Thursday, September 15, 2011

Bike-o-nomics: Infrastructure, Part 2

A reader and economist friend e-mailed me in response to my post on bike infrastructure and biking to argue that there is a lot of endogeneity at work with infrastructure as well as politics and socialization.  I agree completely and will discuss each below, but I was trying to focus on a simple point in the post: though many factors are clearly at work, it seems quite likely that part of Portland's exceptionalism is its aggressive push on bike infrastructure.

It is simple economics, reduce the cost of an activity and more of the activity typically happens.  Same thing with increasing the benefits.  Bike infrastructure reduces the cost of biking making it safer (or at least feel safer), reduce car/bike conflicts, decrease travel times, etc.  It may also increase the benefits, for example the Springwater trail which I take to go downtown is a lovely ride and increases the pleasure if the ride (as well as substantially reducing the cost).

But of course it is also true that the more bikes on the road the greater the need for infrastructure and this pressure prompts the city to provide it.  So the causality does not all run one way and I didn't mean to suggest it does.  But the interesting empirical question remains, what explains the fact that Portland has increased ridership so much faster than other cities?

Credit: New York Times

Washington, DC, for example, is a great biking city over-run with young hipsters and in 1990 the proportion of bike commuters is roughly equal. It is realtively flat, the weather is generally conducive to biking, etc.  I lived there in 1993 and enjoyed biking all around.  I would argue that the lack of equal bike infrastructure along with the great subway system makes biking more costly and public transportation less costly relative to Portland.  So while the growth of infrastructure in Portland is partly in response to bikers, the the number of bikers seems to clearly respond to infrastructure investment.

There are also two other feedback loops that were mentioned.  The first is the political one: more bikers means more political pressure that can (and is) brought to bear on local bureaucrats to provide more bike infrastructure. More infrastructure, more bikers, more political pressure, etc.  The second is the social aspect of biking.  The more that do it the safer one feels in doing it as well, the more socially acceptable it is, the more 'doable' it seems and the more fun it is potentially.  However this can also become a cost - bike traffic jams and difficult traffic (e.g. Hawthorne Bridge at 8:30am) can make the commute more burdensome.

The point of the original post is precisely that it is not obvious to me why these feedback loops would be so much stronger in Portland.  They may all be a little stronger, but the increase in bike commuters in Portland over the last decade suggests that this is not a complete explanation.  I suspect then, that it it probably the case that Portland is exceptionalism is due to an above average push for infrastructure.

What I don't know is if my notion of more aggressive bike infrastructure spending in Portland is correct.   The only data I can find in a quick search is from a paper by Jennifer Dill and Theresa Carr of Portland State which includes a table that suggests Oregon was second only to New Mexico in terms of 'average spending per capita for pedestrian and bike infrastructure.' But this is not really informative enough to make the connection to the graph above.

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