4 ms·

The problem is that 1 mile of rail can move a lot more passengers than 1 mile of road.

sixstringtheory 4y ago
What is the route capacity for a lane of freeway vs a rail line? I assumed it’s the opposite, since a freeway has continuous throughout while a rail line is discrete, but I don’t have a good intuition for comparing the scale of each mode.
- dragonwriter 4y ago
  > What is the route capacity for a lane of freeway vs a rail line? I assumed it’s the opposite, since a freeway has continuous throughout while a rail line is discrete According to this book (which provides assumptions and calculations supporting) [0], 10:1 in favor of rail, as a conservative estimate. https://eng.libretexts.org/Bookshelves/Industrial_and_Systems_Engineering/Book%3A_The_Art_of_Insight_in_Science_and_Engineering_(Mahajan)/01%3A_Part_I-_Organizing_Complexity/01%3A_Divide_and_Conquer/1.02%3A_Rails_vs_Roads#:~:text=How%20does%20the%20capacity%20of,capacity%20of%20a%20train%20line%3F&text=This%20capacity%20is%20ten%20times,single%20fast%2Dflowing%20highway%20lane https://eng.libretexts.org/Bookshelves/Industrial_and_System....
  - cyberax 4y ago
    > A rush-hour train may consist of 20 cars The author is smoking some hard crack.
    - AnimalMuppet 4y ago
      Well, BART has no problem running 9-car trains. I don't know if that's rush hour or not, but I've seen them. If the rest of the math is right, that still gets you 4.5-to-1 in favor of rail.
      - dragonwriter 4y ago
        BART (mainline) runs a maximum of 10 car trains, with a “crush” (maximum) capacity of 200+ per car.
      - cyberax 4y ago
        Have you ever walked past a 20-car train? It's way too long for commuting. There will be no way to build platforms for it unless you're doing a full green-field build.
      - snovv_crash 4y ago
        Europe has plenty of double-story trains. I agree 10 is about the limit otherwise the station sizes aren't people friendly.
        Symbiote 4y ago
        The Eurostar trains between London and Brussels/Paris/Amsterdam have 16-18 coaches, although they are noticeably long. (Other than night trains, I'd expect these to be the longest in Europe.)
- bluGill 4y ago
  How do you calculate capacity? Safety engineers keep yelling that drivers need to keep 3 seconds between cars, but in reality they most drive about .3 seconds from the car in front. There is nearly a 10x difference in freeway capacity between just those two. Trains tend to maintain longer distances, but if you want to ignore safety we can follow a lot closer.
- adgjlsfhk1 4y ago
  The big difference is that in a train, you fit 4 people wide and roughly 2-3 ft front to back per person while in cars which have average capacity of ~1.5 per car, you have 1.5 people wide and 50-200 ft front to back. Trains are farther apart than cars, but fit a ton of people per train.
cyberax 4y ago
The calculations on that page are not correct. First, the average car occupancy is not 1, it's 1.5 on average. Second, the lane capacity is 1900 cars per hour (that's maximum at around 45 mph, btw). So this works out to 8550 people per hour. A realistic scenario for commuter trains (that would replace a freeway) is 1 train every 10 minutes, and even this is pretty tough. So you have 6 trains per hour, and to match the throughput you'd need 1425 people per train. Most train platforms are maxed out at well below 10 cars (Caltrain is 6 cars), 20 car trains are just pure nonsense for commuting. So for 10 car trains it'll be around 150 people per car. Caltrain cars are 130 seats per car ( https://www.greencaltrain.com/2014/05/keeping-up-with-caltrain-capacity-needs/ https://www.greencaltrain.com/2014/05/keeping-up-with-caltra... ), with another 40 standing places. Basically, a perfectly run commuter train system is _just_ barely comparable with a regular 6-lane freeway. Sorry train fans, but trains are not that great for commuting.
- judge2020 4y ago
  Correction, trains specifically. Subways and light rail are immensely higher ROI (as in, benefit vs cost) within a city since it effectively forces people close together, while a 6-lane-on-each-side highway isn't economically feasible for all of the high-traffic areas.
- richardw 4y ago
  > Sorry train fans, but trains are not that great for commuting. Quick comparison: more people (3.6m) go through Shinjuku Station in Tokyo than the daytime population of Manhattan, at 3.1m. Only half of those travel into Manhattan, using all modes of transport. When things get extreme it’s hard to just double the road network and parking into a single location. https://en.m.wikipedia.org/wiki/Shinjuku_Station https://en.m.wikipedia.org/wiki/Shinjuku_Station
  - cyberax 4y ago
    This station is served by 12 lines. So presumably that's 24 tracks. This means that one track would need to carry a bit more than 150000 people a day on average. A 6-lane freeway can carry around 100000 people a day. As a sanity check, the infamous Katy Freeway carries 350000 cars a day, for about 600000 people. It's 14 main travel lanes wide. So yep, trains are not that efficient compared to freeways.

