6 ms·

I suspect that by the time we could build a high speed rail network in the US (say 30-40 years, minimum) autonomous vehicles on the freeway will be the superior

by vosper 9y ago

I suspect that by the time we could build a high speed rail network in the US (say 30-40 years, minimum) autonomous vehicles on the freeway will be the superior option. There's no fundamental reason that road vehicles couldn't exceed 200kph, just that humans are completely incapable of piloting safely at anywhere near those speeds. Once the need for a forward-looking pilot is gone you could design vehicles completely around the comfort of the occupants. And, better than HSR, the same vehicle can go door-to-door.

jacquesm 9y ago
> here's no fundamental reason that road vehicles couldn't exceed 200kph Actually, there is: energy costs for road traffic go up as the square of the velocity, for rail this is much better because there is only one (very aerodynamic) front section for as many carriages as you want to put behind the loc and steel-on-steel has much better rolling resistance than rubber-on-asphalt or concrete.
- vosper 9y ago
  That's a fair point, what's the energy cost of building thousands of miles of new railways, rather than using existing freeways? (okay, I'm being a little facetious) With regard to aerodynamics, I am assuming that following distances for advanced autonomous vehicles will be minimal. They could maybe drive bumper-to-bumper as long as all cars in the ... er ... train were similarly capable.
  - sangnoir 9y ago
    You'd want to physically couple those cars because should any one of them unexpectedly lose locomotion, they'll be a huge train wreck.
  - ocschwar 9y ago
    Track costs far less (in money and energy) to build and maintain than freeway.
    - CamperBob2 9y ago
      Unlike roads, fixed rail is virtually guaranteed not to be where you are, or to go where you want to go. There is a reason the US isn't well-connected by rail, and it has nothing to do with loony conspiracy theories about General Motors buying all the tracks up.
      - ocschwar 9y ago
        > Unlike roads, fixed rail is virtually guaranteed not to be where you are, or to go where you want to go. For no reason except the political. Go to any country in Europe, and you'll find that even the shopping malls have railway sidings and not just truck loading bays.
        CamperBob2 9y ago
        To us, 200 years seems like a long time. To you, 200 kilometers seems like a long distance.
        ocschwar 9y ago
        Dude, I'm American.
        CamperBob2 9y ago
        Then you should know why it's not practical to run rails to every grocery store and dry cleaner in every town in the US. I will never understand the obsession with fixed-rail transit on this site. It's interesting to observe, but it's never been satisfactorily explained. Is it just a matter of people never having been out of the Bay Area in their lives? In an age where personal mobility is becoming more important rather than less, when costs associated with large-scale civic construction projects have skyrocketed and completion times have come to be measured in decades, and when networked fleets of self-driving cars are almost literally just around the corner, rail transit in the general case is about the dumbest thing ever. But I recognize that this is essentially a religious argument, and that you're equally certain you're right. Not much we can do but vote accordingly, I guess.
- Numberwang 9y ago
  how about those volvo systems that line up auto cars behind each-other?
  - gsnedders 9y ago
    You still have induced drag from low pressure areas unless you design your cars so they're more box-like (i.e., the front of one car matches up with the rear of another, without any bonnet/hood/etc. or similar).
    - Numberwang 9y ago
      https://www.youtube.com/watch?v=GTJZEK4JP0k https://www.youtube.com/watch?v=GTJZEK4JP0k
- CamperBob2 9y ago
  There are so many opportunities to save energy with self-driving cars that I suspect this point will not be a clear win. But that assumes we do the right thing by constructing a standardized network and enforcing conformance with it, so they can behave more like high-speed train segments and less like individual vehicles. Here in the US, we generally do the right thing, but only after trying everything else first.
deleted 9y ago
[deleted]
zkms 9y ago
> There's no fundamental reason that road vehicles couldn't exceed 200kph There sorta is. Air resistance and tyre/pavement rolling resistance get mighty expensive at that sort of speed, and the need to carry along energy storage makes this even more problematic. High-speed rail vehicles amortise, over the whole train, the part of the drag that comes from the frontal area. Automobiles cannot do this. Once you've created a curve-free, very flat, grade-separated controlled access freeway for your 250kph cars, you've...got most of what you need for high-speed rail anyway. At that point you might as well just build some rails and overhead line and buy some TGV rolling stock.
Tiktaalik 9y ago
Autonomous vehicles won't be superior to high speed rail due to much worse space efficiency and induced demand putting a strain on road infrastructure. Even if autonomous cars are smaller than the ones we have now, they still take up too much space. Autonomous cars will expand the amount of drivers as one no longer needs a license, and the amount of cars will increase. This new demand will cause increased road congestion unless an expensive expansion of the road network takes place, an we know from induced demand that road expansion doesn't fix congestion in the long term anyway. Automobile oriented infrastructure doesn't scale whether the cars are autonomous or not, and it's a bad idea to base the entire transportation system around them.
leemailll 9y ago
>There's no fundamental reason that road vehicles couldn't exceed 200kph Then a blown tire will be a deadly accident.
- adrianN 9y ago
  A blown tyre is probably deadly even at normal speeds of ~130km/h. They don't blow very often though.

