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Why do railway tracks have crushed stones alongside them?
- Twixes 3y agoFascinating how such a simple solution is so timelessly effective. A "framework" going two centuries strong.
- bobthepanda 3y agoFor the majority of track, this is fine. High speed track uses ballastless track because at high speeds, making gravel fly is very damaging. (It also tends to be noisier and less smooth.) https://en.wikipedia.org/wiki/Ballastless_track https://en.wikipedia.org/wiki/Ballastless_track
- jen729w 3y agoAppreciate the link, could you edit the `.m` out of the URL so it doesn’t point us all to the mobile version? Ta. > Therefore, ballastless tracks must be concreted within a tolerance of 0.5 millimetres Wow.
- nayuki 3y agoIt would be even better if Wikipedia themselves fixed the problem. Here's how I would like to see it: There is only one URL per article, not a desktop URL versus m-dot URL. When you land on the page, if you have no cookie, then Wikipedia autodetects based on your size/orientation/device and gives you a desktop or mobile layout. If you choose to override the presentation, a cookie will be set, and all future visits will use your preferred layout. Personally, I'm on desktop all the time and I am peeved by people who post "m." links because the mobile version hides some useful features.
- fransje26 3y agoIn France they use ballasted track for their high speed trains. Even the newest tracks. With daily operational speeds up to 320 km/h, and with some tracks rated for speeds up to 350 km/h.
- giraffe_lady 3y agoIt's not impossible just has different tradeoffs. IIRC lower upfront cost but higher long-term maintenance. Also idk I just lived next to a tgv line for a few years but it's loud as a fucking jet even dug into the channels they use around residential areas.
- bobthepanda 3y agoNoise reduction techniques sometimes channel or reflect noise instead of absorbing it, so it is only quieter for some people in some areas and louder for others.
- bell-cot 3y agoThe Romans were using crushed stone in (non-rail-) road construction more then two millennia ago, and it was an old technology then: https://acoup.blog/2023/06/02/collections-roman-roads/ https://acoup.blog/2023/06/02/collections-roman-roads/
- quickthrower2 3y agoRails on rubies
- michaelsshaw 3y agoI was riding the train to work about a year ago and randomly googled this exact issue. I was amazed at how much thought actually goes into designing the ballast, as I had always assumed it was just some random fine gravel.
- SoftTalker 3y agoMaybe I missed it but is there a type of stone that is used, or just whatever is locally available? Around where I live that would be limestone but I am guessing that's too soft for this sort of use.
- Sharlin 3y agoAlmost everything always has much more thought given to it than it might first appear. Civil engineering is quite a fascinating subject, not least because how old it is, by far one of the earliest branches of engineering.
- rootusrootus 3y ago> Almost everything always has much more thought given to it than it might first appear. This statement ought to be in the guidelines for HN.
- Sharlin 3y agoOh, definitely.
- digestives 3y ago> Almost everything always has much more thought given to it than it might first appear. A credo to live by in work and in general - one of the most terrifying phrases in the English language is "it's just...".
- dark-star 3y agoModern high-speed tracks don't use ballast stones anymore though
- ant6n 3y agoDepends on the high speed rail system. Not all use slab track.
- guidedlight 3y agoThe low pressure air below passing trains travelling over 300km/h can cause "ballast lifting". i.e. Where ballast can be lifted up and become mobile causing safety issues, as well as accelerated deterioration of the track. High-speed trains therefore use concrete track beds.
- lostlogin 3y agoThat’s terrifying. Travelling across France I soon came to dislike going under bridges and tunnels and the compressive effect it had on air as you hit them. That it’s also capable of sucking up rocks came as news to me, but it isn’t really surprising.
- andbberger 3y ago> Travelling across France I soon came to dislike going under bridges and tunnels and the compressive effect it had on air as you hit them. modern high-speed trainsets are pressure sealed for precisely that reason
- rapnie 3y agoIn the Netherlands there is an ongoing debate on the use of ballast stones giving off quartz dust that can cause lung disease and cancer. https://www.dutchnews.nl/2021/04/prorail-is-jeopardising-workers-health-by-inaction-over-quartz-dust-zembla/ https://www.dutchnews.nl/2021/04/prorail-is-jeopardising-wor...
