Population density is frequently described as people (or housing units) per acre. But I don’t have a good feel for how “people per acre” plays out in a real-life context. What does a street with 15 people per acre look like? One with 30 people per acre? A hundred per acre sounds like a lot — is it a lot?
With that in mind, I recently spent quite a bit of time combining a map of census block-level population data in QGIS with the awesome power of Google Street View to get a sense for what population density feels like at street level. I focused on the U.S. because the data was accessible to me, but I’d love to see similar explorations of living arrangements around the world — especially European and Japanese cities.
My strategy was to pick blocks across the metro area that represented a variety of population densities. This was done in a quasi-random way — I tried to distribute the locations around the metro area, and I haven’t picked particularly nice or ugly blocks. I just looked at a map of population densities, picked a likely block, navigated there in Street View, and snapped a screen shot. The population density numbers I quote are the averages of the two adjacent facing blocks.
A caveat is that I focused on streets that were primarily residential, which will have higher population densities than blocks which contain other uses mixed in. On the other hand, residential uses constitute a large majority of the acreage of any city (e.g. 48% for Berkeley), and the figures I quote do include the square footage of the surrounding streets, which constitute 15-25% of the area of a typical city (24% for Berkeley, from the same source). On net, if you’re interested in bulk population density on a city scale — including shops, schools, offices, parks, etc — you’ll need to deflate these figures by something like 25%.
On to the pictures
1.8 people per acre (Danville):
At the low end, these densities are necessarily imprecise — lot and block sizes aren’t so clear from the air.
12 (Santa Cruz):
15 (Santa Cruz):
18.5 (Santa Cruz):
Both Berkeley and Santa Cruz have a reasonably high fraction of legal or illegal “granny flats” — a separate living unit at the back of the lot. You can see a few in this image.
40 (Santa Cruz):
50 (San Francisco):
Our first townhouse neighborhood is not so high-density: mostly two-story with fairly large backyards
Individual largish apartment buildings can contribute substantial density.
70 (San Francisco):
78 (San Francisco):
Slightly smaller lots.
Fairly large apartment buildings mix with single-family and duplex houses.
125 (San Francisco):
Mostly apartment buildings here.
135 (San Francisco):
Townhouses and apartment buildings. The Bay Area doesn’t get much denser than this.