SR 99 Tolling

SR 99 Tunnel Project

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SR 99 Tunnel Toll Rate Study

This page answers in-depth questions about the SR 99 Tunnel toll rate study and links to additional resources.

What is the goal of the study?

We are currently studying how drivers would react to hypothetical toll rates so we can estimate how much revenue could be raised and how traffic patterns would change based on various toll rate options. The goal of this study is to help the Washington State Transportation Commission find toll rates that minimize traffic diversion to other roads but still raise the legally required $200 million to help pay for the Alaskan Way Viaduct Replacement Program.

Will the final toll rates come from this study?

The rates discussed below are not recommendations; they are a baseline to start the discussion. The Transportation Commission is in the process of considering what other options should be studied.

What do the initial results tell us about revenue?

The traffic and revenue study has not been finalized, but initial results provided to the Commission showed:

  • Tolls ranging from $1.00 to $1.25 throughout the day do not raise the $200 million required by state law.
  • Tolls ranging from $1.00 to $2.50 throughout the day raise at least the $200 million required by state law

What does the study tell us about traffic?

The tunnel will change how people get around Seattle for many reasons besides tolling. The initial analysis considers the combined changes to downtown Seattle traffic from the tunnel and other local construction projects, while future results will look more directly at the effect of tolling on its own. These maps show how traffic is predicted to shift at specific locations as a result of all these factors:

What is a traffic and revenue study?

This type of study predicts drivers' willingness to pay various toll rates so we can forecast how much revenue could be raised and how traffic patterns could change based on various toll rate options. This study is needed to support both the rate setting process and the sale of bonds to finance the $200 million capital investment required by state law.  

This study was intentionally designed to be conservative. This may result in higher estimated traffic diversion and lower estimated revenue is likely to occur. This is important because it helps make sure that we are carefully planning for changing traffic patterns and so that potential bondholders can be confident that tolls will raise enough to repay their investment.

Why are study results referred to as “preliminary”?

The results we have released so far are a robust analysis of a few hypothetical toll rates. The study will not be finalized until toll rates have been set by the Washington State Transportation Commission.

What other information have you released about the SR 99 Tunnel Tolling study?

The best place to start learning about how SR 99 tunnel tolls will affect traffic and revenue is to read this summary of the most recent study results.

The Washington State Transportation Commission (WSTC) is leading the toll rate-setting process. In-depth updates about this study and their process can be viewed on the WSTC website:

What other studies have been done in the past?

During the past few years, various SR 99 tunnel toll scenarios have been studied in reports to the Legislature and in the Alaskan Way Viaduct Replacement Program’s environmental documents.

WSDOT and the City of Seattle established the 15-member Advisory Committee on Tolling and Traffic Management in fall 2011. In 2014, the committee made advisory recommendations on strategies for tolling the SR 99 tunnel to raise revenue while minimizing and mitigating traffic diversion onto city streets and I-5. These recommendations were shared with the Governor, Legislature, State Transportation Commission, WSDOT, Seattle Mayor and the Seattle City Council.