The Most Persuasive Evidence Yet that Bike-Share Serves as Public Transit

It substitutes for short trips in the core, and expands service on the outskirts.

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Shinya Suzuki/Flickr

Over the past few days, several New York media outlets have reported that Citi Bike, the city's popular but financially struggling bike-share system, will soon get a much-needed influx of cash. The new money would likely go toward improving docking stations and expanding the network to other parts of the city. A spokesman for Mayor Bill de Blasio told the Wall Street Journal that bike-share "has become part of our public transportation system, and there is a lot riding on its success."

Those words come at the same time as a new research study—first referenced here by former D.C. and Chicago transportation chief Gabe Klein—offers the most persuasive evidence yet that bike-share serves as a genuine form of public transportation.

Past work has found that bike-share members decrease their car use considerably: According to one survey, 52 percent did so in Minneapolis, and 41 percent in Washington, D.C. The new, more fine-grained analysis of bike-share use in these cities reveals that its role in the transit system varies based on the character of the host city. In larger cities with dense cores like D.C., bike-share may replace shorter transit trips; in smaller, more dispersed cities like Minneapolis, it may expand the entire public transport network.

Berkeley researchers Elliot Martin and Susan Shaheen report the findings in an upcoming issue of the Journal of Transport Geography:

The denser the urban environment (particularly for rail), the more bikesharing provides new connections that substitute for existing ones. The less dense the environment, the more bikesharing establishes new connections to the existing public transit system.

That's the take-home message. For the study itself, Martin and Shaheen took a close geographic look at the changes in commute modes made by bike-share members in the two test cities. In Washington, a survey of more than 4,800 members found that 47 percent decreased their rail use (namely, on the D.C. Metro), primarily in the city center. This suggests that in a city like D.C., bike-share acts as a substitute for short rail trips—no doubt relieving crowded subway cars in the process.

Martin and Shaheen found a similar trend with D.C. bus use, with 39 percent of Capital Bikeshare members decreasing their rides, according to the study. Again, most of the that decrease occurred in the urban core, where one can imagine bike-share trips being quicker than short bus rides.

The evidence painted a slightly different picture in Minneapolis, home to the Nice Ride bike-share system. There, 14 percent of Nice Ride members increased rail use, with only 2 percent decreasing it (in a survey of 900 people). Most of those who increased rail use did so along the main commuter corridor, both near the downtown area and toward the outskirts. That makes sense in a midsized metro area like Minneapolis, where the rail network facilitates longer trips into and out of the core. Bike-share can facilitate the first and last mile of these trips, but can't compete with the entire journey.

A comparable share of bike-share members—again, roughly 14 percent—increased their bus use in Minneapolis. At the same time, 18 percent also decreased bus use, with much of the drop occurring in the core. Bike-share may serve as a better alternative to short bus trips in downtown Minneapolis, just as it does for short subway trips in downtown D.C.

Overall, the maps suggest that bike-share, at least in Minneapolis and Washington, is making the entire multimodal transit network more efficient. For short trips in dense settings, bike-share just makes more sense than waiting for the subway—it's "substitutive of public transit," in the words of Martin and Shaheen. For longer trips from the outskirts, bike-share access might act as a nudge out of a car—it's "complementary to public transit." The authors conclude:

In all cases, as demonstrated by its remarkable ability to attract modal share in North America, public bikesharing appears to be improving urban mobility and lowering dependency on automobile travel.

Basic research like this is important in its own right, but it's especially intriguing at the moment because it lays the foundation for bike-share systems to receive public money. Right now, part of the appeal of bike-share for most cities is that it operates using private funding. But with the flaws in that financial model becoming clearer every day, and with increasing evidence that bike-share can expand or support public transit networks, the case for improving these systems with taxpayer dollars becomes much stronger.

New York City wasn't part of this study, of course, and it might not be headed in the direction of public bike-share ownership just yet. But the recent reference to bike-share by the De Blasio administration as "part of our public transportation system" certainly leaves that window open. Time might even look back on these words as the first in a series of comments that ultimately led to the city integrating bike-share into its official transit network.

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