Earlier this week, Lynda Laughlin at GGW noted a few key statistics about the District of Columbia, released as part of the Census Bureau’s American Community Survey.   Matt Yglesias honed in on the transportation mode share for DC residents:

When it comes to urban transportation, path dependency issues are everywhere. The more car-dependent people are the more political support there’ll be for car-promoting policies. Conversely, the more there retail and job opportunities are already accessible through non-automotive means, the more realistic it is for new residents to get by without a car, or for a family to get by with only one. And one interesting thing about the District of Columbia is that according to the Census Bureau we’re nearly fifty-fifty in terms of commuting patterns.

I don’t know that I buy Yglesias’ notion that DC is near a tipping point.  Certainly, non-auto transportation allows for density, which allows for more street level retail, which can allow more people to shift their lifestyles, etc.  These linkages are well documented, but the path isn’t linear, nor is it purely a market-based reaction – it requires infrastructure, policies to enable it, etc.

The more interesting discussion was on what this data represents.  This data comes from the American Community Survey, showing the mode of transportation of DC residents only (not workers) for their commute trips only.  This is significant because the focus on DC residents alone doesn’t give a full picture of the overall dynamics of the DC Metropolitan area, and the focus on commuting trips alone doesn’t capture the full use of the transportation system, since most of our trips are not commuting trips.

The latter point touches on Yglesias’ assertion that DC is close to the ‘tipping point.’  Arguably, such a point in an urban area would be when there’s sufficient density, diversity, and design to enable non-auto modes to dominate all of those trip types, not just the commute.

The former point, however, notes the Metropolitan emphasis.  And all of this was basically a roundabout way for me to link to this from The New Republic’s blog, noting the importance of emphasizing metropolitan policy over the loaded ‘urban’ policy terminology.  It’s not just arguing semantics, it’s a reflection of how our cities actually function.

Meshing that together with the commuting discussion, TNR has a great graphic of commuting flows in Chicagoland – which still has a huge and dominant downtown office market, yet still sees a wide network of commuting patterns:

I would love to see a similar image for DC.   Considering the relative size of downtown DC, with transit-oriented employment centers in Alexandria, Arlington, Silver Spring, Bethesda, and others, sprawling agglomerations in Tysons and the Dulles corridor, as well as proximate centers in Baltimore and Annapolis – I’ll bet it would make an interesting graphic.