4 ms·

Density alone is not an argument for mega-cities, though. While it's possible that the economies of scale keep increasing with size -- ie. maybe the electrical

by morsch 11y ago

Density alone is not an argument for mega-cities, though. While it's possible that the economies of scale keep increasing with size -- ie. maybe the electrical network of a dense city of 5 million people is more efficient than that of a dense city of 100k people -- there is probably a point somewhere between those two points where the gains are only marginal. A dense city of a 100k can support an excellent bus network, a dense city of 250k can additionaly support an excellent networks of trams or subways. 500k gets you direct access to high speed rail and beyond that I'm not sure what additional millions get you in terms of public transport -- an airport, I guess. And a dense city of 100k people is more walkable than a dense city of millions: In the former case, you can pretty much reach the whole city area by walking (if you are a healthy adult). In the latter, you can only walk in your general neighbourhood -- which probably ends up being much like a city of 100k itself, meaning you rarely have to venture outside for everyday needs (shopping, services, culture, even your job if you're lucky).

mafribe 11y ago
there is probably a point somewhere between those two points where the gains are only marginal. I think we have not reached it in any city currently on earth. I think the whole earth's population could live in a space the size e.g. of Texas, if that space was as densely populated as London (which is not that dense). In such a scenario it would be near trivial to provide everybody with top-notch public transport, waste disposal and so on. In the latter, you can only walk in your general neighbourhood That's true, but why is this a problem? For a sustainable, walkable city it's only relevant that all key infrastructure (e.g. schools, shopping, leisure, parks ...) is within walking distance and this infrastructure gets replicated in bigger cities.
- morsch 11y ago
  Of course there exist many places where we have not reached the point of marginal gains (and hence massive room for improvement), but you don't make an argument why you think we haven't reached that point anywhere on Earth. I think you underestimate the practical difficulties of providing 7 billion people with top-notch public transport and other public services, and there is no precedent of what a region the size of Texas with an average density of 10k/km2 would even look like (though there are artists' renditions, most of them dystopian). But anyway, if that could be done, it could just as well be done if you split everyone into groups of 200k to 2m and settled them in smaller regions of similar density. And that's not a hypothetical, that's what we call a city now, and they work fine. That's true, but why is this a problem? For a sustainable, walkable city it's only relevant that all key infrastructure (e.g. schools, shopping, leisure, parks ...) is within walking distance and this infrastructure gets replicated in bigger cities. I agree. I'm not saying that cities larger than 10m are a problem, per se, I'm just saying that smaller, dense cities get you most of the advantages from a quality of living and services aspect. I think it's a matter of taste whether you prefer to live in a city of 50k, 100k, 500k or 2m, and all of these are broadly similar in terms of sustainability.
  - vidarh 11y ago
    > I think you underestimate the practical difficulties of providing 7 billion people with top-notch public transport and other public services While some public transport issues increases with density (harder to e.g. dig new tunnels), one of the major issues with public transport at scale is the cost of laying rails and digging tunnels, and amortising those costs over larger populations makes it far more affordable. Once you have the rails, density means you can offer far more frequent service, which makes a huge difference to users. Being able to just assume there'll always be a train within a minute or two is a huge deal to get people to actually use public transport. Density also works the other