SR 99 Tolling

SR 99 Tunnel Project

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SR 99 Tunnel Tolling Studies

The Washington State Transportation Commission is responsible for setting toll rates. Learn the basics about how tolls will work for the SR 99 tunnel.

For information on tunnel construction and budget, please visit the Alaskan Way Viaduct Replacement Program webpage.

What studies are being done on tolling the SR 99 tunnel?

WSDOT has commissioned Stantec, an independent traffic analysis firm, to conduct a traffic and revenue study that will inform the toll rate setting process. This study will help predict how much revenue could be raised and how traffic will likely adjust to a variety of potential toll rates. The study will help the Transportation Commission in setting tolls at a rate that minimizes diversion, but still generates necessary revenue for the tunnel. 

What is an investment-grade 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 would 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.   

What is the purpose of the first phase of traffic and revenue study?

This study does NOT set toll rates. Because bonds will be sold to finance the $200 million, and potential bondholders want to know that their investment will be repaid, WSDOT has contracted for an independent, investment-grade analysis of traffic and revenue for the SR 99 tunnel. Stantec conducted the initial analysis, which by design considers a higher level of traffic diversion – not quite a worst-case scenario, but more than will likely occur. This study provides the assurance that even if many drivers choose another route, tolls would still raise the required $200 million.

Does the final toll rate have to come from the scenarios considered in this study?

No, the toll rates being studied are not recommendations, they are a baseline to start the discussion. The results of the study will be provided to the Commission to inform their work, but they will consider other possible toll rates as well.

What did the first phase of the study find?

The traffic and revenue study has not been finalized, but we have some initial results.

Tolls ranging from $1 to $2.50:

  • Raises at least $200 million, as required by state law.

Tolls ranging from $1 to $1.25:

  • Does not raise the revenue required by state law.

Here is an overview of existing daily traffic volumes on SR 99 and Alaskan Way compared to traffic volumes with the two toll rates studied above:

These results show that some traffic would divert from the SR 99 Tunnel and Alaskan Way to local streets and I-5 no matter what toll rates were chosen. More people would be expected to take other routes during off-peak times like middays, evenings, and weekends than during the peak commute. 

Will tolling the tunnel affect traffic patterns on other roads?

The tunnel will change how people choose to get around Seattle no matter what toll rates are chosen. Unlike the current viaduct, the tunnel will only provide a route for vehicles seeking to bypass downtown and will not have downtown on or off ramps. Depending on where you are going, the tunnel may make some trips shorter and other trips longer. Some people who currently take the viaduct downtown may choose not to take the tunnel regardless of the toll rate.

The new tunnel will be one of several transportation investments to the Seattle waterfront over the next several years. In addition to the tunnel, a new Alaskan Way surface street will be built in the footprint of the viaduct with improved connections to downtown Seattle. This, along with other construction and road projects happening around downtown at the same time, will all have big effects on how people get around Seattle completely separate from toll rates.

How current is the data used for the study?

The new study was commissioned in summer 2016 using the best available data at the time. It takes into account the most recent available economic and population data and projections from the Puget Sound Regional Council.

Why was a new study done?

The forecast model must be updated to reflect more recent traffic and economic conditions. Previous modeling efforts were based on data from 2006 and not as robust as what is needed for actual toll rate setting and bond sales.

 What other studies have been done in the past?

Over the past few years, various SR 99 tunnel toll scenarios have been studied in reports to the Legislature and the viaduct replacement 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. 

Advisory recommendations for tolling the SR 99 tunnel (pdf 1 mb) 

Appendices (pdf 1.7 mb)