- bluescrn 3y ago[flagged]
- noduerme 3y agoIt's true, and it's odd, because the impulse clearly comes mostly from a desire to level economic inequalities - yet it comes from people who can afford to bike to work, or work from home. In that way it resembles a colonial attitude toward one's own society, at precisely the time when clean, carbon-neutral, fast and efficient personal transportation has come within reach for people below the social status of the proponents of ecological purity. The fact that they don't welcome its availability but instead reach for the next lever by which to reduce living standards and mobility (in the name of "justice") speaks to the classism and privilege underlying their crusade for purity.
- deleted 3y ago[deleted]
- nomilk 3y ago[flagged]
- ggambetta 3y agoHonest question, genuinely curious, I'm not picking on you; what's the point of pasting a ChatGPT response to a question? I've seen colleagues do this on internal mailing lists, even some of my friends do this on our group chats. I really don't get it. If I wanted the opinion of a language model, I'd ask a language model (and I do semi-frequently for certain questions). Getting ChatGPT output from an human rubs me the wrong way, like getting a LMGTFY link. But I assume both in your case and my friend's that the intent isn't to be passive aggressive. Help me understand?
- buildbot 3y agoI've seen this ~10 times today - They are all phrased the same way too. This person seems like an actual person and not a bot, so IDK. It's really, really annoying. If we wanted to, we could ask chatgpt ourselves.
- martyvis 3y agoClearly they all want to welcome their AI overlords.
- nomilk 3y agoReason for posting: I was surprised at how economical (in terms of words and, most importantly, reader time) GPT was compared to a human in answering the same question, without sacrificing accuracy. Thanks for pointing out that it's distracting; I hadn't considered that before posting.
- londons_explore 3y agoThis article doesn't explain one interesting bit: It is important that these crushed stones stay clean. If dirt gets in them, known as fouling, filling the gaps between the stones, then eventually it will cause a derailment. Briefly, the stones move slightly as each train passes above them. The tracks 'float' on the denser stone. This effect helps keep the track straight and level - higher regions get pushed down, while lower regions raise themselves up. Fouling stops this effect, and eventually the track will become so uneven that a derailment happens. To prevent this, a big part of railway maintenance involves digging out all the stones, washing them to get rid of sand and soil, and putting them back. Usually done every 25 years or so.
- dheera 3y agoStupid question from a software person: Why don't they just pour cement, epoxy, or tar over all the stones to fix them in place, fill in the gaps, and prevent dirt from getting in them?
- tedunangst 3y agoHow does the water drain through them?
- dheera 3y agoAgain here's my software mind: (a) If you fill all the gaps, water can't get in in the first place, and it doesn't need to drain. Abstract out the problem. (b) If water can still get in, it can also get out.
- grishka 3y agoExcept sometimes water falls out of the sky and it needs to drain somewhere.
- dermesser 3y agoThe rocks also need to be able to move a bit for elasticity, and have sharp edges. For that you also replace a part of the ballast every few years. That's hard to do when everything is sealed. Even with such "glue", the lifetime couldn't be eternal, after all.
- kingkongjaffa 3y agoIf you run a high speed train over a ballasted track the under carriage aerodynamics suck the ballast up and they can hit the bogeys and axles and cause cracks in the train axle. If this happens in a bad way it can derail the train. This abstract has a good summary https://research.birmingham.ac.uk/en/publications/a-full-scale-experimental-and-modelling-study-of-ballast-flight-u https://research.birmingham.ac.uk/en/publications/a-full-sca... So the question becomes can we replace ballast with some other mechanism where this doesn’t happen?
