Census Bureau: Portland bike commute mode split doubles in five years

Posted by on January 12th, 2007 at 12:30 pm

PDOT has just sent me results from the U.S. Census Bureau’s American Community Survey.

According to the numbers, Portland’s bike commute mode split has grown 96% from 2000 to 2005, nearly doubling from 1.79% to 3.51% (mode split is just a wonky way to refer to the % of usage of various transportation modes).

Check out the trend in the graph below (click image for larger view):

Bike commute mode share in Portland 1990-2005. Source: U.S. Census Bureau

Behind the numbers

I asked Jessica Roberts (formerly with the BTA, now at Alta Planning) for the inside dope on these numbers.

She said it’s important to remember that this survey is only concerned with trips to work (which account for a mere 1 out of 8 bicycle trips). She added that it’s widely accepted by planners that these numbers vastly under represent mode splits. At the same time, Jessica says the data is very helpful as a comparative tool because it has been kept for so many years and the methodology has remained consistent.

Jessica also told me how the Census Bureau conducts the survey. She said each year in April (which is quite rainy in Portland) the Bureau calls a sample of people and asks the following question,

“In the last week, what was your primary means of getting to work?”

The respondent is only allowed to give one answer. So, if they drove a car 3 days of the week and biked or took transit 2 days, their answer would have to be driving their car.

As for arriving at a mode split number for bicycle use overall in the City, Jessica said that number is the “Holy Grail” of planners and advocates and remains elusive.

Numbers aside, the important thing is that according to this survey we’ve doubled our bike to work trips in the last five years. That is a great trend that bodes very well for the future.

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Hawthorne RiderScott MizeeJeffFritzAttornatus_Oregonensis Recent comment authors
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sweet! But it seems that leaves a lot of room for fuzziness. One question:

when they survey by phone do they just call landlines or are they allowed to call mobiles? Do they just call homeowners or renters too? It seems these factors could make the age demographic vary a lot…

But it least it’s cool that the methods have been consistant, so even if they’re way off, they’ve still doubled!


Before I was an attorney, I was a psychologist and so I have some training in survey research. I can tell you that the survey would be designed to be representative of many demographic factors, such as homeowners v. renters. However, by law people conducting surveys are not permitted to call cell phones and I think there is ample reason to believe that this would cause an under representation of bike commuters. I am one of the many younger folks who have no landline. Nevertheless, as mentioned, the fact that the data show great increases at least makes clear that bicycling is rapidly increasing as a mode of transportation.

On a slightly different matter, my view is that a phone survey is a really poor way to do an estimate of something when that phenomenon can be directly observed. Why don’t they just go out and count the number of people on busses, in cars, and coming across the bridges on bikes (I know they do the last one)?

And, as an aside, next time you’re riding the bus or standing on the street corner, look at the cars that go by. Count the number with one person v. those with more than one. It’s not even close.


“As for arriving at a mode split number for bicycle use overall in the City, Jessica said that number is the “Holy Grail” of planners and advocates and remains elusive.”

My question is:
What can WE, the cycling community and BikePortland visitors, do to help get this number nailed down?

A Poll Forum?

A BikePortland Polling Team?


I would say we should ask the folks at BTA whether they feel there is a need for better data in order to provide support for their advocacy arguments generally. If they feel so, they may be willing to commission a study. A fair portion of the budget of such surveys is the data collection labor, so if they had volunteers willing to be trained, it may help…

But BTA say that there isn’t enough of a need to spend their precious funds on estimating what most folks already accept, that the rate of cycling is increasing by leaps and bounds.

Personally, I think it’s being underestimated by current techniques, so a more accurate would provide a stronger argument, possibly much stronger, depending on how greatly our numbers are being underestimated.


3½isn’t anything to sneeze at. I’m looking at thenumbers for some other cities and I’m seeing good increases elsewhere.


I believe it’s a mail survey, thus avoiding some of the random sampling problems inherent in the rise of cell phone use. If you don’t fill out the form in a timely manner, the Census Bureau thugs come a-knockin’…

Scott Mizee

[quote] Fritz
January 12th, 2007 15:50 53½isn’t anything to sneeze at. I’m looking at thenumbers for some other cities and I’m seeing good increases elsewhere.

What were some of the percentages of the other cities?

Hawthorne Rider
Hawthorne Rider

Yes, it is a mail survey. My household was randomly selected a month or so ago to take it (and, as Jeff notes, they were very insistent I did it – I received a 2nd survey in the mail reminding me to do it!). I proudly put bike as my main transport to work! Perhaps, they do phone surveys to follow up on those households that don’t complete the mail-in version?