10 ms·

This is slightly depressing as I've been looking forward to Isaac Asimov's "belts" for some time now. A giant loop of of parallel walkways of graded speeds, con

This is slightly depressing as I've been looking forward to Isaac Asimov's "belts" for some time now. A giant loop of of parallel walkways of graded speeds, continuously operating for city-wide underground transport. I guess now that they'd have the escalator maintenence issues with steroids.

nine_k 8y ago
While at it: trains are so much more convenient. Walls and roof protect you from excessive heat, excessive cold, wind, rain, snow, and the sound the mechanisms make. Seats allow you (or people more tired than you) to sit and work, read, or rest, especially when you ride for an hour. Also, train infrastructure is vastly narrower than such a collection of moving bands, and is readily available for maintenance when no trains are going. The downside is that trains have to have stations. But the moving band will have to have a "station" all along it.
- TylerE 8y ago
  It's not quite as clear cut as you make it sound, imo. A belt system would run continuously, which means no waiting for the next train, and you don't have to slow down at every intermediate stop, which should improve average speeds.
  - nine_k 8y ago
    At the cost of much decreased capacity, because a lot of the system moves pretty slowly; you cannot make the bands narrower than what it takes to stand with two feet, and likely wider for some safety. Also, the amount of area and mass to move per passenger grows quite a lot, because most passengers will want to be on the fastest band, and all the gradual bands will be much less occupied. The system can work reasonably when the moving bands are very lightweight, thin layers moved by a motor without many (or any) moving parts (the way maglev moves). It also should have absurdly low friction: unlike a train, it has a lot of contact surface. To say nothing about turns. Not that it's impossible, but technology-wise we're totally not there yet to make such a thing practical.
    - kqr 8y ago
      So have one fast band between "stops", and then large concentric circles of gradually slower bands surrounding each "stop"?
- mikeash 8y ago
  No need for stations next to the moving band. The outer bands move slowly enough that you can step on and off at any point. The center bands could have seats, and you could wall the whole thing in to protect from the weather.
  - akira2501 8y ago
    > The outer bands move slowly enough that you can step on and off at any point. Add that to the "Places I don't want to be during a system failure."
    - mikeash 8y ago
      Yes, it would probably be best to stay several hundred miles away from the whole thing.
  - freddie_mercury 8y ago
    Moving slowly enough for whom to step off? The 90 year old lady with a walker? The toddler? Stephen Hawking in his wheelchair? How slow is it going to accommodate every single person's movement capacity? How small is the gradient between each belt to allow them to move between belts? How wide does this whole thing end up needing to be?
    - TeMPOraL 8y ago
      > Moving slowly enough for whom to step off? The 90 year old lady with a walker? The toddler? Stephen Hawking in his wheelchair? Why not? Don't they use moving floors on airports already? (Also, do toddlers walk alone on the busy streets?) Here's a design I just sketched in Factorio for a belt system with 3 speed levels, and an entry/exit for moving onto the belt system, and then between speed levels. https://imgur.com/c51pTnP https://imgur.com/c51pTnP (For those who don't know Factorio - the blue belts are the fastest, the yellow ones are the slowest.)
      - ubernostrum 8y ago
- thaumasiotes 8y ago
  Being underground also protects you from excessive heat, excessive cold, wind, rain, and snow. Being underground won't protect you from the noise of the mechanisms, but neither do the walls and roof of a train. Being on a train is loud. Large crowds will cause heat within the system that will likely need to be managed, but -- like the noise -- this is equally true of trains. How are any of those things an advantage of trains over a system of underground walkways?
  - mwilliaams 8y ago
    Trains aren't (all) loud. I just rode an Amtrak yesterday. It was surprisingly quiet.
    - Symbiote 8y ago
      Tight curves tend to be loud, as is old track, or track that isn't welded into very long lengths. Locomotives are quieter than having motors on each carriage. In much of Europe that makes trains quiet, except metro trains with tight curve. People excluded, I think non -metro trains are usually quieter than cars. I've only used one train in the US, which ran on jointed (not welded) track so made the 'clickety clack' noise, but presumably that varies and the North East is better.
  - nine_k 8y ago
    I just happen to ride a lot of above-ground trains. E.g. much of the New York City subway goes above ground, sometimes pretty high, in Brooklyn and Queens. Same applies to quite a few cities (e.g. London and Moscow, off the top of my head). But okay, let's imagine out underground walkway. Since it's underground, you can't walk on and off where you want; you only walk off where there's way up to the ground. This eliminates much of the allure of the system. Now you want to plan ahead and be ready to get off when you're next to the exit. If you missed your exit, you have to move to the next exit, or maybe cross the tunnel and go to the band of the opposite direction, and walk back a bit. Please notice how the low-speed bands then need to run the whole length of the tunnel, adding little to the carrying capacity: few people want to travel at the speed of walking when traveling at the speed of a train is a few meters across. If we let only the faster band(s) through the length of the tunnel, and limit the slower bands to the exit areas (pretty long and wide), we'll face the problem of walls: our band is moving fast, and nothing separates it from the walls. So we sort of need inner walls on the band. But they need doors to allow people in and out in the exit areas. And the doors need to be shut when the band is in the tunnel. It starts to look like a... train? Only an endless train with a peculiar way of boarding. This endless train also has a downside: if anything goes wrong, the whole band/train has to stop, it cannot be re-routed. What if we segment the band into individually routable parts? Only then they'll have to stop at exit areas to allow safe getting on / off them. Well, we have reinvented the subway.
