5 ms·

A new way of keeping trains apart uses magnetic signals in the tracks

ColinWright 4y ago
https://web.archive.org/web/20221001114657/https://www.economist.com/science-and-technology/2022/09/28/keeping-trains-apart-is-crucial-to-safety https://web.archive.org/web/20221001114657/https://www.econo...
smileysteve 4y ago
The difficulties with gps seem over stated, Which Track? Trains don't randomly switch tracks except in yards, instrumenting each switch to understand when a train switches tracks seems like an easy problem. Tunnels? First there aren't "that" many and there aren't many long enough that a single long train shouldn't count it as occupied in the interest of safety. It also shouldn't be a high effort to add a satellite or wireless repeater with a known location at at least each end of a tunnel. An arduino with GPS tracking an accelerometer (or gyro), a compass, add a few wireless location nodes around tunnels and other dead spots and every difficulty here is solved. The accelerometer can even early report rough tracks or switches. What excuses the economist entertains while we have successful tracking in many other forms of transport.
- matthewmacleod 4y ago
  Of course, in reality you can't build safety-critical systems that operate in challenging rail environments by slapping together an Arduino, a GPS receiver, and an IMU and saying "problem solved lol". None of the things you have described are "easy problems". In fact, they are pretty difficult! Systems need to be robust, interoperable, reliable, provably correct, fail safely, deal with surprising edge cases, have long service lives, and any number of other challenges. In any case, all you've really done here is re-invent technology that already exists. In ETCS level 2, for example, the signalling system uses known-location transmitters on the track as references and the train calculates its position in-between using on-board sensors like axle encoders, IMUs etc. This is just a short article about an interesting new technology for providing the "train position" component of the system by building a magnetic map of the rails. Pretty cool idea – if it's accurate enough, it provides a more robust source of absolute positioning information, which is key to allowing the rollout of realising "moving-block" approaches in which trains' movement authorities are updated in real-time, allowing higher traffic density. And it's not like nobody's thought about GPS/GNSS either – there have been extensive projects looking into the feasibility of those systems. The Russian ABTC-M system uses GLONASS, and I'm sure some implementations of PTC in the US use GPS. But again, these are difficult challenges incorporating lots of different technology and you don't solve them overnight.
  - sitkack 4y ago
    They should be solved asap. Increasing rail utilization is key to many of the problems we are facing. Rail can move cities, nothing else can do that. Many of these things would be solvable by solar powered cameras on 4G/5G/starlink. Vibration sensors in the tracks, transponders in the cars, wheels, engines, etc. We need way more signals than we currently have.
    - bobthepanda 4y ago
      Generally speaking, LIDAR or cameras on trains don’t solve much, because trains’ braking distances (and therefore what they need to “see”) extends for hundreds of meters, sometimes over a kilometer, and around curves, walls, etc. It’s a different problem space. Rail utilization will certainly help at the margins, but only maybe one or two trains an hour. The real meat and potatoes is generally more tracks, and removing conflict points on existing ones.
      - sitkack 4y ago
        You can dead reckon speed, location from camera lidar data, just like what they were doing with the magnetic map in the article. I made no statements that the train would be locally self engineering using the cameras.
        bobthepanda 4y ago
        If dead reckoning is what you're relying on, you need * the last junction you passed and how you exited, and * number of turns of the wheel. The issue is that rewiring junctions is very expensive, upgrading trains to be compatible is expensive, etc. Even more so if you cannot upgrade an entire network all at once, and you need to account for mixed operations with both new and legacy compatible systems.
      - kposehn 4y ago
        Lidar on trains has some uses, but you're quite correct that it isn't the primary sensor. However, automating trains on heavy-haul networks like the US & Brazil is a big opportunity. The pressure to reduce crew costs means longer trains and less network fluidity; automating them allows much shorter point-to-point consists on the same infrastructure. As long as they have the right sensors they can run much closer together - even couple & de-couple en route (with some extra equipment).
- KaiserPro 4y ago
  > Which Track? Trains don't randomly switch tracks except in yards, Track spacing is often much less than the dilution of position, which is less than ideal. This means that the area that the GPS thinks the train is, is bigger than the track width. Trains in the UK are often in cuttings, urban canyons etc, which means that the error margin could be up to 100m without much effort. > instrumenting each switch to understand when a train switches tracks seems like an easy problem. Only if you ignore that those sensors are now life critical, so is the connection, and the software that joins it all up. > Tunnels? First there aren't "that" many and there aren't many long enough that a single long train shouldn't count it as occupied in the interest of safety. again see DoP. But safety distance is related to speed. the slower the trains the shorter the distance, which means you are more likley to bump into GPS DoP issues. Also tunnels normally have cuttings, which again limit the number of satellites visible. > It also shouldn't be a high effort to add a satellite or wireless repeater with a known location at at least each end of a tunnel. again see safety critical equipment, you'll need fail safes > The accelerometer can even early report rough tracks or switches. Whats the percentage drift per second of those sensors? How often is the calibration frequency? how much vibration can it handle before it becomes inaccurate? whats the mean time to failure? As a point, the "new" thameslink trains refused to open its doors at the thameslink station, because the station was in a tunnel, and the GPS wasn't available. This meant that the train said it didn't know where it was, so no doors open. As a general rule of thumb, life critical stuff needs to be simple, well tested and well characterised. Failure of a system might cause a death, subtle failure is even more dangerous. This means expense.
