Saturday, September 18, 2004 - Page updated at 12:00 AM

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Traffic "gridlock" if viaduct torn down, study says

Seattle Times staff reporter

If the Alaskan Way Viaduct were torn down and not replaced, traffic along Alaskan Way would more than quadruple and the number of cars on downtown streets would grow as much as 50 percent, according to a new study released yesterday by the state Department of Transportation.

While the state initially said it wouldn't study the option of not replacing the viaduct because it believed viaduct traffic must be maintained, it agreed to the study after a group of environmentalists and others asserted building a replacement would be too expensive and disruptive. Some members of the Seattle City Council also asked that a no-replacement alternative be added to the five under consideration.

The People's Waterfront Coalition, a group of planners and environmentalists, in April slammed the environmental-impact statement written for viaduct replacements and said the viaduct should be torn down.

It proposed a sixth alternative, a package of smaller projects to keep traffic moving through downtown without the viaduct. Those projects include reconfiguring Interstate 5, improving downtown arterials and signal timing, expanding transit and adopting tolls and other strategies to discourage driving.

Cary Moon, co-founder of the waterfront coalition, said she expected the state report would dismiss the no-replacement option.

But, in a letter to the state Department of Transportation (DOT), Moon said the state needs to look at encouraging people to avoid nonessential trips, should look at specific projects to improve traffic flow on I-5, and should identify improvements to bus service that would take cars off the viaduct.

"The data on which the decision is being judged is primarily about road capacity, travel times and capital project costs," she said. "These measures capture only a small part of the true cost/benefit picture."

The DOT, in its new report, said tearing down the viaduct and not replacing it would create gridlock on I-5 and downtown streets.

It predicted Alaskan Way along the central waterfront would get more than five times its current traffic volume. As many as 56,000 cars would use Alaskan Way, compared with 10,000 today. And traffic on already pressed I-5 would increase by as many as 33,000 vehicles a day.

Downtown street traffic would increase 30 to 50 percent, with the greatest increase in Pioneer Square and along the waterfront. I-5 has no more capacity, and adding capacity to the freeway would cost billions of dollars.

The state found neighborhoods, particularly Ballard, Queen Anne, Magnolia and West Seattle, also would be affected if there were no viaduct.

The state study assumed a four-lane surface street along Alaskan Way, with a single lane in each direction connecting it to the Battery Street Tunnel. It also looked at improved transit and at operational changes to I-5.

"Even with the most optimistic assumptions ... the four-lane surface option would result in gridlock on I-5 and congestion for most of the day and into the evening on downtown streets and Alaskan Way," the state report said.

These are similar findings to those released by the state last week on the option of closing the viaduct during construction of a replacement. It found closing the viaduct while it rebuilds or replaces the structure with a tunnel could save $300 million to $500 million and shorten construction by as much as 2-1/2 years.

But traffic would be a mess.

There are five options for replacing the viaduct, but the state last week said it had essentially narrowed the alternatives to two: a tunnel or reconstruction of the existing structure. The three other options still are on the table, but they are unlikely choices.

The tunnel would take from seven to nine years to build. Rebuilding the viaduct would take six to eight years.

The state said the study confirms that the viaduct cannot be replaced with a four-lane surface street and other transportation improvements. A preferred alternative for replacing the viaduct will be announced sometime during the fall.

Susan Gilmore: 206-464-2054 or

Copyright © 2004 The Seattle Times Company


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