Still the one (outlier)

Transit

Still the one (outlier)

by David Alpert • September 29, 2008 10:39 am

Austin Contrarian extended the analysis of the chart of transit usage and density I posted before I left. He noticed the same weaknesses in the data that several commenters did—the absence of some cities, and the arbitrariness of using city boundaries which are small in some cities (like DC) and large in others (like Houston).

AC solved the problem by computing his own metrics. Better than standard density (under which LA is denser than NYC, enabling anti-urbanists like Randal O'Toole distort facts to make points), he used the better weighted density. That correlates very strongly with transit ridership.

Image from Austin Contrarian.

The best correlation of all, though, was in the ratio between standard density and weighted density—the "the degree of clumpiness" of the population.

In all three graphs, one thing stands out: Washington, DC is still an outlier with higher transit ridership than other cities of similar density (standard, weighted, or ratio).

Thanks to Dan Miller for pointing this out while I was away.

8 comments

Tags: density, graphs, transit

The outlier (Sep 17, 2008)
Scatterplot of density vs. transit ridership (Sep 18, 2008)
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GOOD visualization of world transit systems (Feb 21, 2009)
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David Alpert is the Founder and Editor-in-Chief of Greater Greater Washington and Greater Greater Education. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He loves the area which is, in many ways, greater than those others, and wants to see it become even greater.

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DC also has carpeted trains and (thanks to our neofascist food and drink ban) a clean rail system with a modestly small rat population.

I wonder how we rank internationally? London has an old stinky tube like Boston's T. Montreal has a more modern train system like DC's. I would love to see Mexico City on this graph, although "public" transit would have to include the informal minibuses.

by Ward 1 Guy on Sep 29, 2008 10:58 am • link • report

if you build it they will come...

by Cavan on Sep 29, 2008 1:13 pm • link • report

If I were in the Mayor's or City Council's office, looking for ways to increase tax revenue, I'd be very heartened by this result. As I see it, it means we can still boost weighted density almost two-fold -- that is, steal development from the exurbs and move it to inside the District -- by leveraging how much better our transit system is than what the average American has become accustomed to in other cities.

by tom veil on Sep 29, 2008 2:27 pm • link • report

One thing I noted in Austin Contrarian's analysis is that s/he's only including public transport and walking, not bicycles. I don't think it would throw the numbers hugely askew, but I'd still like to see that reflected. WABA should be up in arms.

But weighted density is just LOVELY. Wouldn't it be great if a weighted density analysis were used in evaluating new projects? I suppose that'd really only work if metropolitan planning were coordinated in some way. But I can dream can't I?

by RyanA on Sep 29, 2008 2:30 pm • link • report

What's also interesting about DC is if you look at walk/bike/transit commute share close to transit vs. the region as a whole. DC is also outperforming other systems of similar size (as measured by fixed-guideway stations) graphic here

This is from the 2000 Census, too, before the most recent wave of development around Metro stations really took hold.

by SamZ on Sep 29, 2008 9:35 pm • link • report

Now to figure out some infographic that manages to simultaneously compare system size, weighted density, percentage of commuters, ridership, and years of TOD since service began.

Damn I wish I owned Edward Tufte's series. Or a cage full of Wired Magazine intern-savants.

by Squalish on Sep 30, 2008 6:02 am • link • report

Sq: I think if you changed the dot size to reflect average ridership, and the color to reflect average system age on a blue to red scale, you might have it. Remove the axes and the grid lines, leaving only the axis labels, the slope line and the data.

by Michael P on Sep 30, 2008 6:19 am • link • report

you will actually get a better fit if you introduce a dummy variable to create two curved lines. the tier below the line are cities that all experienced substantial growth during the mid-20th century (LA, San Diego, San Jose) and those above are cities that mostly had their substantial periods of city building in the 19th and early 20th centuries.

by mfs on Sep 30, 2008 10:40 am • link • report