  - smileysteve 4y ago
    > Track spacing is often much less than the dilution of position, Which is why I spell out to instrument the current reporting switches (which are the current systems (and yes they fail)) > As a general rule of thumb, life critical stuff needs to be simple, well tested and well characterised. For context, my state leads in railroad crossing deaths, in part because the existing signaling infrastructure is too sparse or dilapidated. >
- Animats 4y ago
  > The difficulties with GPS seem over stated. If anything, they are understated. GPS is so easy to spoof that it should not be used in a vital system. Most train control systems have two completely separate systems. One keeps trains from running into each other, and the other makes the railroad run efficiently. The first usually depends on brutally simple and fail-safe wayside equipment. The second is based on direction from a control center somewhere. The second system is capable of keeping trains separated on its own, and it's so tempting to get rid of all that wayside safety equipment, with all that gear in trackside boxes needing maintenance visits.
- NamTaf 4y ago
  This is hilariously hand-wavey of the complexity and strikes at my frustrations between how most IT engineers see the world vs how real-world engineers do. There are parallel tracks within metres of one another. Switching yards have tonnes of them and require precise knowledge of what’s in what. GPS isn’t SIL. Trains operate in cluttered environments with reflection and echo abound. That causes drift above the separation of tracks. There’s way more than “a few” dead spots, and what happens if those repeaters fall over? There’s tonnes of reasons why high tech isn’t used in train safety-critical systems. The fact you suggest an arduino as an appropriate platform for this is frankly absurd and underscores your misunderstanding of the whole issue. Close enough isn’t good enough. Crashing doesn’t just mean you reboot or reload the program and try again. It means people die. Edit to add: A good rule of thumb I’ve learnt after 15 years in the game: if you look at the solution to an engineering problem and then start a sentence with “why don’t they just…”, you probably don’t understand the problem well enough.
  - olivermuty 4y ago
    To be fair, «why don’t they just» has also made a lot of startup founders very wealthy over the last 15 years ;)
    - NamTaf 4y ago
      I’ll cop that, though I’m fairly confident in saying it’s the exception that proves the rule, in that those ones end up knowing the problem space so well that they sort of horseshoe around to seeing new insights others miss.
      - bobthepanda 4y ago
        also, even though some startup founders have become very rich questioning the basics with technology, many more have failed.
  - jen729w 4y ago
    > how most IT engineers see the world vs how real-world engineers do Reminds me of… # Programmers: Stop Calling Yourselves Engineers “It undermines a long tradition of designing and building infrastructure in the public interest … The title ‘engineer’ is cheapened by the tech industry.” https://www.theatlantic.com/technology/archive/2015/11/programmers-should-not-call-themselves-engineers/414271/ https://www.theatlantic.com/technology/archive/2015/11/progr...
pestatije 4y ago
Now i can imagine some rail being reused for a different line and suddenly trains showing up in the old line on screens in the control room.
- AnimalMuppet 4y ago
  It might be worse than that. Rail wears, so the signature probably changes with time, even if nobody moves the rail. Then, in the US, they sometimes use "rail grinders" - specialized trains that literally grind the surface of the rail, in order to remove things like spalling that come from heavy use. That probably changes the magnetic signature, too, a lot faster than regular wear does. That's not insoluble - re-map after you grind. But it does complicate things somewhat.
deleted 4y ago
[deleted]
ChildOfChaos 4y ago
Well i'd imagine when they touch, that's kinda bad for safety...
msbarnett 4y ago
> For a 200-metre section, Dr Lauer calculates, there is about one chance in a trillion that it is duplicated anywhere on the 2.3bn kilometres of track currently laid around the world. Uh, isn’t this the wrong calculation though? We don’t care about the chance of collision between a particular section and any other section, we care about the chance that any pair of sections collide. Birthday paradox stuff.
- teraflop 4y ago
  I don't think the birthday paradox is exactly the right model either. By itself, a matching fingerprint between two different rail sections on opposite sides of the world wouldn't present a problem, as long as the train knows its initial location and is smart enough to know it couldn't have instantly teleported. You just need a low enough probability of collisions between nearby pairs of track segments in order to not get lost. But in any case, the statement you quotes smells like very sloppy statistics. There's a huge difference between saying that the pattern of permeability is unpredictable, and saying it's random -- the latter is a very strong assumption. It's easy to imagine ways the measurement could have local or global biases towards particular kinds of patterns, and the existence of any such effects would make the "one in a trillion" number completely meaningless. On top of that, the article says magnetic permeability isn't part of the official material specifications. What happens if the railroad operator switches to a new supplier, whose process results in rails that are much more uniform? This seems to be the research group's web page: https://www.mrt.kit.edu/disensor/ https://www.mrt.kit.edu/disensor/ I looked for a published paper that would go into more detail, but I couldn't find one.
