[HN Gopher] A new way of keeping trains apart uses magnetic sign... ___________________________________________________________________ A new way of keeping trains apart uses magnetic signals in the tracks Author : helsinkiandrew Score : 36 points Date : 2022-10-01 11:46 UTC (11 hours ago) (HTM) web link (www.economist.com) (TXT) w3m dump (www.economist.com) | bombcar wrote: | The title reminds me of | https://en.m.wikipedia.org/wiki/How_to_Avoid_Huge_Ships | msbarnett wrote: | > 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 wrote: | 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/ I looked for a published | paper that would go into more detail, but I couldn't find one. | ColinWright wrote: | https://web.archive.org/web/20221001114657/https://www.econo... | [deleted] | Stevvo wrote: | Sounds really complex. | | Why not just count how many times the wheels turn? | FredPret wrote: | Train wheels spin. It's steel on steel | NamTaf wrote: | 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 wrote: | > 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. | lowbloodsugar wrote: | The economist is playing Factorio now. | just_boost_it wrote: | 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 wrote: | 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. | smileysteve wrote: | 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. | NamTaf wrote: | 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. | zokier wrote: | https://en.wikipedia.org/wiki/European_Train_Control_System#. | .. | smileysteve wrote: | This wasn't a "why don't they just" response though because | the article does touch on GPS and the issues it poses. | | The Arduino comment was not supposed to be taken literally as | a production solution. | | There's a big difference between "why don't they just" and | "these problems spelled it in the article seem overstated" | olivermuty wrote: | To be fair, <<why don't they just>> has also made a lot of | startup founders very wealthy over the last 15 years ;) | NamTaf wrote: | 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. | jen729w wrote: | > 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/progr. | .. | smileysteve wrote: | But this is a "tech" problem where signals and switches | operating by humans are error prone, and the technology to | automate those exists. | | The article is about a tech solution and deployment never | able to come (in the U.S.) | smileysteve wrote: | Coincidentally, I have worked with localized location beacons | deployed to nationwide chains of stores that help you find | the aisle the item you're looking for is on. | smileysteve wrote: | > There's way more than "a few" dead spots, and what happens | if those repeaters fall over? | | Presumably, given the 2 sets of analog systems currently in | place, you fail safe to the inefficient systems in the | article, when a vehicle doesn't know it's location. | naijaboiler wrote: | IT engineers routinely do that to other fields as well. I'm a | doctor and tech guy. The amount of times I have to read the | ignorant arrogance of some guy thinking some ML is about to | replace doctors... I wish people will just stick to what they | know best, and approach other fields with respectful | curiosity. | smileysteve wrote: | I do have experience using location beacons where GPS isn't | available, along with inferring location from other sensors | though... | matthewmacleod wrote: | 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. | FredPret wrote: | >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. | | Since many current systems do not meet those criteria | (another comment mentions a "communication system" of writing | down the day's train drivers' cell numbers on a note), I'd | argue that any improvement towards an ideal system is a step | up. We can't wait for perfection. | NamTaf wrote: | Those steps up already exist. The railway I work for has | in-cab radios that we routinely measure the signal coverage | to confirm minimal black spots, plus there's also GSM | phones (as in, hardwired in the driver's cab), in all our | locos. | kposehn wrote: | To be fair, Brazil has been using GPS-based dispatching for | quite a while. While I haven't investigated their | implementation in-depth, almost the entirety of the long | distance rail network has switched to it and no longer uses | wayside signaling, preferring to track entirely via GPS. | smileysteve wrote: | I never thought a comment about an Arduino and a few sensors | would be taken so literally as a finalized product. | sitkack wrote: | 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 wrote: | 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 wrote: | 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. | kposehn wrote: | 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). | bobthepanda wrote: | This is already possible on small isolated networks (I | think there are a few heavy haul lines like this in | Australia.) | | The issue with _networks_ is that it is impossible to | roll out automation all at once, and the intermediate | mixed automated /non-automated network is more complex | and harder to do safely and reliably. | KaiserPro wrote: | > 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 