- luplex 3y agoWe can and do for many new high-speed rail developments: https://en.m.wikipedia.org/wiki/Ballastless_track https://en.m.wikipedia.org/wiki/Ballastless_track It's more expensive to build and fix, but it's also more reliable and needs less maintenance.
- seszett 3y agoI'm pretty sure TGV tracks do use ballast though, don't they? And they are among the fastest trains in operation, so it seems to work fine for them.
- kingkongjaffa 3y agoYeah the occurrence is fairly rare which is why we don’t do much about it. And we trust that NDT(non destructive testing) like die and ultrasonic etc, periodic testing will catch any cracks.
- willyt 3y agoHere’s a TGV speed test on a ballasted track. There’s an axle cam and it doesn’t look like there’s big chunks flying about but it does stir up a lot of dust at 575km/h (~360mph) https://m.youtube.com/watch?v=EOdATLzRGHc&t=11s&pp=ygURdGd2IHNwZWVkIHJlY29yZCA%3D https://m.youtube.com/watch?v=EOdATLzRGHc&t=11s&pp=ygURdGd2I...
- x3874 3y ago...so many words and just at the end they comment on 'flooding' - whereas everyone knows that a top function of ballast is to prevent water buildup / facilitate drainage.
- h2odragon 3y agoWaverly, TN had bad floods a couple years ago because their long span of train tracks around the bottom of the hill hadn't had its drainage maintained. The ballasted, built up tracks trapped a large volume of water which blew out finally and caused catastrophic flooding. The sheriff said he'd been complaining to the railroad for 2 years about the water building up, trying to get them to clean out the drains. That's an incredibly busy line tho. After the floods they had the train tracks back up and running in weeks, before some the roads through town. I'm told they built exactly the same plan that had been there before, inadequate drainage and all.
- x3874 3y ago"drainage" as in primarly preventing fouling of ties, not as in "preventing water buildup behind a trackbed". I would call that obvious, but maybe i have too diverse interests as to nit know this... For permitting regular water flow tru a trackbed: what culverts etc. are for.
- h2odragon 3y agoCulverts, aqueducts, etc, yes. It all has to be maintained. Even when it's designed well (and the current design is minimal); all those measures have to be kept clear of obstructions. In this case they were not, and very likely still are not.
- aurizon 3y agoAs time goes by the ballast settles and under repeated heavy loads and the underlying land becomes a little uneven. In comes the Tamper, a ballast tamping machine. This is a long heavy machine that runs on the track.Quite strong it lifts a length of track under load a few inches and tamping arms reach down and force fresh ballast under with dynamic level sensors and moves on down the track. Tracks are surveyed with sensors on trains and ballast tamping/washing/etc are scheduled. https://www.youtube.com/watch?v=WqLynLWLd8Y https://www.youtube.com/watch?v=WqLynLWLd8Y
- deleted 3y ago[deleted]
- rhn_mk1 3y ago> Without the ballast in place, railway lines would simply not be able to cope with the stress from the weight of the trains passing over them, not to mention the impacts of expansion and contraction. How does this relate to tram lines? They don't seem to have much ballast at all, and they are often just inset into asphalt, so there's no draining, and the asphalt presumably limits expansion and contraction?
- mkl 3y agoTrams are much lighter and have way fewer carriages/cars, so I expect the need is much reduced. The foundation of the road is probably even more sturdy than the ballast, and there are gaps between rail sections for expansion.
- usr1106 3y agoThe speeds you can reach on traditional tracks embedded into streets is much lower. Outside of cities where trams run at higher speed ballast is preferred. Modern tram tracks have a steel-enforced concrete base under the street, similar to ballast-free highspeed tracks.
- snowwrestler 3y agoLong-haul rail lines are engineered to support freight loads, which can be extreme. Local passenger lines have lighter cars that are mostly enclosed air, and commensurately lighter engines as well.
- usr1106 3y agoIt's an exaggeration to claim that ballast would have been used for railway tracks for centuries as the article claims. Railways haven't even existed for 2 centuries. Although there are only 2 years left. Still in the 1970s, only 50 years ago, Finland had railways build with weaker material, small round stones.
