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):
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.