Did NYC Bike Commuting Decrease in 2009? That’s What The Census Says

The Census Bureau released the numbers from the 2009 American Community Survey earlier this week, offering a detailed look at how Americans get to work. As Angie noted on the Streetsblog Network, some unexpected cities like New Orleans and Honolulu jumped up the chart on bike commute rates. Here in New York City, believe it or not, the ACS showed a small decline in the percentage of commuters who bike to work and a drop in the total number of bike commuters.

This marks the second year in a row that the ACS has recorded a decrease in NYC bike commute rates, which doesn't jibe with other measurements of city bike volumes and contradicts the widespread perception that bicycling is increasing. The NYC Department of Transportation screenline count recorded a 26 percent year-over-year increase in cycling in 2009, and Transportation Alternatives put the increase at 28 percent. So what's going on?

The divergence between Census data and those two measures of bicycling is not new, and points to shortcomings in each method. On the one hand, the Census almost certainly underestimates the number of cyclists, by only counting people who bike as their primary mode of getting to work. That leaves out people who only bike a few times a week, or only for errands or recreation. On the other hand, DOT's screenline count measures cycling into the Manhattan CBD, which can distort the picture if cycling rates are much higher in Lower Manhattan and northwest Brooklyn than the rest of the city.

New York won't have a clear and reliable estimate of citywide cycling until more reliable metrics are released. For now, the numbers are the subject of some dispute.

Rutgers professor John Pucher, author of the study "Cycling in New York City: Innovation at the Urban Frontier" [PDF], argued that the ACS data are more reliable as a citywide metric than DOT's count. "I trust professionally trained statisticians who try to create a statistically representative sample as opposed to screenline counts which cannot claim to be representative in any way," he said.

But the ACS findings include a few hard-to-swallow stats that have some questioning the results altogether. "I just don't see that any credence can be given to these numbers," said Charles Komanoff, who developed TA's estimates. He pointed not only to the widespread observation that more bikes than ever are on the street, but to inconsistencies in the borough-level ACS data. For example, the ACS shows the number of bike commuters in Staten Island falling by almost 90 percent. "586 out of Staten Island's previously counted 658 bike commuters would have had to die, retire, get thrown out of work, move or give up cycling," scoffed Komanoff.

Similarly, TA's Noah Budnick argued that DOT's counts seem more accurate. "Just look at the streets," he said. "They're teeming with more bike riders than ever before."

Michelle Ernst, an analyst with the Tri-State Transportation Campaign, also suggested that the borough-level ACS data were suspect, saying that the sample sizes were simply too small to be accurate. She wasn't willing to dismiss the ACS data entirely, however. Instead, she noted its limitations, wondering whether overall cycling trips may be increasing while bike commuting stagnates.

Even if the borough-level numbers are extremely imprecise, however, the divergence they present is striking. While the ACS showed plummeting bike commuting rates in Staten Island and the Bronx, it recorded an increase in Brooklyn. That lends some credence to those who say that DOT's screenline counts capture a western Brooklyn-based upward cycling trend more than a citywide one.

"That screenline count is totally unrepresentative of what's going on in the city as a whole," said Pucher. "It's not impossible that in that area of west Brooklyn and the Lower East Side, that you could still have that 26 percent increase in the screenline counts" even as bike commuting decreased citywide. Pucher said it's telling that the ACS doesn't diverge from Portland's local counts, which he said are more thorough than New York's and include a travel survey.

Pucher said he didn't know why citywide bike commuting might have declined, but that with two consecutive years of ACS data saying so, he's convinced.

To get a better sense of what's happening on the street, many are anxiously awaiting two forthcoming data sets. Ernst highlighted the 2010 Census, which will have a much larger sample size than other studies. "We'll get much more detailed data, block-level data," said Michelle Ernst. "Anecdotally, I've seen a lot more people out on their bikes, in the bicycle lanes, and especially a lot more women," she continued. "Maybe this is happening on a very local level."

Pucher said that he's excited to see the results of this year's National Household Travel Survey. The release of that information has been delayed to make some technical revisions, he said, but once released it will help paint a much fuller picture of American travel habits. "It's a fairly large sample and it includes both work trips and non-work trips," he explained.

Until the new data is released, we have two imperfect and contradictory sets of information -- and our own observations. Let us know what you've seen on the streets of New York. Is cycling up across the city or just in certain parts? Bronx and Staten Island readers, especially, does the Census data match what you're seeing on the street?