This entry is part of our new Research News section, where we’ll write about recent research findings relevant to bike advocacy. Subscribe to the Research News feed here.

Our number one tool for tracking bike commuting is the American Community Survey, or ACS. Conducted annually, the ACS gives us insight into nationwide bike commuting trends. While it is our go-to source for bike commuting data, it also is a lamentably incomplete measure of bike commuting. Because the survey wording only asks about one’s primary mode of transportation to work, the ACS doesn’t count people who combine biking with another, longer mode. It also doesn’t include people who bike commute once or twice a week, or less often. So, even though the ACS puts the 2010 U.S. bike commute share at 0.53%—that’s more than 730,000 Americans (for comparison’s sake, that’s also about 10 times the number of licensed bicycle racers)—we know there are plenty more people out there for whom a bicycle is an important mode of transportation to work. The question is, how many more?

We recently came across a report from the 2003 Omnibus Household Survey that sheds some light on what percentage of workers combine bicycling with a second, longer mode for their commute. The survey found that 7% of all workers usually use a combination of modes to get to work. Of that 7%, 4.2% combine a private vehicle and biking, and 1.2% combine public transit and biking. That means nearly 0.4% of workers (.378%) ride a bike to work most days but combine it with another (almost definitely) longer leg and therefore wouldn’t be counted by the ACS.

This doubles the ACS estimate, which was 0.38% in 2000 and 0.4% in 2005. And we’re still not including people that do bike commute but not often enough to be counted by these surveys.

Why is the portion of multimodal bike commuters just as large as bike-only commuters? Well, the average American commute is long—15 miles one-way, with less than one-third of commutes at five miles or less one-way. Thirty miles (think two hours of riding at 15 mph) is a relatively lengthy distance to bike every day, even for a fit bicyclist. But when you combine that thirty-mile bike ride with transit or even a car trip, it becomes much more doable, especially on a daily basis. It shouldn’t be too surprising that many bike commuters choose to supplement their ride with a second mode. More and more transit agencies have been working to make their buses and trains bike friendly (see page 94 of the Benchmarking Report), which helps too.

Although the percentage difference in the estimate may seen small, the important point is that there are about twice as many frequent bike commuters out there than previously known. If multimodal bike commuting grew at approximately the same rate as the ACS bike commuting, we’re looking at a current frequent bike commuting rate of about 1%. That’s well over 1 million Americans who usually ride a bike to work. When speaking to lawmakers about the importance and legitimacy of bicycling for transportation, this is an important number to have in hand.