4 ms·

With autonomous vehicles, will subways matter in 5–10? I can imagine a world where we have small and very low cost electric transportation pods (no need for mos

With autonomous vehicles, will subways matter in 5–10? I can imagine a world where we have small and very low cost electric transportation pods (no need for most safety feature) that drive bumper to bumper, door handle to door handle at least on some routes. Cost per mile will be much cheaper than the subway.

Demoneeri 9y ago
It's a geometry problem, you don't have enough space in a city to have all those pods and pods station.
mbreese 9y ago
You can still only fit so many cars safely on a given road, regardless of how automated they are. Subways (and all public transportation) will always have greater potential throughput, provided that people can get where they want to go. The larger the city, the more likely you are to have common routes with other people. It's analogous to small packets vs jumbo packets. You're going to always have better throughput for the overhead, the larger the unit... so for just bulk moving of data (people) to/from a limited number of destinations, you'd be better served with the "jumbo" option. If you have a small number of people with a large number of destinations, a smaller option (cars), is better. Unless we're talking completely reimagining the transportation network (which isn't a 5-10 year time frame project), you won't see use of autonomous pods displace subways -- especially in a place like NYC.
skrause 9y ago
How do cyclists and pedestrians fit into that? Is this your utopia? https://i.ytimg.com/vi/s-kdRdzxdZQ/maxresdefault.jpg https://i.ytimg.com/vi/s-kdRdzxdZQ/maxresdefault.jpg
nerfhammer 9y ago
A single New York subway train can carry 1000-2000 people and might carry 2500 at rush hour. There are ~14000 licensed taxis in New York. So all of the taxis in New York could carry the equivalent of 5.6 trains. Any given subway line has about 15 trains per hour and there are 25 or so subway lines. So you could assume there's maybe 350 trains running at any given time vs. 5.6 train-equivalents in taxi space. So unless self-driving pods can somehow squeeze together 60 times more densely than taxis as well as not need to deal with crosswalks or traffic lights, the subway has a rather large advantage here. https://www.quora.com/How-many-people-are-on-New-York-subways-at-a-time https://www.quora.com/How-many-people-are-on-New-York-subway... https://www.quora.com/How-many-trains-are-on-a-New-York-subway-line-at-any-given-time https://www.quora.com/How-many-trains-are-on-a-New-York-subw... https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_services#Trains_per_hour https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_s...
- martinald 9y ago
  Keep in mind 15trains per hour is really quite poor by international standards. Victoria line in London can do 34 trains per hour currently and there is a plan to get it to 36 (anything further is really difficult because you hit a physical limitation of getting people on and off trains).
  - nerfhammer 9y ago
    But as many as 3-4 lines run on the same tracks/platforms mostly in Manhattan with some running local vs express. It's usually at least 4 platforms in a station, with 1x express and 1x local in both directions. Remember, it's mostly quadruple track. So it's actually more like 45/hour for express stops.
    - martinald 9y ago
      45/hour/track? Literally impossible even with world class signalling, which the NY Subway definitely does not have. 38 tph seems to be the physical limit. AFIAK only the L train reaches anywhere near "world class" capacity (as it has CBTC), but is still only 26tph. Other lines on the NY subway must be far less than that. From my experience 3-4 min headways per track are pretty common, which equates to 15-20tph. Obviously if you have both express and local then you're up to 30-40, but it could be ~double that with modern CBTC.
      - nerfhammer 9y ago
        If you look here: https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_services#Trains_per_hour https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_s... The lines with the same colors run on top of each other in Manhattan so you have to sum them. Supposedly the 456 does get 44/hour, counting express and local tracks together. I agree that most lines do not have modern signaling and most do not run at 45/hour most of the time. But also you know, 24x7 and all that.
        9y ago
krschultz 9y ago
Why do you think cost per mile would be cheaper than the subway? With CBTC (existing technology, though not rolled out to most of the subway) and intrusion detection, we don't need any labor on a subway. What's less expensive to maintain, a 10 subway car set that carries 1500 people or 1500 pods? Maybe paved roads are cheaper to maintain than subway track, but that's hard to really compare apples to apples. Honestly, I find it easier to imagine a NYC where there are no private vehicles allowed at all during rush hour than I find it possible to imagine one w/o subways.

