Mercer Island Transit Interchange

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The Mercer Island Transit Interchange is the integration of bus transit service from the Eastside with East Link light rail. When East Link opens for service in 2023, some bus routes from the Eastside to Seattle will terminate at Mercer Island Station, where passengers will transfer to/from light rail.

Learn more by reading the articles below, as well as the FAQs and studying the Document Library; use the tools below to Ask a Question or Post a Comment. [Note: FAQ's were last updated Oct 2020]

The Mercer Island Transit Interchange is the integration of bus transit service from the Eastside with East Link light rail. When East Link opens for service in 2023, some bus routes from the Eastside to Seattle will terminate at Mercer Island Station, where passengers will transfer to/from light rail.

Learn more by reading the articles below, as well as the FAQs and studying the Document Library; use the tools below to Ask a Question or Post a Comment. [Note: FAQ's were last updated Oct 2020]

  • Questions About Transit Interchange Safety

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    16 Jul 2019
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    Do you have questions about how commuter buses will integrate safely with the future light rail service on Mercer Island (opening 2023)? The City Council will be discussing this topic at its July 16 Regular Meeting, but in the meantime we have also crafted a Q&A hitting some of the hot topics the community is discussing right now. The Transit Interchange Safety FAQ (from July 11) can be accessed from our Document Library.

    Park & Ride


  • Planning for the Transit Interchange

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    17 Jun 2019
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    East Link light rail is currently under construction with service set to begin in 2023. One of the remaining issues under discussion regarding light rail on Mercer Island is the integration of the new rail service with existing bus transit at the Mercer Island Station. Sound Transit and King County Metro are seeking to minimize overlap between light rail and bus service along I-90, maximize transit efficiency and reduce air pollution.

    A 2017 Settlement Agreement between the City of Mercer Island and Sound Transit sought to balance the goals of the transit agencies with the City’s desire to protect quality of life for Island residents. The Settlement Agreement outlined the location and design of the Transit Interchange, identifying a roundabout at North Mercer Way and 77th Ave SE as the location for bus loading/unloading and turnaround.

    King County Metro was not a party to the Settlement Agreement, but it was known when the agreement was signed that Metro would need to be involved in planning and implementation of the transit interchange. Thus, after the Settlement Agreement was signed, Sound Transit commissioned the Mercer Island Transit Interchange Operational and Configuration Study (Full Study; Exec Summary) to evaluate how Metro buses will integrate with the light rail station. Since the study was completed, Sound Transit and Metro have been working to further refine plans for the interchange, including the design of the improvements to the right of way, the roundabout, bus queueing and layover areas, and pedestrian, bicycle and vehicle circulation.

    Throughout early 2019, the City Council has also been in discussion with the transit agencies about expected bus operations and the design details of the proposed interchange. The City Council held two Study Sessions (19 March and 30 April, 2019) at which Sound Transit and Metro presented updates on roundabout design and proposed future bus operations. Meeting materials, FAQ, and comments/questions are provided in the articles below.

  • Council Holds Second Study Session on April 30, 2019

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    11 Jun 2019
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    On Tuesday April 30, The City Council held a second Study Session to understand additional details of the proposed interchange and bus operations design. Following this meeting, Sound Transit and King County Metro provided the City with a proposed construction timeline, as well as extensive answers to Council questions (both documents are available in the Document Library). You can watch the meeting footage here on the Council You Tube Channel.
  • Questions Answered

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    26 Apr 2019

    Following the March 19, 2019 Study Session with Sound Transit and King County Metro staff, Council requested additional information and analysis of Sound Transit’s Mercer Island Transit Interchange Operational and Configuration Study (Study). KPG, the City’s on-call traffic engineering firm, will provide a review of the Study and recommendations for station access improvements including Pedestrian and Bicycle Improvements and Signal Phasing Improvements for Pedestrians at a City Council Study Session on April 30, 2019 at 6:00pm at Mercer Island City Hall.

    Responses to the list of Council questions from the March 19 Study Session along with an extensive FAQ are now available.

  • We're Working on Answering All Your Questions

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    22 Mar 2019
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    At the March 19 Council Meeting, representatives from Metro and Sound Transit provided a lot of insight into bus operations and roundabout construction. We received a number of questions during that night's 90-minute session, as well as others that continue to come in via this site. We are gathering data from the agencies and posting the responses as soon as possible...

    You can watch the meeting footage here on the Council YouTube Channel -- Thank you!

  • Submit Your Questions Today About Interchange Operations

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    14 Mar 2019

    In advance of a March 19 Council Study Session (meeting materials posted here), the City is gathering questions from the public about the future operations of the transit interchange that will allow regional buses to exchange passengers with East Link Light Rail trains (starting in 2023). Please use the Ask a Question Tab to submit yours, or check the FAQ page.

  • Background on the 2017 Sound Transit-Mercer Island Settlement Agreement

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    17 Jun 2019
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    In fall of 2017, the City of Mercer Island and Sound Transit approved a Settlement Agreement intended to offset the impacts of light rail construction and operation, and also to partially compensate for permanent impacts to local traffic patterns. The Settlement Agreement includes a package of mitigation measures valued at just over $10 million, including key community-identified priorities:


    • Traffic/Safety Enhancements and Last Mile Solutions: $5.3 million to address vehicle, bicycle and pedestrian access issues resulting from the closure of the Center Roadway and fund “last/first-mile solutions” that enable Islanders to access transit without driving.
    • Parking: $4.6 million that will provide approximately 100 additional commuter parking stalls during the East Link construction period (2017-2023), and will fund construction of new commuter parking for residents.
    • Bus-Rail Integration: No bus facility will be built on 80th Avenue - instead, all pick-up and drop-offs will continue to occur on North Mercer Way and bus volumes will be comparable to today.


    The Settlement Agreement further details the following points of agreement for the transit interchange:

    • A roundabout at N Mercer Way & 77th Ave, and no substantial bus operations/layovers along 80th Ave
    • Future bus volumes less than existing bus volumes
    • No routing of regional buses through MI Town Center
    • Limited occurrences of long bus layovers
    • No bus idling