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Is that actually true from a transportation physics perspective? I can’t imagine that a curved tram/train/etc. would be able to accelerate and decelerate as eff

Is that actually true from a transportation physics perspective? I can’t imagine that a curved tram/train/etc. would be able to accelerate and decelerate as efficiently as one on a straight path.

ashildr 3y ago
A tram or even regular trains would not have to be very fast for those distances and for faster trains we already have the technology to lean into curves - it‘s quite common in Europe. And why not build a radial subway to get on to the opposing side of a circular city? (And why build this nonsense in a desert at all?)
- deleted 3y ago
  [deleted]
dragonwriter 3y ago
Yeah, but it wouldn't have as far to go, since the maximum distance between any two stations is half as far on a ring city of circumference d as on a linear city of length d, and you can get even shorter if you cut across the ring. To get the same area, you'd have to have slightly more center-line circumference on a ring city as linear distance on a line, but even so your transit distances are going to be shorter on the ring.
- keiferski 3y ago
  Right but if the idea is to maximize the open space / city size while maintaining a fast transit system, then the line makes sense to me. I guess I don’t really understand the criticism, most of which seems to be “you should just build something that isn’t the thing you want to build.” There is plenty of aesthetic merit to the linear city idea on its own. To use an example of a place that already exists: the city Łódź in Poland is situated along a single linear 4-5km street. Other neighborhoods branch off from it, but essentially the main road is the city’s layout. I really like it and think it’s a lot more interesting than it would be as a circle, even if the transit is theoretically not as optimal. There is something very aesthetically appealing about it.
  - offices 3y ago
    >if the idea is to maximize the open space / city size while maintaining a fast transit system Then it's Goodhart law in action. A fast transit system is desirable because it's a proxy for low-friction travel. This has the speed and the friction.
  - StefanBatory 3y ago
    the city Łódź in Poland is situated along a single linear 4-5km street Piotrkowska?
    - keiferski 3y ago
      Yep. The city itself expands in all directions but Piotrowska is the main hub.
  - krisoft 3y ago
    > the city Łódź in Poland is situated along a single linear 4-5km street. Are we just making things up? Just by a single glance at a map of Łódź you can see that this is not true. The city is clearly blob shaped. > I guess I don’t really understand the criticism, most of which seems to be “you should just build something that isn’t the thing you want to build.” The criticism is that there are reasons why cities are built the way they are built. "Looks good on a 3d render" is not a great reason to do something, and the reasons the proponents list don't hold up to scrutiny.
    - keiferski 3y ago
      Had you taken more than a glance, you would have come across this: https://en.wikipedia.org/wiki/Piotrkowska_Street https://en.wikipedia.org/wiki/Piotrkowska_Street And yes, as I wrote, it is the main axis of the city, even if other neighborhoods branch off of it. This is a basic obvious fact about the city: From the very beginning this street was the central axis, around which the city grew bigger, and its development spontaneously gave the present shape to its centre. At first the city was mainly the highway, but later it changed into the city's showcase, the leisure and shopping centre, where the life of growing industrial agglomeration could be observed.
gaazoh 3y ago
Acceleration and deceleration aren't relevant here, the limit would be passenger comfort either way. Curved tracks do mean limits on top speed, as the centrifugal force needs to be kept below what would be uncomfortable for passengers. It also can cause some issues for building stations, as curved stations require a wider gap between the train and the platform. But neither is a blocking issue, all train tracks in the world do have curve, and curved stations aren't unusual in public transport systems. The grandparent probably means disk, not ring-shaped when mentioning circles anyway. Pick any 2 point at random into a 33km² circle, the average distance will be 4km, and worst case scenario 6km. Do the same thing in a 33km², 200m-wide "line", the average distance will be 85km, with a worst case of 170km. A circular city doesn't need nearly as much raw speed for it's public transport to be more efficient than transport in a nonsensical linear city could ever be, even if you throw in ridiculously fast trains and sprinkle magical AI thinking. It's not a coincidence that all major cities are roughly circular even though they are built around roughly linear features (navigable rivers and/or coast line). It's just what naturally works.
dkdbejwi383 3y ago
Acceleration etc wouldn't really matter if I live at one end of the line and my friend lives at the opposite end. It would be an annoyingly long journey that stops at every single other station in the entire city. In a regular city that grows outwards, you'd expect there to be circumferential routes as well as cross-city routes connecting various points, making the travel time more bearable.
- saberience 3y ago
  I sort of assume they would have express trains as well as local trains, a bit like the NY subway. I.e. one train which just goes direct to the other end with no stops at high speed.
  - pndy 3y ago
    Wikipedia article mentions "the Spine" - an underground tunnel that would host transport superfast train infrastructure connecting both sides of the complex. Traveling from one end to another would take 20mins, supposedly.
    - ta1243 3y ago
      So about as long as riding a bike from anywhere in a equivalent sized normal city to another point (6km tops)
- keiferski 3y ago
  It would matter if an express train could accelerate fast enough to make the end-to-end trip quicker than a cross-city trip in a typical city.
  - ta1243 3y ago
    No. With no top speed, accelerate for 85km at 1m/s then decelerate for the next 85km/s at 1m/s and that's about 13 minutes with a top speed of about 900mph. 1m/s is the top acceleration you can have for a typical passenger train for comfort purposes. Total area of a 170km*200m city is 34 square km, or a city about 6.5km across. London's Elizabeth line (crossrail) covers a distance of 6.75km from Paddington to Liverpool Street in 11 minutes, with 3 intermediate stops. The circumference of a 6.5km diameter city would be 20km. 20 cross-city lines with decent headway and interchange would give a worst case journey of - 250m to nearest station - 3 minutes walk - 2 minute wait for train - 5 minutes to central station - 200m/3 minutes to appropiate platform - 2 minute wait for train - 5 minutes to destination station - 200m/3 minutes to destination 25 minutes. From anywhere to anywhere.
wasmitnetzen 3y ago
The Line (full length) is supposed to have a footprint of 34km2, that's a circle with a diameter of 3.3km/2 miles. That's a bike-sized city. You can easily add 50% of parks and waterways to get to a nice city, that makes it 4km/2.5 miles. And you can still build mostly straight-line trams in a circle anyway.
Moldoteck 3y ago
circular/disk cities are basically line cities that are copied and rotated, you still can build straight line transport. If you talk about real circle cities and not disks-the idea is just as bad as straight line