Demoneeri 9y ago

It's a geometry problem, you don't have enough space in a city to have all those pods and pods station.

mbreese 9y ago

You can still only fit so many cars safely on a given road, regardless of how automated they are. Subways (and all public transportation) will always have greater potential throughput, provided that people can get where they want to go. The larger the city, the more likely you are to have common routes with other people. It's analogous to small packets vs jumbo packets. You're going to always have better throughput for the overhead, the larger the unit... so for just bulk moving of data (people) to/from a limited number of destinations, you'd be better served with the "jumbo" option. If you have a small number of people with a large number of destinations, a smaller option (cars), is better. Unless we're talking completely reimagining the transportation network (which isn't a 5-10 year time frame project), you won't see use of autonomous pods displace subways -- especially in a place like NYC.

skrause 9y ago

How do cyclists and pedestrians fit into that? Is this your utopia? https://i.ytimg.com/vi/s-kdRdzxdZQ/maxresdefault.jpg https://i.ytimg.com/vi/s-kdRdzxdZQ/maxresdefault.jpg

nerfhammer 9y ago

A single New York subway train can carry 1000-2000 people and might carry 2500 at rush hour. There are ~14000 licensed taxis in New York. So all of the taxis in New York could carry the equivalent of 5.6 trains. Any given subway line has about 15 trains per hour and there are 25 or so subway lines. So you could assume there's maybe 350 trains running at any given time vs. 5.6 train-equivalents in taxi space. So unless self-driving pods can somehow squeeze together 60 times more densely than taxis as well as not need to deal with crosswalks or traffic lights, the subway has a rather large advantage here. https://www.quora.com/How-many-people-are-on-New-York-subways-at-a-time https://www.quora.com/How-many-people-are-on-New-York-subway... https://www.quora.com/How-many-trains-are-on-a-New-York-subway-line-at-any-given-time https://www.quora.com/How-many-trains-are-on-a-New-York-subw... https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_services#Trains_per_hour https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_s...

martinald 9y ago
Keep in mind 15trains per hour is really quite poor by international standards. Victoria line in London can do 34 trains per hour currently and there is a plan to get it to 36 (anything further is really difficult because you hit a physical limitation of getting people on and off trains).
- nerfhammer 9y ago
  But as many as 3-4 lines run on the same tracks/platforms mostly in Manhattan with some running local vs express. It's usually at least 4 platforms in a station, with 1x express and 1x local in both directions. Remember, it's mostly quadruple track. So it's actually more like 45/hour for express stops.
  - martinald 9y ago
    45/hour/track? Literally impossible even with world class signalling, which the NY Subway definitely does not have. 38 tph seems to be the physical limit. AFIAK only the L train reaches anywhere near "world class" capacity (as it has CBTC), but is still only 26tph. Other lines on the NY subway must be far less than that. From my experience 3-4 min headways per track are pretty common, which equates to 15-20tph. Obviously if you have both express and local then you're up to 30-40, but it could be ~double that with modern CBTC.
    - nerfhammer 9y ago
      If you look here: https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_services#Trains_per_hour https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_s... The lines with the same colors run on top of each other in Manhattan so you have to sum them. Supposedly the 456 does get 44/hour, counting express and local tracks together. I agree that most lines do not have modern signaling and most do not run at 45/hour most of the time. But also you know, 24x7 and all that.
      - 9y ago

krschultz 9y ago

Why do you think cost per mile would be cheaper than the subway? With CBTC (existing technology, though not rolled out to most of the subway) and intrusion detection, we don't need any labor on a subway. What's less expensive to maintain, a 10 subway car set that carries 1500 people or 1500 pods? Maybe paved roads are cheaper to maintain than subway track, but that's hard to really compare apples to apples. Honestly, I find it easier to imagine a NYC where there are no private vehicles allowed at all during rush hour than I find it possible to imagine one w/o subways.