- zimpenfish 3y ago> It's an exaggeration to claim that ballast would have been used for railway tracks for centuries "At Whitley in 1704, when the word first occurs in a railway context, clinker from the salt-pans was used 'for the ballast of the waggonway'"[1] By my reckoning, 2023 - 1704 = 319 which I think comfortably fits into "centuries"? [1] https://www.railscot.co.uk/articles/A_brief_history_of_railway_track_ballast_with_special_reference_to_the_north_east_of_Scotland/ https://www.railscot.co.uk/articles/A_brief_history_of_railw...
- usr1106 3y agoOf course it always depends what borders you draw. I started with steam railways. Of course horse driven railways existed before, but they were of a completely different load class. I don't know what clinker from salt mines looks like. But I guess it's significantly different from sharp, crushed rocks the NZ article describes. Also the Scottish article says that just some sentences later that ballast had completely different properties those days. Some ballast has been used for centuries. But not the kind consisting of sharp, crushed relatively coarse rock pieces we know today.
- zimpenfish 3y ago> Of course it always depends what borders you draw. You seem to be rapidly redrawing yours in a different place all of a sudden. "It's an exaggeration to claim that ballast would have been used for railway tracks for centuries" You may well have meant "ballast (specifically sharp crushed rocks as they use nowadays)" but that's a very different statement. > Some [X] has been used for centuries. But not the kind [...] we know today. I mean, yeah, truism.
- softgrow 3y agoThere is a longer article https://www.ejrcf.or.jp/jrtr/jrtr15/pdf/f38_tec.pdf https://www.ejrcf.or.jp/jrtr/jrtr15/pdf/f38_tec.pdf from a series on Railway Technology from the Japan Rail and Technology Review https://www.ejrcf.or.jp/jrtr/technology/index_technology.html https://www.ejrcf.or.jp/jrtr/technology/index_technology.htm... . It contrasts ballasted track with slab track and purports a 9 year breakeven on the higher construction cost but reduced maintenance cost. It notes that the main Shinkansen from Tokyo to Osaka is ballasted track and I understand it still is. Mind you how you could ever changeover on this super busy line is going to be somewhat difficult.
- ofalkaed 3y agoThis gets its purpose regarding plants a bit wrong, the only time roots would be any issue is on tracks which have not been used in quite awhile and at that point the tracks will almost certainly have other issues which need to be addressed before they get used again. The metal on metal of the wheels on tracks often causes sparks and these do occasionally cause fires in dried vegetation alongside/on the tracks which the ballast helps to keep in control, which is why the ballast generally extends further from the edges of the tracks than is needed for stability reasons. If you work track maintenance part of your job will be torching any plants growing too close to the tracks especially on grades where wheels often slip and brakes applied which can produce a surprising amount of sparks. They also have cars which spray weed killers alongside the tracks which run the line once or twice a year depending on conditions.
- bsaul 3y agoWith time i've come to realize any piece of engineering can be a source of inspiration, even to a software dev / architect like me. I feel like it took me a lot of time to figure this out, as i've got 20 years of experience. Anyone else ?
- jhallenworld 3y agoI watched a video just yesterday about wood ties vs. concrete ties. One of the arguments in favor of wooden ties in the US is that they are less brittle and thus more able to handle the frequent derailments we get. The nightmare scenario with concrete ties is that a loose wheel goes unnoticed for miles and cracks every single tie. They mentioned a previous test experience with older concrete ties held together with naked angle-irons. A derailment severed all of the irons. https://www.youtube.com/watch?v=UtyTTijswwg https://www.youtube.com/watch?v=UtyTTijswwg
- mberning 3y agoThere are a lot of parallels with modern hardscape construction. Nowadays many builders grade the soil base, add a woven stabilization fabric, then add clean angular stone, and finish with a finer angular stone on top. I wonder if railroads are using any geotextile fabric under their stone these days.