way and reduces the need in many cases, as well as drop delivery costs and give new options (e.g. I can get stuff from one of the local Amazon competitors couriered over in 2 hours) that first become cost effective when density is high enough to create big enough markets. > (though there are artists' renditions, most of them dystopian) That may be so, but density to an extent also creates opportunity. E.g. my local road takes up roughly 45,000 square metres. Of this, roughly 1/3 is gardens where each family in effect only gets use of a very small portion, leaving many of them largely unused. Another roughly 1/3 is pavement, front yards mostly used for bins etc., and the road. Near our local station, new highrises are going up that will house almost the same number of people on a couple of thousand square metres of space. That's a lot of space freed up. In other words: The question is how far you want to go. If you slash space wasted on roads and wasted duplication, and increase heights, you can get massive increases in density almost everywhere and still end up with more desirable and practically usable space for most people to actually use for things other than transport that is only necessary due to the low density. If you go further than that, and take away all the green space etc., then yes, you get a dystopia. But you don't need to go very far. E.g. where I live is relatively average density for London. Increase the density of the London metro area five times, and you could empty the entirety of the rest of the UK into London. If every road like mine was replaced with high rises, you'd be able to achieve that with ease and still be left with vast empty tracts of land for new parks (and allotments for those who actually use their gardens today). London makes up well below 1% of the land area of the UK. I'm not suggesting it'd be a good idea to create a single megacity for the entire UK population. But achieving the density would free up huge amounts of land even if we set aside space for lots of big new parks. It'd also save vast amounts of energy used on transport by cutting distances for most travel.
- sologoub 11y ago
  London is 5100/sqkm, with 7.125 billion people, you'd need 1,397,059 sqkm, or 539,407 sq. miles. Texas is 268,820 sq. miles. You'd need higher density than Manhattan to fit all these people and have any hope of growth. Supplying such a monster would be a logistical miracle (or nightmare, depending on your perspective). Water alone would be extremely challenging - where are you going to get a steady supply and where can you store it?
- TheCoelacanth 11y ago
  There are cities that are much denser than London, though. For instance, Paris, or for a much more extreme example, Kowloon Walled City. Paris is probably not overly dense, but I think KWC definitely is.
vidarh 11y ago
I live in a London suburb. My suburb has about 300k. I can walk to the local town centre, three major train stations one of which is 20 minutes on the train from a major international airport. I can also walk to any number of tram stops, or take a bus. From the largest nearby stations, I can also reach central London in 15 minutes (two separate terminals), and any number of other city centres. The main difference with this vs. when I lived in Oslo, in a city of ~500k and a metro area of maybe 3-4 times that, is that in London I have the same amenities nearby, within walking distance or a short bus ride away, but I also have a vastly larger selection of all kinds of things: Tens of times as many theatres with accordingly larger selection; tens of times as many night clubs or bars; tens of times as many museums, most of which are larger, and many of which cover subjects not covered at all by museums in most smaller cities. In terms of business I have access to a pool of people that is tens of times larger, and equally a market within a range where I can get in a taxi to go see them face to face that is tens of times larger. That's what density brings. So yes, my local suburb is like a city. But I can pop over to any number of other places that are also like their own cities in 15-30 minutes, and that makes a big difference to having greater distances.

