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City of Seattle
Ed Murray, Mayor

SUBJECT: SDOT and Nelson/Nygaard Answer Downtown Traffic Question

4/22/2011  1:15:00 PM

SDOT and Nelson/Nygaard Answer Downtown Traffic Question 
Ready to brief city council and public on report

SEATTLE – The Seattle Department of Transportation (SDOT) yesterday released the full Nelson/Nygaard report on the impacts of tunnel tolls on Seattle streets. The Nelson/Nygaard tunnel tolling diversion report shows that traffic on downtown streets under a surface and transit scenario in 2015 would be 155,000 vehicles per day. Conversely, traffic downtown due to tolling of a deep bored tunnel would be 158,100 vehicles per day. This provides the complete answer to a question raised by the city council in January 2011.    
The Nelson/Nygaard analysis, using data from the Washington State Department of Transportation, shows that traffic on downtown streets is virtually the same for a surface and transit solution versus a tolled deep bore tunnel. In 2015, the combined traffic on downtown streets from west of I-5 through Alaskan Way is approximately 155,000 vehicles per day for a surface and transit scenario and 158,100 vehicles per day for a tolled deep bored tunnel. This analysis is based on a screenline at Seneca Street for surface Alaskan Way and all streets west of I-5.

“At the time Tim Payne responded to council questions, we did not have full information about the traffic impacts for downtown streets,” said SDOT Director Peter Hahn. “We commissioned the recently released report in part to fully answer the question of traffic levels on city streets.”

Tim Payne, principal with Nelson/Nygaard, said, “the recently released tunnel tolling diversion report allows us to answer the question of how to mitigate the negative effects of vehicles avoiding the tunnel.”
SDOT and Nelson/Nygaard look forward to sharing the report’s findings in full with the Seattle City Council and the public.

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