- ajot 3y agoThey do, or at least I've seen it in some railway renovations here in Argentina (through posts in SkyscraperCity forum). The funny thing is, when the state runs out of money, they start to cut corners and the geotextile fabric is one of the first things to go.
- mberning 3y agoThat’s sad and hilarious. Geotextile fabric is so cheap and adds so much longevity to these type of projects.
- swayvil 3y agoIt's purely aesthetic. The sharp edged stone contrasts nicely with the polished rail and the dark woody tie.
- Octopuz 3y agoDuring a boy scouts summer camp, we were on a separated camping area near a railroad track. We created a fireplace and used some stones from the track to build the fire on. A pretty big mistake as it turned out. Because the stones were in fact vulcanic, they exploded when heated - so we were bombarded with stone fragments.
- cratermoon 3y agoA nice video with good visualizations of the mechanics of the ballest from ABC Science: https://www.youtube.com/watch?v=TlSOMfDX-yY https://www.youtube.com/watch?v=TlSOMfDX-yY
- euroderf 3y agoSeveral comments mention track buckling in extreme heat. When this happens, how is it resolved ? Does the track usually revert to its original positioning at all points, or does every stretch of recently-buckled track have to be inspected and possibly realigned ?
- jcrawfordor 3y agoIt depends on the severity of the problem. The track may satisfactorily straighten itself out as it cools. It might mostly straighten itself out, but there could be lasting geometry problems from it settling differently than it was before. This will need to be corrected by a tamper, which basically vibrates the ballast under the tracks so it "flows" as the track is pulled into the correct position. In especially severe cases, the track may need to be inspected and have some hardware replaced---things like joint bars and track fasteners. Tampers have a reference system based on axles far apart whose relative positions are measured by a simple optical setup. So especially with modern computer controls, the operator can program the correct track profile into the tamper and then it slowly advances along the track pulling it back into position. Since tampers are slow and there are only so many around, a lot of railroads have work trains or even hirail trucks with optical equipment to measure the track geometry so that they can inspect for tolerances more frequently. The exact tolerances depend mostly on running speed... a train moving very slowly can often handle even badly out-of-alignment track as long as it is well attached to the ties (so the distance between the rails stays correct). So you will often see industrial sidings in really bad shape since they're only used occasionally at 15mph. But once trains get up to 50mph and faster they become a lot more sensitive to the geometry and you start worrying about damage and derailments if things are out of whack. So the mainline track gets inspected a lot more frequently, often a simple visual inspection by MOW workers in a hirail is done daily besides of course train crews reporting areas with a rough ride.
- BenjiWiebe 3y agoSpeaking of it being more of an issue at high speeds, the freight trains through our area go through far more slowly when we are having a hot spell. I've been told it's to be more safe on the expanding possibly-not-perfectly-straight rails.
- irrational 3y agoMy first thought, on reading the title, is maybe the sparks sometimes thrown off by the trains would catch dry weeds on fire if they were near the tracks, so the crushed stones give the sparks somewhere safe to land.
- chrisstanchak 3y agotl;dr Crushed stones, or ballast, along railway tracks provide stability, aid drainage, control vegetation, and distribute train load.
- mintaka5 3y agodrainage so the rails don't float off somewhere else due to erosion. not alongside them either. under them.
- fzeindl 3y agoI am working for a railroad company at the moment, we learned cool stuff during onboarding. Modern train have an electromagnetic emergency brake system that uses a large magnet lowered onto the rail to stop. Also the standard braking system using fluids has a clever indirection where it does not activate the brake when pressure rises but when it drops. This is because when a waggon gets loose and the braking line rips and fluids get's out, the waggon should immediately brake as soon as pressure drops.
- askvictor 3y agoI'm curious why all brakes aren't designed like this.