  - uup 4y ago
    If there were biases, then the pattern of permeability would be predictable. For instance, encrypted data is not random, but it's not predictable.
- sudhirj 4y ago
  The birthday paradox has a factor for the number of people in the room - the question isn’t usually who else has the same birthday in the entire universe, it’s who else within loud talking distance. Here restricting the search to a radius of known starting positions should suffice.
bombcar 4y ago
The title reminds me of https://en.m.wikipedia.org/wiki/How_to_Avoid_Huge_Ships https://en.m.wikipedia.org/wiki/How_to_Avoid_Huge_Ships
- kfarr 4y ago
  Title has since changed but originally it was something like "trains should not be on the same track to avoid collisions"
Stevvo 4y ago
Sounds really complex. Why not just count how many times the wheels turn?
- FredPret 4y ago
  Train wheels spin. It’s steel on steel
- NamTaf 4y ago
  Wheels slip and their diameter changes which throws out dead reckoning. Counters are also not accurate and will have cumulative error over time. It’s complex because edge cases like this exist for simpler systems.
  - kevincox 4y ago
    > their diameter changes To be clear they are not cylinders, but cones (truncated). Do depending on how the train wobbles they will spin differently to travel the same distance even if they don't slip. So you definitely need some method of regular correction if you want accurate measurements.
    - NamTaf 4y ago
      I in fact meant that they wear through quite substantial diameter differences, but yes conical tread will further throw it out.
lowbloodsugar 4y ago
The economist is playing Factorio now.
pstuart 4y ago
tl;dr -- fingerprint the magnetic properties of the rails themselves and map accordingly. This is incredibly clever and I hope this catches on.
lb1lf 4y ago
Just after two trains had crashed at Åsta in Norway back in 2000 or so, a journalist from the Norwegian Broadcasting Company managed to ask the accident site manager whether the trains had been on the same track when they collided. Long, crushing silence, then. "Presumably, yes." If I remember correctly, one of the key findings after the accident was that train controllers' only means of communicating with the trains they were supervising was to call the train drivers. On their personal cell phones. It was part of the procedure prior to starting a journey to call in to the central and have the controllers write down the phone number to be used to reach, say, the southbound from Trondheim. Now we luckily have modern train management systems and GSM-R, but 19 people died at Åsta because the northbound driver seemingly forgot that there was a southbound train on incoming on the track he was going to use - and didn't pay attention to the signal telling him the track was occupied. Then, once the northbound train got going, train control took a couple of minutes to figure out what had happened and then also found out that he couldn't find the note with today's phone numbers.
- AnimalMuppet 4y ago
  Wow. That's kind of crazy. Seems like the main failure was the northbound running the signal, though. The lack of radio just means that they had no way to save the situation after the mistake happened.
  - lb1lf 4y ago
    Nowadays, the train controller can stop a train remotely even if unable to raise the train on the radio. Still baffles me how packed the old system was with failure modes, though.
    - NamTaf 4y ago
      What system do they use for this? I’m not aware of any remote-stop functionality outside of driverless railways but that’s not to say it doesn’t exist.
      - 4y ago
just_boost_it 4y ago
This is a pretty cool idea. Trains make a surprising amount of money, so there's probably a lot of money to be made if it increases efficiency. The costs of errors here are measured in lives though, not Jira tickets, so I hope he's done some very careful testing.
- NamTaf 4y ago
  I tend to agree that it’s a nifty idea but I think it’s a decade or so too late as the industry settles on ETCS. The legwork to prove ETCS as SIL-rated is done, whereas this has all those uphill battles still to fight and I’m not sure it’ll have the potential advantages to overcome that. You can also approach any of the Siemens/Hitachi/Bombardier/etcs. of the world and have no issue spec’ing for ETCS today. This does have potential advantages in maybe finding track defects if set up correctly to do so? But that sort of system already exists and is installed on rolling stock, so once again it’s having to overcome the first mover advantage.
mikewarot 4y ago
It's a cute, but impractical idea. It requires materials not to change properties over time, track not to wear, a globally distributed map that is always up to date and consistent.
- blix 4y ago
  Each train would have a sensor which would be able to detect changes and update the database. Maps could easily be regional.
  - mikewarot 4y ago
    If you can update with changes on the fly, then you can propagate errors on the fly as well. There are likely some quite fatal corner cases that could be found the hard way.
    - blix 4y ago
      It's a good thing we aren't using updated updated-on-the-fly computer systems for controlling powerplants, chemical refineries, trading on finacial markets or driving cars!
      - mikewarot 4y ago
        Knight Capital updated their your stock algorithms on the fly, instead of properly investigating the cause of failure[1], resulting in a loss of USD$460 Million after unwinding most of the trades with other firms. [1] https://en.wikipedia.org/wiki/Knight_Capital_Group https://en.wikipedia.org/wiki/Knight_Capital_Group
- pstuart 4y ago
  If the properties are consistent enough, and it's inexpensive to update then it seems not unreasonable at all. They certainly seem to think so.
- deleted 4y ago
  [deleted]
deleted 4y ago
[deleted]
foverzar 4y ago
"New"? What's so new about what seems to be like a common Automatic block signaling? I thought that this was a commonly used thing. Hence a small current on the rails (you can even tap into it and charge your phone).

