5 ms·

I've been thinking about this a lot and think there's a few things to think about. First, the reason we haven't seen these is because until very recently the t

I've been thinking about this a lot and think there's a few things to think about. First, the reason we haven't seen these is because until very recently the tech needed to make them cheap wasn't there. Second, the technology seems to be caught a classic "worse is better" situation. The actual PRT tech is clearly superior to buses and LRTs, but those are well understood and there's a simple evolutionary path (car, bus, bus lane, lrt, lrt lane, subway). PRTs require a leap of thinking from people and governments don't have any incentives or mandate to take such risks. Third, PRTs tracks may be hard to connect to a true network where pods seamlessly switch between tracks. Finally, the self driving car could very well kill this in its tracks, but no form of transport can deliver speed or consistency without a dedicated right of way, be that suspended track, tunnel, marked lane etc.

anon4 11y ago
This is just rail with person-sized vehicles. Maybe you can dub it "modular rail" to make it easier for people to grok, but it's not that weird. Also, you could have them run on the existing subway system and just build off-line stations. Though before you do that, you should take into consideration designing the pods so I can take my bicycle on it, or my dog, etc.
rm_-rf_slash 11y ago
Self-driving cars will likely kill PRT ambitions by being a better band-aid for long enough to not have to think about the problem for a while, like how successive attempts at solar power were buried for more than 100 years by more efficient coal extraction, then oil, then nuclear, then oil, again.
- eridius 11y ago
  Self-driving cars aren't a band-aid. In the long term, where every vehicle on the road is self-driving, then they're the best solution possible (for any travel distance that doesn't warrant something like Hyperloop / planes / trains). I say this because self-driving cars can go everywhere (that cars can go). Pods have a fixed track, they can only go where there's track to go. The only way for Pods to be better than self-driving cars is if we rip up all the roads and replace the entire road network with a pod track network, but that obviously will never happen (and even then it's not necessarily better, because a pod track network could only be used for pods, but roads can be used by a lot more than just cars).
  - rm_-rf_slash 11y ago
    Of course self-driving cars are the necessary future, but it will drastically increase ridership as it becomes so much more convenient than the alternatives (including being sober/awake enough to drive). Over time I suspect that even the most efficient car system will result in traffic sucking just as much today, except with the option to watch tv instead of the road.
  - Zach_the_Lizard 11y ago
    Self-driving cars would still be less workable than rail when there's a certain level of density. I can't see New Yorkers all loading up in self driving cars; they just don't scale as well as trains do. Even assuming quadruple capacity from the roads, you would still need a large number of fairly beefy bridges and tunnels to get everyone coming from outside of Manhattan into Manhattan.
    - eridius 11y ago
      Oh sure, there's still a need for high-capacity mass transit options. But mass transit cannot go everywhere (or even most places). My argument here is strictly about personal transport (which is what Pods are).
    - nulltype 11y ago
      In what way do they not scale as well as trains do? I think self driving cars will probably introduce a huge pile of problems, but that particular claim seems odd to me.
      - Zach_the_Lizard 11y ago
        It comes down to space. Cars occupy way more space per passenger than trains do. A fully loaded subway train can easily carry almost thousand people. The 7000 series in the DC Metro carries ~175 people per car maximum, and the trains are 8 cars long, for 1400 people per train. Normally, 26 trains per hour are scheduled during rush hour, allowing up to 36,000 people per hour if all trains were 8 cars long (they currently aren't due to power constraints). Other systems that have longer trains, better headways, and better seat configurations have way higher capacities. New York for instance could achieve much greater capacity given its longer trains and a modern signalling system. By contrast, a road lane (which uses the same space) currently typically carries around 1000-2000 cars per hour. In ideal circumstances it can be almost 5000 cars per hour. Even assuming quadruple capacity from self driving cars (not realistic), 20,000 cars per hour in ideal circumstances would compete with trains at a far higher environmental cost. But in more realistic scenarios with quadruple capacity, 4000-8000 cars per hour would fall way short of a train. Given that we have to account for pedestrians, cyclists, etc., I can easily see traffic lights continuing to exist, making self driving cars not achieve the miracles people expect.

anon4 11y ago

This is just rail with person-sized vehicles. Maybe you can dub it "modular rail" to make it easier for people to grok, but it's not that weird. Also, you could have them run on the existing subway system and just build off-line stations. Though before you do that, you should take into consideration designing the pods so I can take my bicycle on it, or my dog, etc.

rm_-rf_slash 11y ago

Self-driving cars will likely kill PRT ambitions by being a better band-aid for long enough to not have to think about the problem for a while, like how successive attempts at solar power were buried for more than 100 years by more efficient coal extraction, then oil, then nuclear, then oil, again.

eridius 11y ago
Self-driving cars aren't a band-aid. In the long term, where every vehicle on the road is self-driving, then they're the best solution possible (for any travel distance that doesn't warrant something like Hyperloop / planes / trains). I say this because self-driving cars can go everywhere (that cars can go). Pods have a fixed track, they can only go where there's track to go. The only way for Pods to be better than self-driving cars is if we rip up all the roads and replace the entire road network with a pod track network, but that obviously will never happen (and even then it's not necessarily better, because a pod track network could only be used for pods, but roads can be used by a lot more than just cars).
- rm_-rf_slash 11y ago
  Of course self-driving cars are the necessary future, but it will drastically increase ridership as it becomes so much more convenient than the alternatives (including being sober/awake enough to drive). Over time I suspect that even the most efficient car system will result in traffic sucking just as much today, except with the option to watch tv instead of the road.
- Zach_the_Lizard 11y ago
  Self-driving cars would still be less workable than rail when there's a certain level of density. I can't see New Yorkers all loading up in self driving cars; they just don't scale as well as trains do. Even assuming quadruple capacity from the roads, you would still need a large number of fairly beefy bridges and tunnels to get everyone coming from outside of Manhattan into Manhattan.
  - eridius 11y ago
    Oh sure, there's still a need for high-capacity mass transit options. But mass transit cannot go everywhere (or even most places). My argument here is strictly about personal transport (which is what Pods are).
  - nulltype 11y ago
    In what way do they not scale as well as trains do? I think self driving cars will probably introduce a huge pile of problems, but that particular claim seems odd to me.
    - Zach_the_Lizard 11y ago
      It comes down to space. Cars occupy way more space per passenger than trains do. A fully loaded subway train can easily carry almost thousand people. The 7000 series in the DC Metro carries ~175 people per car maximum, and the trains are 8 cars long, for 1400 people per train. Normally, 26 trains per hour are scheduled during rush hour, allowing up to 36,000 people per hour if all trains were 8 cars long (they currently aren't due to power constraints). Other systems that have longer trains, better headways, and better seat configurations have way higher capacities. New York for instance could achieve much greater capacity given its longer trains and a modern signalling system. By contrast, a road lane (which uses the same space) currently typically carries around 1000-2000 cars per hour. In ideal circumstances it can be almost 5000 cars per hour. Even assuming quadruple capacity from self driving cars (not realistic), 20,000 cars per hour in ideal circumstances would compete with trains at a far higher environmental cost. But in more realistic scenarios with quadruple capacity, 4000-8000 cars per hour would fall way short of a train. Given that we have to account for pedestrians, cyclists, etc., I can easily see traffic lights continuing to exist, making self driving cars not achieve the miracles people expect.