- ericjang 3y agoI entered the title question of the article into ChatGPT, as I was curious whether it could factually synthesize information on the Internet similar to how this article did. Notably, it missed the detail about keeping vegetation away <chatgpt> Railway tracks have crushed stones, commonly known as ballast, alongside them for several important reasons. Here are the main reasons for using ballast on railway tracks: Stability and Load Distribution: Ballast provides stability to the railway tracks and distributes the load of the trains evenly. The crushed stones interlock with each other and form a stable base for the tracks. This helps prevent the tracks from shifting or sinking under the weight of the trains. Drainage: Ballast allows for effective drainage of water from the tracks. The open spaces between the crushed stones allow water to flow away from the tracks, preventing the accumulation of water. Proper drainage is essential to maintain the stability of the tracks and prevent damage caused by water-related issues like erosion or track bed saturation. Track Alignment and Adjustment: Ballast allows for easy alignment and adjustment of the tracks. The crushed stones can be added or removed as needed to maintain the proper track alignment and ensure a smooth ride for trains. This flexibility is especially important during track maintenance or when new tracks are being laid. Noise and Vibration Damping: Ballast helps in reducing noise and vibrations generated by passing trains. The layer of crushed stones absorbs and dampens the vibrations, minimizing the impact on the surrounding environment and nearby structures. Track Maintenance: Ballast provides a protective layer for the tracks. It acts as a barrier between the track infrastructure and the underlying soil, preventing soil movement or erosion that could damage the tracks. Additionally, ballast makes it easier to detect and repair any issues with the track, such as loose fastenings or track bed settlement. Overall, the use of ballast alongside railway tracks is crucial for maintaining the stability, alignment, drainage, and longevity of the tracks, ensuring safe and efficient train operations. </chatgpt>
- andix 3y agoAren’t roads built in a similar way, just with a different surface?
- chromanoid 3y agoRelevant machine that is called Gleisschotterbettungsreinigungsmaschine in German. Nice video for children about it (in German, there's probably an inofficial YT video where you can switch on automatic subtitles): https://kinder.wdr.de/tv/die-sendung-mit-der-maus/av/video-sachgeschichte-gleisschotterwaschanlage-100.html https://kinder.wdr.de/tv/die-sendung-mit-der-maus/av/video-s...
- fransje26 3y ago> Gleisschotterbettungsreinigungsmaschine 39 letters..
- bigbluesax 3y agoIt looks funky, but it's just railway track gravel cleaning machine, without the spaces.
- guy98238710 3y agoThe stones must be good reflectors of noise, which makes the ballast rather undesirable under trams in cities. I wonder why is it still used in such circumstances instead of having noise-absorbing soil and grass under and around the tracks as is sometimes done.
- iggldiggl 3y agoBallasted track is cheaper to build, so somebody needs to be willing to fund the difference in costs. This especially applies to existing infrastructure, where it's more likely than an upgrade to green track might have to be funded by the municipality alone.
- wg0 3y agoDoes anyone know about that device on electric engines that touches the wires above? Why is that it doesn't spark and do the overhead cables need frequent replacement because of being constantly rubbed against?
- mission_failed 3y agoIt's called a pantograph. There is a carbon strip on the top of the pantograph that is typically replaced every couple of months as it wears. The overhead wire isn't wire like you normally see, it's more like a thick copper bar that is unwound and has a flat surface on the bottom that the carbon strip runs on. The overhead does wear out over time, but is much longer lived than the carbon strips. Sparking I think is when there might be damage to the overhead wire that temporarily interferes with current as the strip passes over, as you see sparks happening at the same place as trains pass
- haspok 3y agoAlso noteworthy, the overhead wires usually zig-zag from left to right, so they touch different parts of the pantograph surface as the train moves.
- fransje26 3y agoOh, but it sparks... https://youtu.be/p5u_5iQ3Ego?t=342 https://youtu.be/p5u_5iQ3Ego?t=342 (By the way, the part where it goes over a turnout at 500 km/h as if it is nothing is also pretty amazing.. https://youtu.be/p5u_5iQ3Ego?t=291 https://youtu.be/p5u_5iQ3Ego?t=291)