One problem. River ravines and large parks (IE. High Park, Toronto Zoo) would have a low density, but a larger bicycle use.

Makes sense now that I think of the fact that Atlanta is known as the "city in a forest" and is said to have more tree canopy cover than other US cities. Though then again, to be fair, lots of cities, including Toronto itself as seen on those park signs, like to call themselves "city in a park" or "city in a garden", as in the case of Philly or Chicago (and of course New Jersey being the "Garden state") and are also fairly dense.

The median for Singapore is about 3,900 people per subzone, with a median area of about 1.23 km^2. That said, the population in these subzones varies much more than the US census tracts -- some subzones have as many as 70-120,000 people, whereas many others have a population of zero (like the Central Water Catchment subzone which is some 65 km^2). However, within each neighborhood density doesn't vary as much as in the Americas -- many of these subzones are essentially a cluster of high-rises, with the park next to those high-rises being a subzone of it's own. Macau's neighborhoods used to calculate weighted density are pretty large -- the smallest one has 9,300 people, the median around 50,000 people, and the largest one has 237,500 people. Despite those large neighborhood sizes, it STILL has a weighted density of above 67,000 per sq km. So Macau is dense. As for Hong Kong, I could not find shape files for the precinct equivalent data and had to use the larger districts. Many of these districts have a ton of completely uninhabited land in them as well as extremely dense settlements, and I removed the uninhabited land and then did some back-of-the-envelope adjusting for variations in the populated area densities to come up with my figure. Macau is very similar to Hong Kong in terms of density, with similar space constraints, so the fact that the Hong Kong figure is in the ballpark of Macau (but slightly less) seems fairly logical. On tree cover -- according to this source, Atlanta has the most tree cover of any US city at 36.7% (note that this is the city only and not the metropolitan area). That may seem to explain why it's so un-dense, except when you consider that Boston has 29% tree cover and New York City has 24% tree cover. Philly and Chicago (where I'm from) actually have among the lowest tree covers at 15.7% and 11% respectively, so it seems like those "city in a garden" monikers are misnomers.

Calgary Urban Area (using US Census Bureau Criteria) 2016 Population: 1,244,345 Weighted Density: 7,572 ppsm Compared to previous years 2011: 7,228 ppsm 2006: 6,488 ppsm

These numbers just remind me one thing: most cities are really not dense. The French city I live in has a density of 9000/sq km in the city proper, which is more than twice the density of Toronto, even denser the the old Toronto. Yesterday I took a long walk, and merely less than 30 minutes on foot from the centre it becomes noticeably not dense - gaps between buildings get bigger and height of buildings declining, with more and more open space and more and more lowrise (1-2 story). The city centre is not crazily dense, just pretty uniform 4-8 story buildings (with very few lower than 4s), nor is it big, probably 1/10 of the city itself. 45 minutes on foot from the centre it becomes more like a typical Canadian suburb. The conclusion is that density is actually very easy to achieve - just have consistent midrise buildings with nothing tall and you end up VERY high density without the city feeling overwhelming at all. On other hand, cities with a 10,000 person/sq km look "dense" on paper, but if you really walk around, they are not really that dense at all and most of the place will be lowrise.