- jfoutz 8y ago
  I liked the belt idea until i read about bubble cars. have a zillion cars with room for 3 people that are constantly circulating around a track, with roll on roll offs all over the place. hit a button, next empty car rolls off and stops for you. hit a button inside for your destination, accelerate back to the main track speed and you're on your way. it's kind of like a people mover, but has the ability to actually stop, thanks to the split/merge at the stops.
  - Jagat 8y ago
    If there's just one track, will other zillion-1 cars behind my car stop, while it loads me?
    - jfoutz 8y ago
      no, stops would have real roll on roll offs - you see them in actual train yards, it's hard to find a good picture. here's the general idea from a video game https://i.imgur.com/7gNHkNP.jpg https://i.imgur.com/7gNHkNP.jpg ideally multiple cars could pull out of the main track for loading and unloading(in which case you might have to wait a bit for the car in front).
    - femto 8y ago
      Why not integrate a "bubble car" into building lift/elevator systems? The capsule brings you 20 km from home, switches to the rails within the lift well and zips up, depositing you directly on your floor. Thirty years ago lots of people were talking about mass transit systems with small individual capsules. According to one of my engineering lecturers at the time, a limitation was that there simply isn't enough room on the ground to have all those capsules loading and unloading people in a CBD with lots of skyscrapers.
      - jfoutz 8y ago
        I think the point about how much space is needed for high density loading and unloading is excellent. if you're willing to slow down the main line in specific areas, you can use a lot more of the siding rail for loading. I have no doubt your lecturer is far more informed than i will ever be. I will assert that it's not really 1990 any more, and far more employers would be willing for employees to show up and leave at different times. Car congestion alone has made a lot of employers willing to have start time anywhere from 7 to 10. Which might alleviate some of that burden. I also think, being able to take the whole trip without stopping - even if you occasionally have to go slower in high congestion areas - is much faster overall for each passenger. Which, in my humble opinion is a huge feature. If the cars are reversible, you can also have Y junctions and stack up loads of cars perpendicular to the main rail, and fill those cars like a normal train.
__s 8y ago
See also Robert Heinlein's short story The Roads Must Roll
- trukterious 8y ago
  Thanks! I found an audio version/adaptation, will listen later: https://www.youtube.com/watch?v=XAlagNId3fw https://www.youtube.com/watch?v=XAlagNId3fw
mattkevan 8y ago
They sound like an accessibility nightmare. Imagine an old person or someone with movement issues not quite making the transition between the slower and high-speed bands. They’d end up as sort of human bowling ball, knocking down other passengers like skittles. Similar thing happened to me on a crowded escalator at London Bridge tube station. Was about half way up when an old guy in front toppled back onto me. Thankfully I’d noticed he looked unsteady and managed to catch him under his armpits, otherwise we’d all have ended up in a heap at the bottom. I didn’t have the leverage to get him upright, so we stayed with me holding him until we reached the top. His shoes hit the metal plate at the end and I flipped him to his feet. We then gave each other a nod and went about our business.
- baud147258 8y ago
  In the subway tunnels beneath Montparnasse train station in Paris, there's a long stretch of corridor leading from the above-ground train station to the subway. Three moving sidewalk were installed, with one being higher speed, but they were forced to replace it with a normal-speed one, because of complaints and reliability issues. Source: https://en.wikipedia.org/wiki/Moving_walkway#Trottoir_roulant_rapide_(TRR) https://en.wikipedia.org/wiki/Moving_walkway#Trottoir_roulan...
  - adam-a 8y ago
    Very interesting. I found a video of an express walkway at a Toronto airport which is apparently still in use. It looks quite complex with foot plates which extend as the belt moves faster. I wonder what it's like to use. https://www.youtube.com/watch?v=GvfF4TeXz7U https://www.youtube.com/watch?v=GvfF4TeXz7U
    - maz- 8y ago
      Used it last year. It's fun! You have to stand in the right spot though otherwise the plates extend under your feet which while I don't think it's dangerous, does feel a bit sketchy.
- Tharkun 8y ago
Nanite 8y ago
I once had the pleasure to use a high speed travelator in Paris going at 8mph, I recall they used several acceleration stages in series before getting on the main section. Also reminded me of the ones portrayed in Asimov's novels. Too bad they shut them down almost a decade ago. https://www.thetransportpolitic.com/2009/05/21/paris-experimental-high-speed-moving-walkway-is-abandoned/ https://www.thetransportpolitic.com/2009/05/21/paris-experim...
deleted 8y ago
[deleted]
michaelbuckbee 8y ago
They've been roundly made fun of here on HN (and elsewhere) but the current electric scooter + smartphone app deployment that is taking place is about 80% of that vision.