https://web.archive.org/web/20221001114657/https://www.economist.com/science-and-technology/2022/09/28/keeping-trains-apart-is-crucial-to-safety https://web.archive.org/web/20221001114657/https://www.econo...

smileysteve 4y ago

The difficulties with gps seem over stated, Which Track? Trains don't randomly switch tracks except in yards, instrumenting each switch to understand when a train switches tracks seems like an easy problem. Tunnels? First there aren't "that" many and there aren't many long enough that a single long train shouldn't count it as occupied in the interest of safety. It also shouldn't be a high effort to add a satellite or wireless repeater with a known location at at least each end of a tunnel. An arduino with GPS tracking an accelerometer (or gyro), a compass, add a few wireless location nodes around tunnels and other dead spots and every difficulty here is solved. The accelerometer can even early report rough tracks or switches. What excuses the economist entertains while we have successful tracking in many other forms of transport.

matthewmacleod 4y ago
Of course, in reality you can't build safety-critical systems that operate in challenging rail environments by slapping together an Arduino, a GPS receiver, and an IMU and saying "problem solved lol". None of the things you have described are "easy problems". In fact, they are pretty difficult! Systems need to be robust, interoperable, reliable, provably correct, fail safely, deal with surprising edge cases, have long service lives, and any number of other challenges. In any case, all you've really done here is re-invent technology that already exists. In ETCS level 2, for example, the signalling system uses known-location transmitters on the track as references and the train calculates its position in-between using on-board sensors like axle encoders, IMUs etc. This is just a short article about an interesting new technology for providing the "train position" component of the system by building a magnetic map of the rails. Pretty cool idea – if it's accurate enough, it provides a more robust source of absolute positioning information, which is key to allowing the rollout of realising "moving-block" approaches in which trains' movement authorities are updated in real-time, allowing higher traffic density. And it's not like nobody's thought about GPS/GNSS either – there have been extensive projects looking into the feasibility of those systems. The Russian ABTC-M system uses GLONASS, and I'm sure some implementations of PTC in the US use GPS. But again, these are difficult challenges incorporating lots of different technology and you don't solve them overnight.
- sitkack 4y ago
  They should be solved asap. Increasing rail utilization is key to many of the problems we are facing. Rail can move cities, nothing else can do that. Many of these things would be solvable by solar powered cameras on 4G/5G/starlink. Vibration sensors in the tracks, transponders in the cars, wheels, engines, etc. We need way more signals than we currently have.
  - bobthepanda 4y ago
    Generally speaking, LIDAR or cameras on trains don’t solve much, because trains’ braking distances (and therefore what they need to “see”) extends for hundreds of meters, sometimes over a kilometer, and around curves, walls, etc. It’s a different problem space. Rail utilization will certainly help at the margins, but only maybe one or two trains an hour. The real meat and potatoes is generally more tracks, and removing conflict points on existing ones.
    - sitkack 4y ago
      You can dead reckon speed, location from camera lidar data, just like what they were doing with the magnetic map in the article. I made no statements that the train would be locally self engineering using the cameras.
      - bobthepanda 4y ago
        If dead reckoning is what you're relying on, you need * the last junction you passed and how you exited, and * number of turns of the wheel. The issue is that rewiring junctions is very expensive, upgrading trains to be compatible is expensive, etc. Even more so if you cannot upgrade an entire network all at once, and you need to account for mixed operations with both new and legacy compatible systems.
    - kposehn 4y ago
      Lidar on trains has some uses, but you're quite correct that it isn't the primary sensor. However, automating trains on heavy-haul networks like the US & Brazil is a big opportunity. The pressure to reduce crew costs means longer trains and less network fluidity; automating them allows much shorter point-to-point consists on the same infrastructure. As long as they have the right sensors they can run much closer together - even couple & de-couple en route (with some extra equipment).
KaiserPro 4y ago