Is that actually true from a transportation physics perspective? I can’t imagine that a curved tram/train/etc. would be able to accelerate and decelerate as efficiently as one on a straight path.

ashildr 3y ago

A tram or even regular trains would not have to be very fast for those distances and for faster trains we already have the technology to lean into curves - it‘s quite common in Europe. And why not build a radial subway to get on to the opposing side of a circular city? (And why build this nonsense in a desert at all?)

deleted 3y ago
[deleted]

dragonwriter 3y ago

Yeah, but it wouldn't have as far to go, since the maximum distance between any two stations is half as far on a ring city of circumference d as on a linear city of length d, and you can get even shorter if you cut across the ring. To get the same area, you'd have to have slightly more center-line circumference on a ring city as linear distance on a line, but even so your transit distances are going to be shorter on the ring.

keiferski 3y ago
Right but if the idea is to maximize the open space / city size while maintaining a fast transit system, then the line makes sense to me. I guess I don’t really understand the criticism, most of which seems to be “you should just build something that isn’t the thing you want to build.” There is plenty of aesthetic merit to the linear city idea on its own. To use an example of a place that already exists: the city Łódź in Poland is situated along a single linear 4-5km street. Other neighborhoods branch off from it, but essentially the main road is the city’s layout. I really like it and think it’s a lot more interesting than it would be as a circle, even if the transit is theoretically not as optimal. There is something very aesthetically appealing about it.
- offices 3y ago
  >if the idea is to maximize the open space / city size while maintaining a fast transit system Then it's Goodhart law in action. A fast transit system is desirable because it's a proxy for low-friction travel. This has the speed and the friction.
- StefanBatory 3y ago
  the city Łódź in Poland is situated along a single linear 4-5km street Piotrkowska?
  - keiferski 3y ago
    Yep. The city itself expands in all directions but Piotrowska is the main hub.
- krisoft 3y ago
  > the city Łódź in Poland is situated along a single linear 4-5km street. Are we just making things up? Just by a single glance at a map of Łódź you can see that this is not true. The city is clearly blob shaped. > I guess I don’t really understand the criticism, most of which seems to be “you should just build something that isn’t the thing you want to build.” The criticism is that there are reasons why cities are built the way they are built. "Looks good on a 3d render" is not a great reason to do something, and the reasons the proponents list don't hold up to scrutiny.
  - keiferski 3y ago
    Had you taken more than a glance, you would have come across this: https://en.wikipedia.org/wiki/Piotrkowska_Street https://en.wikipedia.org/wiki/Piotrkowska_Street And yes, as I wrote, it is the main axis of the city, even if other neighborhoods branch off of it. This is a basic obvious fact about the city: From the very beginning this street was the central axis, around which the city grew bigger, and its development spontaneously gave the present shape to its centre. At first the city was mainly the highway, but later it changed into the city's showcase, the leisure and shopping centre, where the life of growing industrial agglomeration could be observed.

