Regular riders of Capital Bikeshare have cut down on their use of rail and bus transit, a new study shows. This is particularly strong for those in neighborhoods a short bike ride from downtown DC.

CaBi’s effect on Metrorail ridership. Images from the study. Click to see the full image.

In these maps, each circle represents one zip code in which researchers Elliot Martin and Susan Shaheen surveyed CaBi users. The number shows how many responses they got in that zip code. Red is the percentage of those people who used that mode of transit less (rail for the map above, bus below). Green is for those who used it more, while yellow is those who didn’t change.

CaBi’s effect on Metrobus ridership. Images from the study. Click to see the full image.

It’s not only transit which riders are using less. CaBi users also have cut down on car trips and probably even replaced some walk trips with bikeshare.

This isn’t necessarily bad for transit. The places where this effect are strongest also happen to be the places where transit is most congested. On the busy Metro lines at rush hour, the trains are full into downtown DC; it’s just as well if fewer people are hopping onto an already-packed train at, say, Foggy Bottom.

And many of the people who ride Bikeshare still use transit some of the time. They might still ride it in bad weather, but at other times avoid it at its most congested, or at times of poor service, like the very long waits on weekends during track work.

One potential danger, though, is that if there is lower demand for service on weekends (thanks to a bicycle alternative), that could make it less likely local jurisdictions want to pay for more frequent transit service at off times, even though not everyone can substitute a bikeshare trip for a transit trip.

Meanwhile, in Minneapolis (which has much less rail transit), the study found that many people increased their usage of rail, perhaps because the bikeshare system helps them access transit much more easily.

Eric Jaffe writes in Citylab,

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.”

Honestly, once I started bicycling (first with Capital Bikeshare, and then more and more with my own bike) I personally cut down significantly on using transit. But I live in a downtown-adjacent area where it’s a fast bike ride to many destinations; for others, that’s not the case, and transit is best for their trips. I also still ride transit some of the time.

Some people in the survey also increased their use of transit. The more transportation options people have, the more they can choose the one that best matches their needs. The road network is already quite comprehensive (though often crowded). We need to offer everyone high-quality transit and bicycling as alternatives so that they can use each when it’s the best choice at that time.

David Alpert is Founder and President of Greater Greater Washington and Executive Director of DC Surface Transit. 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 lives with his wife and two children in Dupont Circle. Unless otherwise noted, opinions here are his and not the official views of GGWash or DCST.