4 ms·

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

• 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.
  • mafribe 11y ago
    underestimate the practical difficulties My point is not that this is easy/hard, but rather: it's easier to provide top notch infra structure for the worlds population if it is concentrated in a few dense urban centres, rather than spread out. I find this hard to contest. Just think about distance, bearing in mind that the cost of sewage systems, rail (over- and underground), fibre-optic cables and so on basically tracks distance. if you split everyone into groups of 200k to 2m This is an interesting point. B b b but ... I cannot think of an existing city with 200k inhabitants and great infrastructure. I can't even think of a city with 2m inhabitants whose infrastructure can compete with world leaders such as Tokio, Manhattan, Hong Kong and the like. And even in these places the best infrastructure is found in the densest parts of the city, not in the outskirts. Note that the cities you have in mind, say European cities of 200k - 1m size, are rather spread out, and low density. I have lived in enough of those. But it would be really interesting to have cities that have 200k - 1m inhabitants and are extremely dense like central Hong Kong. Such small cities may be big and dense enough to have the economies of scale of their larger rivals. But, as pointed out by "vidarh", they would not remotely match megacities in terms of interesting cultural life. not a hypothetical, I don't think it works that well. European cities of 200k - 2m are car-centric in my experience. I supect China would run into major problems if its population live in low-density European style cities with 200k inhabitants each.
    • vidarh 11y ago
      > But it would be really interesting to have cities with that have 200k - 1m inhabitants and are extremely dense like central Hong Kong. They may be big and dense enough to have the economies of scale of their larger rivals. But, as pointed out by "vidarh", they would not remotely match megacities in terms of interesting cultural life. I think with that kind of density, if you go to 1m-2m size, you have a sufficient base for very regular high capacity public transport to other similar sized high density cities very near. E.g. Macau fascinates me (though I've never visited). It's a fairly small city - roughly 643,100 people (2015 estimate) - , yet it's spread out over a positively tiny area - about 30km^2. Overall density of 18,568/km2. If you condensed London into smaller cities with that density, you could have e.g. split London into four cities of about 120km^2 each, and still free up more than 1000km^2 for green belts or low density zones around them, and yet they'd still be near enough to each other for it be pretty much as easy to travel between the areas as today, and the increased density in each city might even cut down total travel times in many cases. The biggest challenge with something like that would be disciplined planning, beause obviously if you put big, dense cities like that near each other, the land in between would become immensely desirable.
• 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.