Eight of the routes that use the Alaskan Way Viaduct
  • UW
  • Eight of the routes that use the Alaskan Way Viaduct
Three University of Washington professors have posted the results of a study that shows tearing down the Alaskan Way Viaduct wouldn't cause the sort of gridlock advocates of a deep-bore tunnel have predicted. Rather than the state's forecast of 10 minute delays across downtown if the viaduct were removed, UW researchers say the average is closer to six minutes—and only for drivers who use the viaduct as a "core component" of their commute. “In the rest of the region, on I-5, there’s no indication that it would increase commute times at all," the UW researchers say.

This report clashes with the rhetoric of tunnel supporters who insist a surface alternative would turn downtown into a parking lot. King County Dow Constantine recently said a surface option "guarantees gridlock.” And Governor Chris Gregoire, flanked by tunnel backers on the Seattle City Council, has said it would create a "stalled city."

The UW professors used different traffic models from the Washington State Department of Transportation, which holds most of its experience building freeways in rural areas and suburbs. The UW researchers "added an urban land-use component that allows people and businesses to adapt over time."

Surface/Transit advocate Cary Moon, director of the People's Waterfront Coalition, says report shows that the state's highway modeling isn't founded in city traffic patterns, drivers are more adaptable than highway builders predict, and that viaduct users are particularly flexible because they have so many alternative routes.

I wrote about the UW study back in March, explaining that professors Hana Sevcikova, Adrian E. Raftery, and Paul A. Waddell studied the effect of viaduct removal on 22 routes through Seattle—14 routes didn't use the viaduct and 8 did. For the first 14, they wrote, "There is no indication that removing the viaduct would increase commute times for these routes." For the routes that did use the viaduct, "There is not strong statistical support for the conclusion that removing the viaduct would lead to any increase in travel times."

“This is a scientific assessment. People could well say that six minutes is a lot, and it’s worth whatever it takes [to avoid it],” says Raftery in a statement. “To some extent it comes down to a value judgment, factoring in the economic and environmental impacts.”