by morsch 11y ago

mafribe 11y ago

there is probably a point somewhere between those two points where the gains are only marginal. I think we have not reached it in any city currently on earth. I think the whole earth's population could live in a space the size e.g. of Texas, if that space was as densely populated as London (which is not that dense). In such a scenario it would be near trivial to provide everybody with top-notch public transport, waste disposal and so on. In the latter, you can only walk in your general neighbourhood That's true, but why is this a problem? For a sustainable, walkable city it's only relevant that all key infrastructure (e.g. schools, shopping, leisure, parks ...) is within walking distance and this infrastructure gets replicated in bigger cities.

morsch 11y ago
Of course there exist many places where we have not reached the point of marginal gains (and hence massive room for improvement), but you don't make an argument why you think we haven't reached that point anywhere on Earth. I think you underestimate the practical difficulties of providing 7 billion people with top-notch public transport and other public services, and there is no precedent of what a region the size of Texas with an average density of 10k/km2 would even look like (though there are artists' renditions, most of them dystopian). But anyway, if that could be done, it could just as well be done if you split everyone into groups of 200k to 2m and settled them in smaller regions of similar density. And that's not a hypothetical, that's what we call a city now, and they work fine. That's true, but why is this a problem? For a sustainable, walkable city it's only relevant that all key infrastructure (e.g. schools, shopping, leisure, parks ...) is within walking distance and this infrastructure gets replicated in bigger cities. I agree. I'm not saying that cities larger than 10m are a problem, per se, I'm just saying that smaller, dense cities get you most of the advantages from a quality of living and services aspect. I think it's a matter of taste whether you prefer to live in a city of 50k, 100k, 500k or 2m, and all of these are broadly similar in terms of sustainability.
- vidarh 11y ago
  > I think you underestimate the practical difficulties of providing 7 billion people with top-notch public transport and other public services While some public transport issues increases with density (harder to e.g. dig new tunnels), one of the major issues with public transport at scale is the cost of laying rails and digging tunnels, and amortising those costs over larger populations makes it far more affordable. Once you have the rails, density means you can offer far more frequent service, which makes a huge difference to users. Being able to just assume there'll always be a train within a minute or two is a huge deal to get people to actually use public transport. Density also works the other way and reduces the need in many cases, as well as drop delivery costs and give new options (e.g. I can get stuff from one of the local Amazon competitors couriered over in 2 hours) that first become cost effective when density is high enough to create big enough markets. > (though there are artists' renditions, most of them dystopian) That may be so, but density to an extent also creates opportunity. E.g. my local road takes up roughly 45,000 square metres. Of this, roughly 1/3 is gardens where each family in effect only gets use of a very small portion, leaving many of them largely unused. Another roughly 1/3 is pavement, front yards mostly used for bins etc., and the road. Near our local station, new highrises are going up that will house almost the same number of people on a couple of thousand square metres of space. That's a lot of space freed up. In other words: The question is how far you want to go. If you slash space wasted on roads and wasted duplication, and increase heights, you can get massive increases in density almost everywhere and still end up with more desirable and practically usable space for most people to actually use for things other than transport that is only necessary due to the low density. If you go further than that, and take away all the green space etc., then yes, you get a dystopia. But you don't need to go very far. E.g. where I live is relatively average density for London. Increase the density of the London metro area five times, and you could empty the entirety of the rest of the UK into London. If every road like mine was replaced with high rises, you'd be able to achieve that with ease and still be left with vast empty tracts of land for new parks (and allotments for those who actually use their gardens today). London makes up well below 1% of the land area of the UK. I'm not suggesting it'd be a good idea to create a single megacity for the entire UK population. But achieving the density would free up huge amounts of land even if we set aside space for lots of big new parks. It'd also save vast amounts of energy used on transport by cutting distances for most travel.
sologoub 11y ago
London is 5100/sqkm, with 7.125 billion people, you'd need 1,397,059 sqkm, or 539,407 sq. miles. Texas is 268,820 sq. miles. You'd need higher density than Manhattan to fit all these people and have any hope of growth. Supplying such a monster would be a logistical miracle (or nightmare, depending on your perspective). Water alone would be extremely challenging - where are you going to get a steady supply and where can you store it?
TheCoelacanth 11y ago
There are cities that are much denser than London, though. For instance, Paris, or for a much more extreme example, Kowloon Walled City. Paris is probably not overly dense, but I think KWC definitely is.

vidarh 11y ago

I live in a London suburb. My suburb has about 300k. I can walk to the local town centre, three major train stations one of which is 20 minutes on the train from a major international airport. I can also walk to any number of tram stops, or take a bus. From the largest nearby stations, I can also reach central London in 15 minutes (two separate terminals), and any number of other city centres. The main difference with this vs. when I lived in Oslo, in a city of ~500k and a metro area of maybe 3-4 times that, is that in London I have the same amenities nearby, within walking distance or a short bus ride away, but I also have a vastly larger selection of all kinds of things: Tens of times as many theatres with accordingly larger selection; tens of times as many night clubs or bars; tens of times as many museums, most of which are larger, and many of which cover subjects not covered at all by museums in most smaller cities. In terms of business I have access to a pool of people that is tens of times larger, and equally a market within a range where I can get in a taxi to go see them face to face that is tens of times larger. That's what density brings. So yes, my local suburb is like a city. But I can pop over to any number of other places that are also like their own cities in 15-30 minutes, and that makes a big difference to having greater distances.