> Which Track? Trains don't randomly switch tracks except in yards, Track spacing is often much less than the dilution of position, which is less than ideal. This means that the area that the GPS thinks the train is, is bigger than the track width. Trains in the UK are often in cuttings, urban canyons etc, which means that the error margin could be up to 100m without much effort. > instrumenting each switch to understand when a train switches tracks seems like an easy problem. Only if you ignore that those sensors are now life critical, so is the connection, and the software that joins it all up. > Tunnels? First there aren't "that" many and there aren't many long enough that a single long train shouldn't count it as occupied in the interest of safety. again see DoP. But safety distance is related to speed. the slower the trains the shorter the distance, which means you are more likley to bump into GPS DoP issues. Also tunnels normally have cuttings, which again limit the number of satellites visible. > It also shouldn't be a high effort to add a satellite or wireless repeater with a known location at at least each end of a tunnel. again see safety critical equipment, you'll need fail safes > The accelerometer can even early report rough tracks or switches. Whats the percentage drift per second of those sensors? How often is the calibration frequency? how much vibration can it handle before it becomes inaccurate? whats the mean time to failure? As a point, the "new" thameslink trains refused to open its doors at the thameslink station, because the station was in a tunnel, and the GPS wasn't available. This meant that the train said it didn't know where it was, so no doors open. As a general rule of thumb, life critical stuff needs to be simple, well tested and well characterised. Failure of a system might cause a death, subtle failure is even more dangerous. This means expense.
- smileysteve 4y ago
  > Track spacing is often much less than the dilution of position, Which is why I spell out to instrument the current reporting switches (which are the current systems (and yes they fail)) > As a general rule of thumb, life critical stuff needs to be simple, well tested and well characterised. For context, my state leads in railroad crossing deaths, in part because the existing signaling infrastructure is too sparse or dilapidated. >
Animats 4y ago
> The difficulties with GPS seem over stated. If anything, they are understated. GPS is so easy to spoof that it should not be used in a vital system. Most train control systems have two completely separate systems. One keeps trains from running into each other, and the other makes the railroad run efficiently. The first usually depends on brutally simple and fail-safe wayside equipment. The second is based on direction from a control center somewhere. The second system is capable of keeping trains separated on its own, and it's so tempting to get rid of all that wayside safety equipment, with all that gear in trackside boxes needing maintenance visits.
NamTaf 4y ago
This is hilariously hand-wavey of the complexity and strikes at my frustrations between how most IT engineers see the world vs how real-world engineers do. There are parallel tracks within metres of one another. Switching yards have tonnes of them and require precise knowledge of what’s in what. GPS isn’t SIL. Trains operate in cluttered environments with reflection and echo abound. That causes drift above the separation of tracks. There’s way more than “a few” dead spots, and what happens if those repeaters fall over? There’s tonnes of reasons why high tech isn’t used in train safety-critical systems. The fact you suggest an arduino as an appropriate platform for this is frankly absurd and underscores your misunderstanding of the whole issue. Close enough isn’t good enough. Crashing doesn’t just mean you reboot or reload the program and try again. It means people die. Edit to add: A good rule of thumb I’ve learnt after 15 years in the game: if you look at the solution to an engineering problem and then start a sentence with “why don’t they just…”, you probably don’t understand the problem well enough.
- olivermuty 4y ago
  To be fair, «why don’t they just» has also made a lot of startup founders very wealthy over the last 15 years ;)
  - NamTaf 4y ago
    I’ll cop that, though I’m fairly confident in saying it’s the exception that proves the rule, in that those ones end up knowing the problem space so well that they sort of horseshoe around to seeing new insights others miss.
    - bobthepanda 4y ago
      also, even though some startup founders have become very rich questioning the basics with technology, many more have failed.
- jen729w 4y ago
  > how most IT engineers see the world vs how real-world engineers do Reminds me of… # Programmers: Stop Calling Yourselves Engineers “It undermines a long tradition of designing and building infrastructure in the public interest … The title ‘engineer’ is cheapened by the tech industry.” https://www.theatlantic.com/technology/archive/2015/11/programmers-should-not-call-themselves-engineers/414271/ https://www.theatlantic.com/technology/archive/2015/11/progr...