by vosper 9y ago

jacquesm 9y ago

> here's no fundamental reason that road vehicles couldn't exceed 200kph Actually, there is: energy costs for road traffic go up as the square of the velocity, for rail this is much better because there is only one (very aerodynamic) front section for as many carriages as you want to put behind the loc and steel-on-steel has much better rolling resistance than rubber-on-asphalt or concrete.

vosper 9y ago
That's a fair point, what's the energy cost of building thousands of miles of new railways, rather than using existing freeways? (okay, I'm being a little facetious) With regard to aerodynamics, I am assuming that following distances for advanced autonomous vehicles will be minimal. They could maybe drive bumper-to-bumper as long as all cars in the ... er ... train were similarly capable.
- sangnoir 9y ago
  You'd want to physically couple those cars because should any one of them unexpectedly lose locomotion, they'll be a huge train wreck.
- ocschwar 9y ago
  Track costs far less (in money and energy) to build and maintain than freeway.
  - CamperBob2 9y ago
    Unlike roads, fixed rail is virtually guaranteed not to be where you are, or to go where you want to go. There is a reason the US isn't well-connected by rail, and it has nothing to do with loony conspiracy theories about General Motors buying all the tracks up.
    - ocschwar 9y ago
      > Unlike roads, fixed rail is virtually guaranteed not to be where you are, or to go where you want to go. For no reason except the political. Go to any country in Europe, and you'll find that even the shopping malls have railway sidings and not just truck loading bays.
      - CamperBob2 9y ago
        To us, 200 years seems like a long time. To you, 200 kilometers seems like a long distance.
        ocschwar 9y ago
        Dude, I'm American.
        CamperBob2 9y ago
        Then you should know why it's not practical to run rails to every grocery store and dry cleaner in every town in the US. I will never understand the obsession with fixed-rail transit on this site. It's interesting to observe, but it's never been satisfactorily explained. Is it just a matter of people never having been out of the Bay Area in their lives? In an age where personal mobility is becoming more important rather than less, when costs associated with large-scale civic construction projects have skyrocketed and completion times have come to be measured in decades, and when networked fleets of self-driving cars are almost literally just around the corner, rail transit in the general case is about the dumbest thing ever. But I recognize that this is essentially a religious argument, and that you're equally certain you're right. Not much we can do but vote accordingly, I guess.
Numberwang 9y ago
how about those volvo systems that line up auto cars behind each-other?
- gsnedders 9y ago
  You still have induced drag from low pressure areas unless you design your cars so they're more box-like (i.e., the front of one car matches up with the rear of another, without any bonnet/hood/etc. or similar).
  - Numberwang 9y ago
    https://www.youtube.com/watch?v=GTJZEK4JP0k https://www.youtube.com/watch?v=GTJZEK4JP0k
CamperBob2 9y ago
There are so many opportunities to save energy with self-driving cars that I suspect this point will not be a clear win. But that assumes we do the right thing by constructing a standardized network and enforcing conformance with it, so they can behave more like high-speed train segments and less like individual vehicles. Here in the US, we generally do the right thing, but only after trying everything else first.

deleted 9y ago

[deleted]

zkms 9y ago

> There's no fundamental reason that road vehicles couldn't exceed 200kph There sorta is. Air resistance and tyre/pavement rolling resistance get mighty expensive at that sort of speed, and the need to carry along energy storage makes this even more problematic. High-speed rail vehicles amortise, over the whole train, the part of the drag that comes from the frontal area. Automobiles cannot do this. Once you've created a curve-free, very flat, grade-separated controlled access freeway for your 250kph cars, you've...got most of what you need for high-speed rail anyway. At that point you might as well just build some rails and overhead line and buy some TGV rolling stock.

Tiktaalik 9y ago

Autonomous vehicles won't be superior to high speed rail due to much worse space efficiency and induced demand putting a strain on road infrastructure. Even if autonomous cars are smaller than the ones we have now, they still take up too much space. Autonomous cars will expand the amount of drivers as one no longer needs a license, and the amount of cars will increase. This new demand will cause increased road congestion unless an expensive expansion of the road network takes place, an we know from induced demand that road expansion doesn't fix congestion in the long term anyway. Automobile oriented infrastructure doesn't scale whether the cars are autonomous or not, and it's a bad idea to base the entire transportation system around them.

leemailll 9y ago

>There's no fundamental reason that road vehicles couldn't exceed 200kph Then a blown tire will be a deadly accident.

adrianN 9y ago
A blown tyre is probably deadly even at normal speeds of ~130km/h. They don't blow very often though.