What do you mean when you say it "doesn't scale?" * Seoul has twice the population density of LA. * Seoul has less than half the number of road fatalities per

What do you mean when you say it "doesn't scale?" * Seoul has twice the population density of LA. * Seoul has less than half the number of road fatalities per 100,000 people. The point about "not a fast way to travel" is interesting but it's also worth recognizing that with double the population density there are twice as many destinations to visit, so that can be deceptive when you look at trip length. If there are 5 grocery stores within 5km vs. 5 grocery stores within 10km, it doesn't matter at all if it takes twice as long to travel 5km in the former case, it's equivalent. (And it's more likely you can do it on foot, which is healthier in terms of lower pollution, more exercise, and fewer road fatalities.)