pestatije 4y ago

Now i can imagine some rail being reused for a different line and suddenly trains showing up in the old line on screens in the control room.

AnimalMuppet 4y ago
It might be worse than that. Rail wears, so the signature probably changes with time, even if nobody moves the rail. Then, in the US, they sometimes use "rail grinders" - specialized trains that literally grind the surface of the rail, in order to remove things like spalling that come from heavy use. That probably changes the magnetic signature, too, a lot faster than regular wear does. That's not insoluble - re-map after you grind. But it does complicate things somewhat.

deleted 4y ago

[deleted]

ChildOfChaos 4y ago

Well i'd imagine when they touch, that's kinda bad for safety...

msbarnett 4y ago

> For a 200-metre section, Dr Lauer calculates, there is about one chance in a trillion that it is duplicated anywhere on the 2.3bn kilometres of track currently laid around the world. Uh, isn’t this the wrong calculation though? We don’t care about the chance of collision between a particular section and any other section, we care about the chance that any pair of sections collide. Birthday paradox stuff.

teraflop 4y ago
I don't think the birthday paradox is exactly the right model either. By itself, a matching fingerprint between two different rail sections on opposite sides of the world wouldn't present a problem, as long as the train knows its initial location and is smart enough to know it couldn't have instantly teleported. You just need a low enough probability of collisions between nearby pairs of track segments in order to not get lost. But in any case, the statement you quotes smells like very sloppy statistics. There's a huge difference between saying that the pattern of permeability is unpredictable, and saying it's random -- the latter is a very strong assumption. It's easy to imagine ways the measurement could have local or global biases towards particular kinds of patterns, and the existence of any such effects would make the "one in a trillion" number completely meaningless. On top of that, the article says magnetic permeability isn't part of the official material specifications. What happens if the railroad operator switches to a new supplier, whose process results in rails that are much more uniform? This seems to be the research group's web page: https://www.mrt.kit.edu/disensor/ https://www.mrt.kit.edu/disensor/ I looked for a published paper that would go into more detail, but I couldn't find one.
- uup 4y ago
  If there were biases, then the pattern of permeability would be predictable. For instance, encrypted data is not random, but it's not predictable.
sudhirj 4y ago
The birthday paradox has a factor for the number of people in the room - the question isn’t usually who else has the same birthday in the entire universe, it’s who else within loud talking distance. Here restricting the search to a radius of known starting positions should suffice.

bombcar 4y ago

The title reminds me of https://en.m.wikipedia.org/wiki/How_to_Avoid_Huge_Ships https://en.m.wikipedia.org/wiki/How_to_Avoid_Huge_Ships

kfarr 4y ago
Title has since changed but originally it was something like "trains should not be on the same track to avoid collisions"

Stevvo 4y ago

Sounds really complex. Why not just count how many times the wheels turn?

