Replacing the viaduct with the surface-and-transit option could stall traffic downtown and encourage highway construction elsewhere.

The current mayoral race has placed the viaduct-replacement issue squarely back into the public limelight after most of us thought the issue had been put to bed, what with the governor’s and Legislature’s approval of the deep-bore tunnel option, as well as the accompanying funding commitments.

Both mayoral candidates have raised the issue of the viaduct replacement, with one issuing renewed and strident calls to reconsider the surface-and-transit option.

While the surface-and-transit option seems to be readily embraced by the nominally environmentally conscious activists, I’ve been wondering recently if their concerns may not be both overly simplistic and somewhat shortsighted, as well as possibly self-defeating.

We have heard and read much discussion in the media about the relative validity of arguments on both sides of the issue of whether the throughput of the existing Alaskan Way Viaduct can reasonably be reduced and/or otherwise accommodated by surface streets.  Activists promote the notion that greater and more attractive transit options will remove a certain amount of the vehicle traffic, leaving the remainder to be accommodated by an enhanced network of the existing surface streets.  Detractors protest that most of the throughput traffic is not transit-compatible and that diverting a huge volume of additional traffic onto the surface streets will create gridlock all day long on virtually all downtown Seattle streets.  These issues have been volleyed back and forth in the public debate ad nauseam, but there’s one additional concern that I have been discussing lately that I have not yet seen much coverage on.

Sharing the concern that simply cutting off one of our region’s major north-south highways will reduce downtown Seattle’s streets to a virtual standstill during most daylight hours, I wonder what impact the sharply exacerbated choke point of downtown Seattle within the Puget Sound area’s north-south regional transportation corridor would have on the pressure to consider future road-building in suburbia and exurbia?

You may remember that every few years pro-development forces on the Eastside raise the issue of the “Foothills Freeway,” or I-605, that would consist of a more distant loop around the easternmost edge of our metropolitan area.  If north-south circulation through the metro area is even further complicated by the removal of one of the region’s vital north-south highways, the I-605 promoters would essentially be offered more fuel for their fire.  Constant gridlock on I-5 and the downtown Seattle streets, coupled with the congestion already on I-405, could lead to a ready-made argument in favor of efforts to pursue an I-605.

And we need to ask: Even if some magical combination of street improvements and synchronized traffic signals could accommodate the existing Highway 99 flow through downtown (which I do not believe is possible), what about future growth?  Do the streets-and-transit promoters think the region will stop growing?

Now, in addition to the already oft-mentioned litany of environmental impacts from potentially gridlocked downtown Seattle streets (i.e., substantially increased vehicle idling and resulting air pollution, increased noise, and a markedly diminished pedestrian environment), we could add the potential consequence that the loss of the Highway 99 corridor through downtown Seattle could lead to the development of I-605.  Any environmentally conscious individual knows that the construction of a major new freeway in any metropolitan area literally paves the way to urbanization in its path.  Is that what we want virtually on the slopes of the Cascades?

Mayor Nickels, Gov. Gregoire and the state Legislature all recognized, and thankfully so, that the viaduct should not be replaced with a new modern-age monstrosity along our waterfront.  They also recognized that the vital transportation corridor that Highway 99 plays not only in Seattle, but in our entire region,  must be preserved.  The tunnel was and is the only option that accomplishes both noble objectives.  Environmental activists need to look beyond their Seattle-centric view of the world and see that Highway 99 is not just a Seattle problem, but a regionwide problem.  And the potential, long-term environmental impacts of the streets-and-transit option are far greater than the theoretical, short-term reduction of vehicle trips that that option is purported to create.