nine_k 8y ago

While at it: trains are so much more convenient. Walls and roof protect you from excessive heat, excessive cold, wind, rain, snow, and the sound the mechanisms make. Seats allow you (or people more tired than you) to sit and work, read, or rest, especially when you ride for an hour. Also, train infrastructure is vastly narrower than such a collection of moving bands, and is readily available for maintenance when no trains are going. The downside is that trains have to have stations. But the moving band will have to have a "station" all along it.

TylerE 8y ago
It's not quite as clear cut as you make it sound, imo. A belt system would run continuously, which means no waiting for the next train, and you don't have to slow down at every intermediate stop, which should improve average speeds.
- nine_k 8y ago
  At the cost of much decreased capacity, because a lot of the system moves pretty slowly; you cannot make the bands narrower than what it takes to stand with two feet, and likely wider for some safety. Also, the amount of area and mass to move per passenger grows quite a lot, because most passengers will want to be on the fastest band, and all the gradual bands will be much less occupied. The system can work reasonably when the moving bands are very lightweight, thin layers moved by a motor without many (or any) moving parts (the way maglev moves). It also should have absurdly low friction: unlike a train, it has a lot of contact surface. To say nothing about turns. Not that it's impossible, but technology-wise we're totally not there yet to make such a thing practical.
  - kqr 8y ago
    So have one fast band between "stops", and then large concentric circles of gradually slower bands surrounding each "stop"?
mikeash 8y ago
No need for stations next to the moving band. The outer bands move slowly enough that you can step on and off at any point. The center bands could have seats, and you could wall the whole thing in to protect from the weather.
- akira2501 8y ago
  > The outer bands move slowly enough that you can step on and off at any point. Add that to the "Places I don't want to be during a system failure."
  - mikeash 8y ago
    Yes, it would probably be best to stay several hundred miles away from the whole thing.
- freddie_mercury 8y ago
  Moving slowly enough for whom to step off? The 90 year old lady with a walker? The toddler? Stephen Hawking in his wheelchair? How slow is it going to accommodate every single person's movement capacity? How small is the gradient between each belt to allow them to move between belts? How wide does this whole thing end up needing to be?
  - TeMPOraL 8y ago
    > Moving slowly enough for whom to step off? The 90 year old lady with a walker? The toddler? Stephen Hawking in his wheelchair? Why not? Don't they use moving floors on airports already? (Also, do toddlers walk alone on the busy streets?) Here's a design I just sketched in Factorio for a belt system with 3 speed levels, and an entry/exit for moving onto the belt system, and then between speed levels. https://imgur.com/c51pTnP https://imgur.com/c51pTnP (For those who don't know Factorio - the blue belts are the fastest, the yellow ones are the slowest.)
    - ubernostrum 8y ago
thaumasiotes 8y ago
Being underground also protects you from excessive heat, excessive cold, wind, rain, and snow. Being underground won't protect you from the noise of the mechanisms, but neither do the walls and roof of a train. Being on a train is loud. Large crowds will cause heat within the system that will likely need to be managed, but -- like the noise -- this is equally true of trains. How are any of those things an advantage of trains over a system of underground walkways?
- mwilliaams 8y ago
  Trains aren't (all) loud. I just rode an Amtrak yesterday. It was surprisingly quiet.
  - Symbiote 8y ago
    Tight curves tend to be loud, as is old track, or track that isn't welded into very long lengths. Locomotives are quieter than having motors on each carriage. In much of Europe that makes trains quiet, except metro trains with tight curve. People excluded, I think non -metro trains are usually quieter than cars. I've only used one train in the US, which ran on jointed (not welded) track so made the 'clickety clack' noise, but presumably that varies and the North East is better.