gaazoh 3y ago

Acceleration and deceleration aren't relevant here, the limit would be passenger comfort either way. Curved tracks do mean limits on top speed, as the centrifugal force needs to be kept below what would be uncomfortable for passengers. It also can cause some issues for building stations, as curved stations require a wider gap between the train and the platform. But neither is a blocking issue, all train tracks in the world do have curve, and curved stations aren't unusual in public transport systems. The grandparent probably means disk, not ring-shaped when mentioning circles anyway. Pick any 2 point at random into a 33km² circle, the average distance will be 4km, and worst case scenario 6km. Do the same thing in a 33km², 200m-wide "line", the average distance will be 85km, with a worst case of 170km. A circular city doesn't need nearly as much raw speed for it's public transport to be more efficient than transport in a nonsensical linear city could ever be, even if you throw in ridiculously fast trains and sprinkle magical AI thinking. It's not a coincidence that all major cities are roughly circular even though they are built around roughly linear features (navigable rivers and/or coast line). It's just what naturally works.

dkdbejwi383 3y ago

Acceleration etc wouldn't really matter if I live at one end of the line and my friend lives at the opposite end. It would be an annoyingly long journey that stops at every single other station in the entire city. In a regular city that grows outwards, you'd expect there to be circumferential routes as well as cross-city routes connecting various points, making the travel time more bearable.

saberience 3y ago
I sort of assume they would have express trains as well as local trains, a bit like the NY subway. I.e. one train which just goes direct to the other end with no stops at high speed.
- pndy 3y ago
  Wikipedia article mentions "the Spine" - an underground tunnel that would host transport superfast train infrastructure connecting both sides of the complex. Traveling from one end to another would take 20mins, supposedly.
  - ta1243 3y ago
    So about as long as riding a bike from anywhere in a equivalent sized normal city to another point (6km tops)
keiferski 3y ago
It would matter if an express train could accelerate fast enough to make the end-to-end trip quicker than a cross-city trip in a typical city.
- ta1243 3y ago
  No. With no top speed, accelerate for 85km at 1m/s then decelerate for the next 85km/s at 1m/s and that's about 13 minutes with a top speed of about 900mph. 1m/s is the top acceleration you can have for a typical passenger train for comfort purposes. Total area of a 170km*200m city is 34 square km, or a city about 6.5km across. London's Elizabeth line (crossrail) covers a distance of 6.75km from Paddington to Liverpool Street in 11 minutes, with 3 intermediate stops. The circumference of a 6.5km diameter city would be 20km. 20 cross-city lines with decent headway and interchange would give a worst case journey of - 250m to nearest station - 3 minutes walk - 2 minute wait for train - 5 minutes to central station - 200m/3 minutes to appropiate platform - 2 minute wait for train - 5 minutes to destination station - 200m/3 minutes to destination 25 minutes. From anywhere to anywhere.

wasmitnetzen 3y ago

The Line (full length) is supposed to have a footprint of 34km2, that's a circle with a diameter of 3.3km/2 miles. That's a bike-sized city. You can easily add 50% of parks and waterways to get to a nice city, that makes it 4km/2.5 miles. And you can still build mostly straight-line trams in a circle anyway.

Moldoteck 3y ago

circular/disk cities are basically line cities that are copied and rotated, you still can build straight line transport. If you talk about real circle cities and not disks-the idea is just as bad as straight line