I've made a series of graphs and maps on car ownership levels for several US urban areas, as well as comparing car ownership levels to population density (and maybe in subsquent posts, other factors such as income). I looked at New York City first, and then a few others afterwards. The maps aren't the cleanest, but I don't have much background in mapping. Biggest issue I had with the maps is that census tracts boundaries include water, and I'm not sure how to clip them to include only land. While numerous sites that display census data in a friendly way (census explorer, citydata, socialexplorer, etc.) have some maps on cars per household, I don't think any has cars per adult. And rather sure none has car density maps.
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New York City
The map is by census tract, and it's a bit of a mess as census tracts include water. Cars per adult. For the entire region, the stars are MTA commuter rail stops (Metro North / LIRR); I had trouble finding location data for NJ Transit. Interested in seeing if commuter rail access affects car ownership at all, as well as using it as a reference to help figure out what town you're looking at.
Black lines are county boundaries. While the city has a much lower car ownership level than the suburbs, inner suburbs have somewhat less than outer (perhaps more one-car families). The car ownership levels change gradually at the Queens-Nassau border. Further out, the lower car ownership spots are mostly relatively poor and immigrant heavy suburbs. This is ACS survey data, so there's some error; don't read too much into individual census tracts; just the overall pattern. There are some random very low car ownership spots surrounded by much higher adjacent spots; I suspect most are from small sample size issues, rather than anything meaningful. But a few probably aren't; a census tract on Fire Island shows much lower car onwership than its surroundings, reasonable since there's not much of a road system.
Now zoomed in to just the city. Gray line correspond to subway lines, light black borders correspond to community board boundaries. Thick black borders are county lines or borough boundaries. It's fairly obvious from the map that car ownership is far lower near the parts of the city with good subway coverage. While it's likely that better transit reduces car ownership, the neighborhoods covered by subways tend to be older and denser, with cars in general less useful, so it's possible the subway isn't a cause but just correlates with low car ownership.
While the denser parts of the city have a lower rate of car ownership, higher density also could mean a higher concentration of cars. Which effect wins out? The image of a big, dense city neighborhood is often one of lots of traffic and lots of street parked cars despit lower car ownership. Here's a map of car density.
The city in general has a higher car density than the surrounding suburbs. But car density appears to not vary much as much car ownership levels within the city. Many of the higher peaks in relatively dense but somewhat more auto-oriented neighborhoods. Southern Brooklyn has a lower population density than northern Brooklyn but appears to have a similar or higher car density. A few Manhattan spots have very high peaks; it's from a combination of somewhat high car ownership levels (for Manhattan standards) and very high population density. Upper Manhattn has only a slightly lower population density than say the Upper East Side, but much lower car density. Anyone search for street parking in either neighborhood knows that already. Here's a map of population density to compare:
You can see the population density and car density maps have some big differences. Here are car per household maps since some might find them a more meaningful number:
I thought the car density numbers were particularly interesting. Does car ownership levels in NYC go so low that population density no longer increases on car density? Yes. Scatter plot of car density vs population density; each dot is a census tract. You can see car density rises nearly linearly (not quite 1:1) with population density. Past a certain it levels off, and the correlation becomes weak. This over the entire NYC urban area, not just the city.
Now let's how car density corresponds with car ownership levels. Does lower car ownership neighborhoods result in neighborhoods more crowded or less crowded with cars? Some have assumed low car ownership should imply non-crowded streets; others have assumed low car ownership neighborhoods = high density = streets full of cars. As you might have guessed from the map, car density is generally the lowest in high car ownerhship neighborhoods (low density) but at lower car ownerhisp levels, the relationship between car density and ownership is weak. The lower left corner (near zero car ownership and near zero car density) doesn't make much sense; I suspect some of those census tracts have non-residential land skewing the density number.
So, is this just a NYC pattern? Obviously, NYC has far more high density and low car ownership rate areas. But would cities that some similar neighborhoods, say Boston or Philadelphia have similar relations with car density? Any questions on the maps? Do they all make sense?
Linear Mode