- nine_k 8y ago
  I just happen to ride a lot of above-ground trains. E.g. much of the New York City subway goes above ground, sometimes pretty high, in Brooklyn and Queens. Same applies to quite a few cities (e.g. London and Moscow, off the top of my head). But okay, let's imagine out underground walkway. Since it's underground, you can't walk on and off where you want; you only walk off where there's way up to the ground. This eliminates much of the allure of the system. Now you want to plan ahead and be ready to get off when you're next to the exit. If you missed your exit, you have to move to the next exit, or maybe cross the tunnel and go to the band of the opposite direction, and walk back a bit. Please notice how the low-speed bands then need to run the whole length of the tunnel, adding little to the carrying capacity: few people want to travel at the speed of walking when traveling at the speed of a train is a few meters across. If we let only the faster band(s) through the length of the tunnel, and limit the slower bands to the exit areas (pretty long and wide), we'll face the problem of walls: our band is moving fast, and nothing separates it from the walls. So we sort of need inner walls on the band. But they need doors to allow people in and out in the exit areas. And the doors need to be shut when the band is in the tunnel. It starts to look like a... train? Only an endless train with a peculiar way of boarding. This endless train also has a downside: if anything goes wrong, the whole band/train has to stop, it cannot be re-routed. What if we segment the band into individually routable parts? Only then they'll have to stop at exit areas to allow safe getting on / off them. Well, we have reinvented the subway.
jfoutz 8y ago
I liked the belt idea until i read about bubble cars. have a zillion cars with room for 3 people that are constantly circulating around a track, with roll on roll offs all over the place. hit a button, next empty car rolls off and stops for you. hit a button inside for your destination, accelerate back to the main track speed and you're on your way. it's kind of like a people mover, but has the ability to actually stop, thanks to the split/merge at the stops.
- Jagat 8y ago
  If there's just one track, will other zillion-1 cars behind my car stop, while it loads me?
  - jfoutz 8y ago
    no, stops would have real roll on roll offs - you see them in actual train yards, it's hard to find a good picture. here's the general idea from a video game https://i.imgur.com/7gNHkNP.jpg https://i.imgur.com/7gNHkNP.jpg ideally multiple cars could pull out of the main track for loading and unloading(in which case you might have to wait a bit for the car in front).
  - femto 8y ago
    Why not integrate a "bubble car" into building lift/elevator systems? The capsule brings you 20 km from home, switches to the rails within the lift well and zips up, depositing you directly on your floor. Thirty years ago lots of people were talking about mass transit systems with small individual capsules. According to one of my engineering lecturers at the time, a limitation was that there simply isn't enough room on the ground to have all those capsules loading and unloading people in a CBD with lots of skyscrapers.
    - jfoutz 8y ago
      I think the point about how much space is needed for high density loading and unloading is excellent. if you're willing to slow down the main line in specific areas, you can use a lot more of the siding rail for loading. I have no doubt your lecturer is far more informed than i will ever be. I will assert that it's not really 1990 any more, and far more employers would be willing for employees to show up and leave at different times. Car congestion alone has made a lot of employers willing to have start time anywhere from 7 to 10. Which might alleviate some of that burden. I also think, being able to take the whole trip without stopping - even if you occasionally have to go slower in high congestion areas - is much faster overall for each passenger. Which, in my humble opinion is a huge feature. If the cars are reversible, you can also have Y junctions and stack up loads of cars perpendicular to the main rail, and fill those cars like a normal train.

