In 2013, WSDOT was directed by the Washington State Legislature to raise $200 million from tolls for the SR 99 Tunnel Project. The Advisory Committee on Tolling and Traffic Management studied ways to refine tolling of the SR 99 tunnel to minimize traffic diversion and meet funding goals, and investigate strategies to reduce or mitigate diversion. The committee submitted recommendations in 2014 (pdf 1.8 Mb).
In summer 2016, WSDOT commissioned an independent traffic analysis firm to conduct a traffic and revenue study that will inform the toll rate setting process. Learn more about the study at WSDOT's Tolling page