What is the route capacity for a lane of freeway vs a rail line? I assumed it’s the opposite, since a freeway has continuous throughout while a rail line is discrete, but I don’t have a good intuition for comparing the scale of each mode.

dragonwriter 4y ago
> What is the route capacity for a lane of freeway vs a rail line? I assumed it’s the opposite, since a freeway has continuous throughout while a rail line is discrete According to this book (which provides assumptions and calculations supporting) [0], 10:1 in favor of rail, as a conservative estimate. https://eng.libretexts.org/Bookshelves/Industrial_and_Systems_Engineering/Book%3A_The_Art_of_Insight_in_Science_and_Engineering_(Mahajan)/01%3A_Part_I-_Organizing_Complexity/01%3A_Divide_and_Conquer/1.02%3A_Rails_vs_Roads#:~:text=How%20does%20the%20capacity%20of,capacity%20of%20a%20train%20line%3F&text=This%20capacity%20is%20ten%20times,single%20fast%2Dflowing%20highway%20lane https://eng.libretexts.org/Bookshelves/Industrial_and_System....
- cyberax 4y ago
  > A rush-hour train may consist of 20 cars The author is smoking some hard crack.
  - AnimalMuppet 4y ago
    Well, BART has no problem running 9-car trains. I don't know if that's rush hour or not, but I've seen them. If the rest of the math is right, that still gets you 4.5-to-1 in favor of rail.
    - dragonwriter 4y ago
      BART (mainline) runs a maximum of 10 car trains, with a “crush” (maximum) capacity of 200+ per car.
    - cyberax 4y ago
      Have you ever walked past a 20-car train? It's way too long for commuting. There will be no way to build platforms for it unless you're doing a full green-field build.
    - snovv_crash 4y ago
      Europe has plenty of double-story trains. I agree 10 is about the limit otherwise the station sizes aren't people friendly.
      - Symbiote 4y ago
        The Eurostar trains between London and Brussels/Paris/Amsterdam have 16-18 coaches, although they are noticeably long. (Other than night trains, I'd expect these to be the longest in Europe.)
bluGill 4y ago
How do you calculate capacity? Safety engineers keep yelling that drivers need to keep 3 seconds between cars, but in reality they most drive about .3 seconds from the car in front. There is nearly a 10x difference in freeway capacity between just those two. Trains tend to maintain longer distances, but if you want to ignore safety we can follow a lot closer.
adgjlsfhk1 4y ago
The big difference is that in a train, you fit 4 people wide and roughly 2-3 ft front to back per person while in cars which have average capacity of ~1.5 per car, you have 1.5 people wide and 50-200 ft front to back. Trains are farther apart than cars, but fit a ton of people per train.

cyberax 4y ago

The calculations on that page are not correct. First, the average car occupancy is not 1, it's 1.5 on average. Second, the lane capacity is 1900 cars per hour (that's maximum at around 45 mph, btw). So this works out to 8550 people per hour. A realistic scenario for commuter trains (that would replace a freeway) is 1 train every 10 minutes, and even this is pretty tough. So you have 6 trains per hour, and to match the throughput you'd need 1425 people per train. Most train platforms are maxed out at well below 10 cars (Caltrain is 6 cars), 20 car trains are just pure nonsense for commuting. So for 10 car trains it'll be around 150 people per car. Caltrain cars are 130 seats per car ( https://www.greencaltrain.com/2014/05/keeping-up-with-caltrain-capacity-needs/ https://www.greencaltrain.com/2014/05/keeping-up-with-caltra... ), with another 40 standing places. Basically, a perfectly run commuter train system is _just_ barely comparable with a regular 6-lane freeway. Sorry train fans, but trains are not that great for commuting.

judge2020 4y ago
Correction, trains specifically. Subways and light rail are immensely higher ROI (as in, benefit vs cost) within a city since it effectively forces people close together, while a 6-lane-on-each-side highway isn't economically feasible for all of the high-traffic areas.
richardw 4y ago
> Sorry train fans, but trains are not that great for commuting. Quick comparison: more people (3.6m) go through Shinjuku Station in Tokyo than the daytime population of Manhattan, at 3.1m. Only half of those travel into Manhattan, using all modes of transport. When things get extreme it’s hard to just double the road network and parking into a single location. https://en.m.wikipedia.org/wiki/Shinjuku_Station https://en.m.wikipedia.org/wiki/Shinjuku_Station
- cyberax 4y ago
  This station is served by 12 lines. So presumably that's 24 tracks. This means that one track would need to carry a bit more than 150000 people a day on average. A 6-lane freeway can carry around 100000 people a day. As a sanity check, the infamous Katy Freeway carries 350000 cars a day, for about 600000 people. It's 14 main travel lanes wide. So yep, trains are not that efficient compared to freeways.