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Purpose & Need

The draft purpose and need statement (pdf 260 kb) is an essential part of the environmental process. It explains why the project is being proposed and why it is a worthwhile investment of time and money. The purpose and need statement also helps provide context and criteria for developing a range of possible alternatives, and eventually the selection of a preferred alternative.

Purpose of the I-90 Tolling Project

The purpose of the I-90 Tolling Project is to manage congestion and traffic flow on I-90 between I-5 and I-405, which is in the Cross-Lake Washington Corridor, and contribute revenues to the sustainable, long-term funding for timely completion of the SR 520 Bridge Replacement and HOV Program and maintenance and future transportation improvements on I-90 in the Cross-Lake Washington Corridor.

Need for the I-90 Tolling Project

The ability to move people and goods needs to be improved and preserved on both I-90 across Lake Washington and in the overall Cross-Lake Washington Corridor, and additional revenues are needed to complete the SR 520 Bridge Replacement and HOV Program and support maintenance and other improvements on I-90 in the Cross-Lake Washington Corridor. The following sections describe current and forecast future conditions in the corridor and demonstrate the need for tolling and congestion management.

  • Manage congestion on I-90 - Current travel conditions on I-90 between I-5 and I-405 are congested, particularly during rush hour. During these periods, traffic conditions in all lanes of I-90 between I-5 and I-405 are characterized by reduced speeds or even stop-and-go traffic. Traffic volumes on I-90 have increased approximately 15,000 vehicles per day following implementation of tolls on the SR 520 floating bridge.

    Long-term forecasts for growth in the region show continued steady increases in population and employment, which means increased use of the region’s highway network and increased congestion even with planned and foreseeable improvements to transit systems and demand management programs. Regional forecasts anticipate the population of King County to increase from approximately 1.93 million in 2010 to 2.56 million in 2040, a 33 percent increase.

    Employment forecasts are estimated to increase by 50 percent from about 1.2 million to about 1.8 million jobs between 2010 and 2040. The largest portion of this growth will occur in Seattle and the east side of Lake Washington, both of which are served by the Cross-Lake Washington Corridor.
  • Raise Revenue for Cross-Lake Washington corridor improvements - The portion of the SR 520 Bridge Replacement and HOV Program between I-5 and the Montlake Interchange is currently underfunded by $1.4 billion. In order for the project to remain on schedule, funding must be secured by the end of 2016. Delays would extend the time users depend on seismically-deficient structures that are at risk of failure or sudden closure due to an earthquake. The loss of the I-5 to Montlake portion of SR 520 would place a tremendous burden on I-90, I-5, I-405, and much of the central Puget Sound region.

    Revenue is also needed to provide a sustainable, long-term funding source for maintenance and potential improvements on I-90 in the Cross-Lake Washington Corridor. For example, additional ramps and HOV/HOT connections at the I-90 and I-405 interchange.