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Public transport will always be able to pack more people into the same space. There is a minimum amount of space occupied by the vehicle's own matter. The rati

Public transport will always be able to pack more people into the same space. There is a minimum amount of space occupied by the vehicle's own matter. The ratio of that material to the occupant is a scaling law: the larger the vehicle, the higher the volume-to-surface, the denser the passenger-to-vehicle ratio can be. A standard R160 subway car carries up to about 250 people in an area that would be about the same as 5 Corollas positioned nose to tail, a starting ratio of about 10:1. If cars are made twice as dense, it's still 5:1. This is ordinary batching. The only thing that can carry more people more densely than a bus or train is the footpath.

davnicwil 8y ago
Yes you're absolutely correct - I guess my main question is could the space savings, like the pollution savings, be 'good enough' for it not to matter in practice, assuming that driverless cars become the 80% usecase for road traffic and today's 'massive 5 seater car for an average of 2 people' model goes away. It's also important to point out that of course, buses and trains shouldn't go away - they could indeed also have a bunch of problems solved by being self driving too, most notably the 24/7 running thing - they'd just be another option in the mix.
rhacker 8y ago
> Public transport will always be able to pack more people into the same space. While that's true, that's also just an argument for something we already understand. Are there possible arguments to be made about the number of busses and routes because it's not taking people point to point. What about the lul-time of day, where on-demand model is more efficient than driving empty busses around. They reduce schedules obviously. But now you're punishing passengers that start a shift at noon. There are more things to solve than just "the least amount of pollution and space." Totally unrelated but similar argument. The FAA introduced a new system and process for creating standard flight paths a few years ago. Flights around the nation started doing new things. TONS of people are now inundated by jet noise. They're now discussing just going back in certain areas to the old routes. They ONLY optimized for efficiency of route and didn't consider anything else.
- jacques_chester 8y ago
  > There are more things to solve than just "the least amount of pollution and space." The argument I was responding to was that self-driving cars would be sufficiently more efficient users of space that it would obviate the need for public transport. This was demonstrably false. > But now you're punishing passengers that start a shift at noon. Sure, but (a) that's a financial question, not a capacity question and (b) rush hour is when both finance and capacity collide. Public transport is a more efficient option per passenger-kilometre and per square metre of road or cubic metre of tunnel than self-driving cars. It is always going to be. Self-driving cars will have other virtues and will reshape transportation, but ascribing magical powers to them does nobody any good, especially if it leads to defunding of subways and buses.
treis 8y ago
>A standard R160 subway car carries up to about 250 people in an area that would be about the same as 5 Corollas positioned nose to tail, a starting ratio of about 10:1. If cars are made twice as dense, it's still 5:1. You're not accounting for the space between trains. They will only take up 5-10% of the available rail space because you need gaps between the trains.
- vkou 8y ago
  You need gaps between cars, too. Two seconds of following distance in good weather conditions, four seconds of following distance in bad weather conditions. At highway speeds, 4 seconds of following distance is 120 meters.
- jacques_chester 8y ago
  > You're not accounting for the space between trains. NYC's least efficient system is block train control, requiring 300M separation between trains. In 300M you can fit about 66 Corollas, again packed bumper to bumper. That's 66 * 5 people = 330 people, or approximately 1.5 subway cars. Subway trains are 6 or 8 subway cars long, depending on track and time of day. With CTBC some platforms can run at 60 trains per hour (30 local, 30 express). That's 8 subway cars every 2 minutes, or approximately 1,000 people per minute. To move 1,000 people at all with the Corollas you will need 250 * 4.55M of them, or approximately 1.1 kilometres of cars, bumper to bumper.
  - treis 8y ago
    >With CTBC some platforms can run at 60 trains per hour (30 local, 30 express). That's 8 subway cars every 2 minutes, or approximately 1,000 people per minute. Unless your trains are going at 10 kph you will have more of a gap than 300 meters if you see a train every 2 minutes.
    - jacques_chester 8y ago
      Or the trains can move much faster and much closer because of improved control. You should recognise this argument: it's the same logic given for why self-driving will solve everything.

davnicwil 8y ago

Yes you're absolutely correct - I guess my main question is could the space savings, like the pollution savings, be 'good enough' for it not to matter in practice, assuming that driverless cars become the 80% usecase for road traffic and today's 'massive 5 seater car for an average of 2 people' model goes away. It's also important to point out that of course, buses and trains shouldn't go away - they could indeed also have a bunch of problems solved by being self driving too, most notably the 24/7 running thing - they'd just be another option in the mix.

rhacker 8y ago

> Public transport will always be able to pack more people into the same space. While that's true, that's also just an argument for something we already understand. Are there possible arguments to be made about the number of busses and routes because it's not taking people point to point. What about the lul-time of day, where on-demand model is more efficient than driving empty busses around. They reduce schedules obviously. But now you're punishing passengers that start a shift at noon. There are more things to solve than just "the least amount of pollution and space." Totally unrelated but similar argument. The FAA introduced a new system and process for creating standard flight paths a few years ago. Flights around the nation started doing new things. TONS of people are now inundated by jet noise. They're now discussing just going back in certain areas to the old routes. They ONLY optimized for efficiency of route and didn't consider anything else.

jacques_chester 8y ago
> There are more things to solve than just "the least amount of pollution and space." The argument I was responding to was that self-driving cars would be sufficiently more efficient users of space that it would obviate the need for public transport. This was demonstrably false. > But now you're punishing passengers that start a shift at noon. Sure, but (a) that's a financial question, not a capacity question and (b) rush hour is when both finance and capacity collide. Public transport is a more efficient option per passenger-kilometre and per square metre of road or cubic metre of tunnel than self-driving cars. It is always going to be. Self-driving cars will have other virtues and will reshape transportation, but ascribing magical powers to them does nobody any good, especially if it leads to defunding of subways and buses.

treis 8y ago

>A standard R160 subway car carries up to about 250 people in an area that would be about the same as 5 Corollas positioned nose to tail, a starting ratio of about 10:1. If cars are made twice as dense, it's still 5:1. You're not accounting for the space between trains. They will only take up 5-10% of the available rail space because you need gaps between the trains.

vkou 8y ago
You need gaps between cars, too. Two seconds of following distance in good weather conditions, four seconds of following distance in bad weather conditions. At highway speeds, 4 seconds of following distance is 120 meters.
jacques_chester 8y ago
> You're not accounting for the space between trains. NYC's least efficient system is block train control, requiring 300M separation between trains. In 300M you can fit about 66 Corollas, again packed bumper to bumper. That's 66 * 5 people = 330 people, or approximately 1.5 subway cars. Subway trains are 6 or 8 subway cars long, depending on track and time of day. With CTBC some platforms can run at 60 trains per hour (30 local, 30 express). That's 8 subway cars every 2 minutes, or approximately 1,000 people per minute. To move 1,000 people at all with the Corollas you will need 250 * 4.55M of them, or approximately 1.1 kilometres of cars, bumper to bumper.
- treis 8y ago
  >With CTBC some platforms can run at 60 trains per hour (30 local, 30 express). That's 8 subway cars every 2 minutes, or approximately 1,000 people per minute. Unless your trains are going at 10 kph you will have more of a gap than 300 meters if you see a train every 2 minutes.
  - jacques_chester 8y ago
    Or the trains can move much faster and much closer because of improved control. You should recognise this argument: it's the same logic given for why self-driving will solve everything.