Atlantic Cities

The Difficulty of Mapping Transit 'Deserts'

The Difficulty of Mapping Transit 'Deserts'
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The Chicago Tribune reports that Chicago is not on pace to meet its goal of doubling transit ridership by 2040. A little early to call things, sure, but the fact is the transit network isn't connecting workers with jobs. The Tribune says that "most jobs in the region can't be reached in a 90-minute commute" (and Brookings recently quantified "most" at a more precise 77 percent). According to a report drafted for a regional transit task force, Chicago suffers from too many "transit deserts":

The Chicago area's mass transit agencies are doing a poor job of serving the commuting needs of the region — portions of which are "transit deserts" — while planning efforts are haphazard, a new report says.

A transit "desert" is a relatively new concept, defined as an urban area full of transit-dependent people (usually city residents who are low-income, elderly, disabled, or all of the above) but lacking sufficient transit service. The report mentioned by the Tribune doesn't identify the exact transit deserts in Chicago, saying only that the term applies to "significant portions" of the metro area. Perhaps the final report, due at the end of the March, will be more precise.

Or perhaps precision here is just too difficult a task. As it happens, a pair of transport scholars recently tried to pinpoint Chicago's deserts — and had a tough time of it.

Using GIS, the duo merged demographic data with transit system data to locate potential deserts in the city (as well as those in Charlotte, Portland, and Cincinnati). The idea was to find specific blocks where high transit demand among dependent riders overlapped with a low supply of transit service. The biggest service gaps they found were in the neighborhoods of Edgewater Beach (well north of the city center), and West Loop and Near North (both downtown).

Here's the transit desert map; the darker the shade, the greater the service gap (via the Journal of Public Transportation):

Thing is — as the researchers themselves admit — Edgewater Beach is known to have pretty decent transit service. The core is well-served, too, for the most part. In an effort to isolate transit deserts down to a block-by-block level, the researchers might have made their measurements too fine. "Thus, certain areas that, in reality, are served well by transit, are shown as bereft of service," they write.

The Tribune, meanwhile, reported some potential transit deserts in the low-income or remote areas where one might expect them. It specifically mentioned several neighborhoods at the far South Side of the city, including Roseland, Pullman, West Pullman and Altgeld Gardens — areas with very high minority populations. It also mentioned western McHenry County, a traditional agricultural center far outside the city center.

Suffice it to say, identifying transit deserts with GIS remains a work in progress. The effort might seem superfluous, given how easily one can point to general gaps in a city's transit network as the Tribune did, but there's a tremendous value in precision here. With transit funding in limited supply, targeted investments become that much more important. It's always going to be hard to serve transit deserts, but determining exactly where they are is a key first step.

Top image: Thomas Barrat/Shutterstocck.com

Eric Jaffe is a contributing writer to The Atlantic Cities and the author of A Curious Madness (2014) and The King's Best Highway (2010). He lives in New York. All posts »

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