This was originally posted at Noon today.

Because he thinks like this:

"Why hasn’t the city made the proper investments on Linden Avenue as density has increased?  How can we ensure that this doesn’t happen in other neighborhoods?  How much will these investments cost?  If we can’t figure out how to make these investments pencil out, we need to rethink our whole model of sustainability."

Affordable senior housing at Seattle Housing Authority's Bitter Lake Manor

Last week Seattle City Council member Mike O'Brien and other officials visited the Broadview-Bitter Lake-Haller Lake neighborhood in North Seattle, one of only two Seattle neighborhoods that will be getting a neighborhood plan update in 2010 (the other is Rainier Beach).

O'Brien, writing on his blog, was reacting to the pathetic state of the pedestrian environment in a neighborhood that in recent years has seen a major influx of multifamily housing, much of which is for senior citizens and low-income households.

Accommodating density is right in line with the city's goal of directing development to urban villages, creating vibrant, walkable communities. But—surprise!—that formula breaks down when it's inconvenient and/or unsafe to walk, which is even more true for the elderly. For years, the city has failed to address a deficiency in basic pedestrian infrastructure in the area.

Linden Ave N, existing conditions (photo via Bitter Lake UrbanVillagers Voice)

Fortunately, the Seattle Department of Transportation does have plans in the works to upgrade Linden Ave N between 128th and 145th, as well as  N 130th St between Linden and Greenwood. One proposed street section on Linden is shown below.

Proposed street section for part of Linden Ave N (click image to enlarge)

This is a good start. But it's hard to overstate how minimal the investments are in comparison to the need: Given that it costs between $40,000 and $300,000 to build a block of sidewalk—the actual amount depends on how much work is required—addressing the shortfall will necessitate a major reprogramming of transportation dollars.

The bigger issue that O'Brien is stirring up is that since density doesn't work well without adequate public investment in infrastructure and amenities, people who advocate for density as a way of promoting sustainability have an obligation to figure out how to ensure that sufficient public investment happens.

In a world of ever-shrinking municipal budgets, funding infrastructure improvements is even more of a challenge. And relying on the "developers will pay their own way" model—as Seattle has been inclined to do—just ain't gonna cut it. All ranges of incomes should have access to the kind of infrastructure and amenities that make dense urban living attractive.

The burden of demanding meaningful public investment to support urban densification falls on all of us, not just the density advocates. Transforming our urban areas from resource-inefficient, car-dependent sprawl to walkable, transit-rich, compact communities is, I would argue, the most promising strategy for creating more prosperous cities nationwide, and for ameliorating the the pain we're inflicting on the planet as a whole.  If someone has a better idea, I'm listening.

And at the root of the problem is a deadly two-pronger: First, we don't pay enough taxes, and second, our public spending priorities on transportation and the built environment are whacked. Fixing those two things is what it's really all about. O'Brien gets that that's what we elected him for.