I-90 - Front Street Interchange Justification Study

I-90 Front Street Interchange Justification Report map

Study news

  • WSDOT’s study team has identified several potential solutions and is actively analyzing these options to narrow the selections to a few.


Travel through the I-90/Front Street interchange during peak times can be challenging. Vehicles using the eastbound off-ramp sometimes backup onto I-90. Nearby streets also can experience severe congestion with cars trying to get through the intersections near the interchange or waiting to get onto or off I-90. The Washington State Legislature allocated funding in 2017 for WSDOT to study potential improvements to the I-90/Front Street interchange area in Issaquah. 

Why is WSDOT studying the I-90, Front Street interchange?

Commercial and residential development, as well as the population, in Issaquah and surrounding areas of King County are expected to grow substantially by 2040. This will add more traffic to the I-90/Front Street interchange, a key access point for local residents and commuters. The interchange already experiences severe congestion during peak commute times, which has significant effects on both mainline I-90 as well as Issaquah’s surface streets.

WSDOT is working with local agency partners and other stakeholders to determine the potential causes of congestion, analyze potential alternatives to alleviate it and, if data supports the need for interchange improvement, we will document it in an Interchange Justification Report (IJR). An IJR is a study that analyzes proposed or existing access points to freeways and highways in Washington State. The IJR would be supported by technical studies of local traffic movement and potential future uses of the interchange. The current effort will also consider alternatives, environmental factors, and planning level cost estimates.

Support team

A support team has been formed to provide feedback and direction about potential interchange improvements that address the area’s needs. This support team is made up of representatives from the following agencies:

  • City of Issaquah
  • City of Sammamish
  • City of Bellevue
  • Federal Highway Administration
  • Puget Sound Regional Council
  • King County
  • King County Metro
  • Sound Transit

The end result

If data supports the need for interchange improvements, WSDOT will develop an IJR to help the community and Legislature decide on and plan for improvements to and around the I-90/Front Street interchange.

Needs & benefits

  • Stakeholders: Representatives from local jurisdictions and agencies will provide feedback and direction about potential intersection improvements that reflect the area’s needs and coordinates with the local road projects.  
  • Informs future decisions: WSDOT will provide this study to the legislature as a tool to help it make decisions about the future of the interchange.

What's happening now?

Several potential solutions to address congestion and safety concerns in the I-90/Front Street interchange area were developed based on stakeholder interviews, input from traffic analyses, and input from the IJR support team. These potential solutions were narrowed further by the support team after considering whether the options met the purpose and need on this study and seemed financially and environmentally feasible.

Currently, the project team is performing a thorough analysis of the focused list of potential solutions and will share the results with the support team later this summer to narrow the list of project options further. These selected solutions will then be analyzed, with the goal of identifying one preferred alternative by late 2018 or early 2019.


Late 2017: WSDOT formed a project support team to assist in development of potential future improvements.
Early 2018: Stakeholder input and development of design options.
Mid 2018: Analysis of potential design options.
Late 2018/early 2019: Select preferred alternative.
Mid 2019: Final study delivered to the Legislature.


The Legislature allocated $2.3 million in the 2017-2019 biennium for this study through the 2015 Connecting Washington funding package. 

Funding is currently only available for the initial study. Any future environmental analysis, design, and construction phases will need to be funded through additional legislative action.


Adam Emerson
Project Manager
(206) 440-4279

Dennis Sandstrom
(206) 922-6231