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What tolling the entire Puget Sound would look like

If you want to see what tolls will do, just look at the 520 Bridge experiment. (WSDOT Photo)

The state is considering tolls on I-90 to help pay for the 520 Bridge project. The tunnel through downtown Seattle is going to be tolled. The Washington State Department of Transportation is also looking at requiring three people to use the HOV lane on I-405.

If you want to see what tolls will do, just look at the 520 Bridge experiment. A year into tolling, trips across the bridge are down 30 percent. That’s 30,000 fewer trips on 520 each day.

More than 10 percent of those trips went to I-90. Some went to Highway 522. Others have gone into transit or vanpools.

Ted Trepanier is a traffic analyst with Kirkland traffic management firm Inrix. He also spent 26 years with the Department of Transportation. Trepanier said adding tolls on certain corridors simply moves traffic around, reducing congestion in one spot and adding it in another: system-wide. Drivers have no where to go. So they’ll look to get out of their cars.

“If you go system-wide with those kind of shifts, opposed to one corridor, that means your overall congestion levels will go down,” he said.

He said it’s too soon to say whether the state will eventually have to toll I-5 to help manage the congestion caused by the toll on the new Alaskan Way tunnel.

But he says it’s a possibility.

About the Author

Chris Sullivan

Chris Sullivan is a traffic reporter for KIRO Radio 97.3 FM. He cares deeply about the amount of time you spend sitting in Seattle traffic. Email Chris at


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