__s 8y ago

See also Robert Heinlein's short story The Roads Must Roll

trukterious 8y ago
Thanks! I found an audio version/adaptation, will listen later: https://www.youtube.com/watch?v=XAlagNId3fw https://www.youtube.com/watch?v=XAlagNId3fw

mattkevan 8y ago

They sound like an accessibility nightmare. Imagine an old person or someone with movement issues not quite making the transition between the slower and high-speed bands. They’d end up as sort of human bowling ball, knocking down other passengers like skittles. Similar thing happened to me on a crowded escalator at London Bridge tube station. Was about half way up when an old guy in front toppled back onto me. Thankfully I’d noticed he looked unsteady and managed to catch him under his armpits, otherwise we’d all have ended up in a heap at the bottom. I didn’t have the leverage to get him upright, so we stayed with me holding him until we reached the top. His shoes hit the metal plate at the end and I flipped him to his feet. We then gave each other a nod and went about our business.

baud147258 8y ago
In the subway tunnels beneath Montparnasse train station in Paris, there's a long stretch of corridor leading from the above-ground train station to the subway. Three moving sidewalk were installed, with one being higher speed, but they were forced to replace it with a normal-speed one, because of complaints and reliability issues. Source: https://en.wikipedia.org/wiki/Moving_walkway#Trottoir_roulant_rapide_(TRR) https://en.wikipedia.org/wiki/Moving_walkway#Trottoir_roulan...
- adam-a 8y ago
  Very interesting. I found a video of an express walkway at a Toronto airport which is apparently still in use. It looks quite complex with foot plates which extend as the belt moves faster. I wonder what it's like to use. https://www.youtube.com/watch?v=GvfF4TeXz7U https://www.youtube.com/watch?v=GvfF4TeXz7U
  - maz- 8y ago
    Used it last year. It's fun! You have to stand in the right spot though otherwise the plates extend under your feet which while I don't think it's dangerous, does feel a bit sketchy.
Tharkun 8y ago

Nanite 8y ago

I once had the pleasure to use a high speed travelator in Paris going at 8mph, I recall they used several acceleration stages in series before getting on the main section. Also reminded me of the ones portrayed in Asimov's novels. Too bad they shut them down almost a decade ago. https://www.thetransportpolitic.com/2009/05/21/paris-experimental-high-speed-moving-walkway-is-abandoned/ https://www.thetransportpolitic.com/2009/05/21/paris-experim...

deleted 8y ago

[deleted]

michaelbuckbee 8y ago

They've been roundly made fun of here on HN (and elsewhere) but the current electric scooter + smartphone app deployment that is taking place is about 80% of that vision.