FredPret 4y ago
Train wheels spin. It’s steel on steel
NamTaf 4y ago
Wheels slip and their diameter changes which throws out dead reckoning. Counters are also not accurate and will have cumulative error over time. It’s complex because edge cases like this exist for simpler systems.
- kevincox 4y ago
  > their diameter changes To be clear they are not cylinders, but cones (truncated). Do depending on how the train wobbles they will spin differently to travel the same distance even if they don't slip. So you definitely need some method of regular correction if you want accurate measurements.
  - NamTaf 4y ago
    I in fact meant that they wear through quite substantial diameter differences, but yes conical tread will further throw it out.

lowbloodsugar 4y ago

The economist is playing Factorio now.

pstuart 4y ago

tl;dr -- fingerprint the magnetic properties of the rails themselves and map accordingly. This is incredibly clever and I hope this catches on.

lb1lf 4y ago

Just after two trains had crashed at Åsta in Norway back in 2000 or so, a journalist from the Norwegian Broadcasting Company managed to ask the accident site manager whether the trains had been on the same track when they collided. Long, crushing silence, then. "Presumably, yes." If I remember correctly, one of the key findings after the accident was that train controllers' only means of communicating with the trains they were supervising was to call the train drivers. On their personal cell phones. It was part of the procedure prior to starting a journey to call in to the central and have the controllers write down the phone number to be used to reach, say, the southbound from Trondheim. Now we luckily have modern train management systems and GSM-R, but 19 people died at Åsta because the northbound driver seemingly forgot that there was a southbound train on incoming on the track he was going to use - and didn't pay attention to the signal telling him the track was occupied. Then, once the northbound train got going, train control took a couple of minutes to figure out what had happened and then also found out that he couldn't find the note with today's phone numbers.

AnimalMuppet 4y ago
Wow. That's kind of crazy. Seems like the main failure was the northbound running the signal, though. The lack of radio just means that they had no way to save the situation after the mistake happened.
- lb1lf 4y ago
  Nowadays, the train controller can stop a train remotely even if unable to raise the train on the radio. Still baffles me how packed the old system was with failure modes, though.
  - NamTaf 4y ago
    What system do they use for this? I’m not aware of any remote-stop functionality outside of driverless railways but that’s not to say it doesn’t exist.
    - 4y ago

just_boost_it 4y ago

This is a pretty cool idea. Trains make a surprising amount of money, so there's probably a lot of money to be made if it increases efficiency. The costs of errors here are measured in lives though, not Jira tickets, so I hope he's done some very careful testing.

NamTaf 4y ago
I tend to agree that it’s a nifty idea but I think it’s a decade or so too late as the industry settles on ETCS. The legwork to prove ETCS as SIL-rated is done, whereas this has all those uphill battles still to fight and I’m not sure it’ll have the potential advantages to overcome that. You can also approach any of the Siemens/Hitachi/Bombardier/etcs. of the world and have no issue spec’ing for ETCS today. This does have potential advantages in maybe finding track defects if set up correctly to do so? But that sort of system already exists and is installed on rolling stock, so once again it’s having to overcome the first mover advantage.

mikewarot 4y ago

It's a cute, but impractical idea. It requires materials not to change properties over time, track not to wear, a globally distributed map that is always up to date and consistent.

blix 4y ago
Each train would have a sensor which would be able to detect changes and update the database. Maps could easily be regional.
- mikewarot 4y ago
  If you can update with changes on the fly, then you can propagate errors on the fly as well. There are likely some quite fatal corner cases that could be found the hard way.
  - blix 4y ago
    It's a good thing we aren't using updated updated-on-the-fly computer systems for controlling powerplants, chemical refineries, trading on finacial markets or driving cars!
    - mikewarot 4y ago
      Knight Capital updated their your stock algorithms on the fly, instead of properly investigating the cause of failure[1], resulting in a loss of USD$460 Million after unwinding most of the trades with other firms. [1] https://en.wikipedia.org/wiki/Knight_Capital_Group https://en.wikipedia.org/wiki/Knight_Capital_Group
pstuart 4y ago
If the properties are consistent enough, and it's inexpensive to update then it seems not unreasonable at all. They certainly seem to think so.
deleted 4y ago
[deleted]

deleted 4y ago

[deleted]

foverzar 4y ago

"New"? What's so new about what seems to be like a common Automatic block signaling? I thought that this was a commonly used thing. Hence a small current on the rails (you can even tap into it and charge your phone).