it rigidly on either the train or the suspension? That would give you more accurate data than the average of a few dozen phones, each one only loosely coupled to the train and all wiggling independently.
MaxwellBuchanan, Sep 14 2019

       //wiggling independently//   


       Yes, true. But for each train you’d have to buy a big rugged “railway-approved” box and bolt it onto an appropriate bit of train structure, and provide a power supply and rugged aerials - all of which gets quite pricey.   

       Whereas your passengers collect the data without even knowing it, with ready-charged and freely communicating phones.   

       I think you can collect the data from them essentially for free, and do some clever signal extraction, to get good data out of the “wiggly” data
Frankx, Sep 14 2019

       But... if the railway is prepared to use passenger data to guide its track maintenance, it could get (and use) the same data much more cleanly using the same equipment.   

       What I mean is - it's probably harder to get a railway to rely on [badly-coupled mobile phones + multiple passengers who move independently] than to get them to rely on [a single well-coupled mobile phone]. If the former worked, the latter would work somewhat better and would be easier to justify.
MaxwellBuchanan, Sep 14 2019

       Also, re. the wiggliness and data averaging.   

       Suppose a typical minor track fault causes a jolt of magnitude 1 to the seated passenger. Suppose also that the movements of a passenger cause jolts (noise) of magnitude 10. If you average 2 passengers, the data will have a noise of about 10 over root2, or around 7. If you average over 10 passengers, you'll have a noise of around 3. If you average over 100 passengers, you'll have a noise of about 1 - and so you still won't be able to detect minor track faults.   

       You might do better if you harvested sound, since many track faults produce a distinctive sound; but passengers will not be happy with having their phones transmit their audio to the rail network.
MaxwellBuchanan, Sep 14 2019

       Hmm. Thanks [MB], i’ll have a look at some figures.
Frankx, Sep 15 2019

       Not needed in places like Japan, where the tracks are engineered to total perfection, allowing their amazing trains to have timekeeping to the second. Would be useful in places like the UK or North America where trains and track technology hasn't advanced from the Victorian era.
xenzag, Sep 15 2019

       Doesn't accelerometer hardware have three axises? to tell what sort of action is being vectored. Shouldn't a train joint stick out in the norm of passengers sitting, standing semi-motionless data? Time referenced with 100 passengers, the waveform should travel through the phones down the train.
wjt, Sep 15 2019

       //won't be able to detect minor track faults//   

       Well, looks like I'll have to learn some of the maths around Kalman filters. I think they can do this - as you point out, error decreases with the number of input sources.   

       Also, the same section of track can be measured by multiple trains, so data can be summed across many passes.   

       For the railway owner, this would be no-cost real-time track data with no requirement for additional boxes/infrastructure.   

       I think that's quite an attractive proposition
Frankx, Sep 15 2019

       ///Not needed in places like Japan, where the tracks are engineered...   

       Ahem, recent shinkansen blunder after a cleaner left the door open, kind of windy inside. And, the whole non-shinkansen train timetable goes to pot late Friday night, due to drunks falling over and getting stuck in the doors etc
not_morrison_rm, Sep 16 2019

       [not_morrison_rm] Personal experience?
wjt, Sep 16 2019

       Safety on the Japanese rail system is comparable with the UK. We have plenty of embarrassing (and alarming) incidents too.
Frankx, Sep 16 2019

       // You might do better if you harvested sound, since many track faults produce a distinctive sound; but passengers will not be happy with having their phones transmit their audio to the rail network. //   

       In Calgary, the train cars have signs on the doors notifying passengers that video and audio recording is going on within. They could use that audio.
notexactly, Sep 26 2019


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