wrote: | > 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 wrote: | > 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. | pestatije wrote: | 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 wrote: | 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. | pstuart wrote: | tl;dr -- fingerprint the magnetic properties of the rails | themselves and map accordingly. | | This is incredibly clever and I hope this catches on. | ChildOfChaos wrote: | Well i'd imagine when they touch, that's kinda bad for safety... | lb1lf wrote: | Just after two trains had crashed at Asta 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 Asta 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 wrote: | 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 wrote: | 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 wrote: | 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. | lb1lf wrote: | I only know what i've read about it in the papers, but I | think the concept was that the trains and track are | fitted with instrumentation enabling the train controller | to see in real time exactly what segment of track any | train is on at the moment; he will then periodically | authorize a train to occupy the X next segments. | Presumably the system is interlocked so that it is | impossible to authorize two trains to occupy the same | segment at the same time. | | If a train finds itself on a segment it has not been | authorized for, it stops - regardless of what the driver | thinks of the matter. | NamTaf wrote: | That system is track circuitry that uses relays to detect | rolling stock when they short the two rails via their | wheels. That exists widely, and it identifies that | rolling stock is present in a track section. That same | relay also locally (as in, on the ground at that | location) triggers any signals to switch to red. | | Controllers can't then give authorisation to another | train to enter that section, nor can they override any | red signal. In cases where it applies, they also can't | remotely control track switches to enter this occupied | section. However there's _nothing_ with that system that | then controls the rolling stock itself, so a driver can | still SPAD if they don't see or ignore the red, and the | remote network controller absolutely cannot stop a train | that is hurtling towards an occupied section. That's all | on the driver in the cab. | | Fun fact: track clips are used by track gangs to short | these sections in lieu of a big axle sitting on it, which | is one of the methods of providing site control to the | gangs so trains don't enter their worksite. It's | certainly not the only one, though. | lb1lf wrote: | I googled around a bit out of curiosity, and it appears | the remote control is indirect - the train controller can | override a green signal to red. (Presumably not the other | way around!) | | All trains have instrumentation which will cause them to | stop if they pass a red signal. | | The gritty details appear to be in the | Togframforingsforskriften, however this has been repealed | a couple of years ago, presumably to bring us in line | with EU regulations - but I am too tired to try to figure | this out tonight, though I have always been a sucker for | figuring out how signalling systems work... | zidel wrote: | For information specific to Norway (in Norwegian) there | is a lot here: | | https://trv.banenor.no/wiki/Forside | | https://www.jernbanekompetanse.no/wiki/Forside | NamTaf wrote: | Yup, any controller can set a signal to red (that's how | we do track blocks, said clips are the backup to that | because you always want the dude in the sky to know | you're there). | | Not all trains have kit to stop a SPAD, unless you meant | specifically in the instance of the operator involved in | this incident. Some do, but it's absolutely not universal | around the world. For example, Automatic Train Protection | (ATP) can do this, but it requires both a track-side | magnet and the rolling stock to have the kit for it. We | use that to trigger our driver vigilance system | acknowledgement when approaching suburban passenger | stations. Failure to acknowledge the vigilance prompt | will throw the brake to emergency and stop the train. | | That said, it's absolutely not present out in the Wild | West of freight (because maintaining that many ATP | magnets is insanely prohibitive). | Tsiklon wrote: | This is a bafflingly casual regard to safety, with not even a | token based system to grant access to a particular section of | track. The problem that caused this accident was solved in the | 1800's. | pmyteh wrote: | Well, the train didn't have the (notional) token, so the | signal was correctly at danger. Which is the 1800s solution | to the problem (absolute block signaling). And in the 19th | century it was _also_ difficult to reach train drivers who | passed signals at danger, due to a lack of radios etc., which | did cause accidents when signals failed or drivers passed | them at danger. | | Box-to-train emergency communication was itself definitely a | solved problem by the mid 20th century, though... ___________________________________________________________________ (page generated 2022-10-01 23:00 UTC)