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]


Do you have a question? Please see the FAQ page for more information. If you have additional questions that you would like addressed, please submit here [NOTE: Questions do not appear publicly until answered]



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    Hello, we were wondering what the city's plans were to increase sidewalks and traffic lights? I appreciate the tip to walk facing and as far away from traffic as possible, but it's nearly impossible to see pedestrians in the dark unless they wear reflective clothing. I would love to see sidewalks and street lights on all the major arterials. There is so much city property on the edges of the streets (we know this because of building codes) that are currently gobbled up by random executions of resident parking, lawns that don't allow street parking at all or rocks placed in those areas so people won't park.

    heatherring74 asked 4 days ago

    We believe you may be referring to an article in a recent City E-Newsletter, not directly related to the Transit Interchange Project.

    Each year, the City adopts the Six-Year Transportation Improvement Program (“TIP” -- see our TIP 2020 page) which is a planning tool to identify specific projects that serve to maintain, preserve, and maximize the use of the roads and trails. Budget policy prioritizes reinvestment (i.e. preservation and maintenance projects), before constructing new facilities such as additional sidewalks and lighting. The TIP has a “New Construction Project” category that currently includes projects with new sidewalks and improved lighting. 

    Unfortunately, due to limited funding resources and competing project needs, these projects are not scheduled until 2022.  If you would like the City to consider additional project locations, we recommend submitting public comment during the next TIP process – scheduled to begin in the Spring of 2021.


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    Sound Transit and Metro project 4,200 boardings at MI Station. What assumptions are behind that number? Please confirm this number is a one-way number and does not count return trips in the evening. How many riders are projected to be boarding at South Bellevue?

    Jon Hanlon asked about 1 year ago

    Sound Transit has provided the following information about daily boardings (i.e. number of people getting onto light rail) at the Mercer Island Station: “The 2011 FEIS included a projection of 1,500 daily boardings at the Mercer Island station in 2020 and 2,000 daily boardings in 2030. A more recent projection from 2016 included an approximate 4,200 daily boardings for the current year (this is an estimate of the ridership if East Link was operational in 2016 and all ST2 projects were complete). This number does include passengers transferring from buses.”

    Sound Transit notes that “While Metro does not estimate future bus ridership at the individual bus trip or route level, the best estimate stems from the pre-Settlement Agreement East Link FEIS Addendum (April 2017) that states the following: ‘With the 77th Avenue SE Configuration, approximately 1,300 pedestrians in the busiest AM peak hour, (1,050 from bus transfers and 250 from the park & ride lot) would cross N. Mercer Way between the I-90 bus route stops located on the north side of N. Mercer Way (NMW) and the light rail station. This equates to 32 pedestrians per signal crossing cycle in the busiest AM peak hour.’” *Note the busiest AM hour is projected to fall between 6-9am on weekdays.

    Sound Transit emphasizes that it’s important to remember these are projections that fluctuate as more data and information become available. Sound Transit projects ridership using various assumptions that reflect best available information such as regional employment and population forecasts, which provide information about a specific period in time. While this information gives ST a rough idea of what it can expect in terms of ridership, there are other assumptions that can affect these numbers.

    In addition to transit integration at the Mercer Island Station, Sound Transit will also connect bus passengers to light rail at the S. Bellevue Station. While it does not yet know the exact routes and number of buses at that location (just like at Mercer Island, Metro and Sound Transit will undertake a public outreach process 18-24 months in advance of East Link opening to determine the exact route configurations), it has stated that there will be 6 bus layover spaces, 3 active bus bays and a paratransit zone.


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    Please reply: How are you overlaying "MI freeway access to WB I-90" with the Sound Transit station area planning? 80th & NMW are the access routes for many vehicles on the morning route to Seattle since the Island Crest on-ramp went away for most vehicles, requiring us to route through downtown. Please consider which route you will encourage south & central MI residents to use to access WB I-90 (in light of transit interchange planning). A planned route to minimize friction on that route will decrease stops/starts/idling & emissions.

    teampoor asked over 1 year ago

    Thank you for your question and comments. Yes, the City has evaluated the impacts to a number of intersections in Sound Transit station planning area, especially in accessing westbound I-90 following the closure of the center roadway in June 2017. Staff continue to monitor traffic patterns to ensure safe access through and around the Town Center. Currently, the most direct route for south and central Islanders to access westbound I-90 is along North Mercer Way. If conditions change along this route due to congestion at intersections, operational changes (such as signal timing) can be made to reduce delays and idling.  Other solutions, if necessary, may require capital dollars and would be evaluated and proposed in future capital improvement programs. 

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    Could the corner of 78th Ave SE and SE 24th St include an entry into the proposed roundabout? It seems like that could be a way to help mitigate the traffic on North Mercer Way between 80th and 77th by providing residents living north of NMW with an option to access Westbound I-90 and/or the town center that doesn't force them to traverse through the bus area.

    PatrickAllcorn asked over 1 year ago

    This is an interesting idea, though it would likely have some unintended consequences. Adding a north entrance to the proposed roundabout at 77th Ave would require upgrading the nearby residential streets, and perhaps trigger the need for additional property acquisition. Providing this option would likely create significantly more traffic on SE 24th Street, with drivers using this route to get to/from the Community Center and Luther Burbank Park. And any additional work outside the scope of Sound Transit's proposed configuration would need to be funded by the City.

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    I'd like to revisit the question, "Why can't overpasses be constructed for pedestrian and bike traffic that will interrupt vehicle traffic?" The response poste here seems to refer to an overpass over I-90. I'm not sure if that was the intent of the question or not. I will ask a similar question in hopes the answer may be different! It seems some safety and aesthetic mitigation is in order for a) the surge in north/south foot traffic across N Mercer Way, b) the 80th in-lane bus stop, and c) the ongoing aesthetic disturbance of bus layovers on N Mercer. I can't find these items addressed wholesale in the EIS but I am happy to be corrected. As mitigation for these items, could we have a pedestrian north/south overpass at N Mercer Way? This would keep the thousands of transit pedestrians going north/south across N Mercer Way safe and well-directed to the light rail. It is also an opportunity to appease the many residents that are legitimately concerned about the erosion of our small town aesthetic at an important point of entry to our town. This crossing is the gateway to walking to Luther Burbank Park for many mid-islanders. We have a substantial senior population relative to surrounding areas and those folks are out walking a lot with their pups! They need safe passage as do the transit users. (Full disclosure: I am a dog walker and transit user, but not quite a senior yet!) While the plantings would not need to be as ornate as the I-90 crossings, a barren concrete and metal overpass would not cut the mustard to mitigate aesthetics. Some sculpture and landscape plantings to match the sculpture park aesthetic could go a long way. Microsoft got an extraordinarily fancy pedestrian bridge, why can't our island of 25,000 residents get a low key version of that? If we could get a pedestrian bridge I can get behind the optimal solution. Otherwise the juice isn't worth the squeeze aesthetically and I think we should look beyond Metro for our last-mile solution. This has been a blend of comments and questions so I will close by asking, 1. What is the total estimated number of current and future pedestrians crossing the street at North Mercer Way at 80th? How about 77th? 2. Can we have an aesthetically pleasing pedestrian bridge across N Mercer Way at 80th to direct all of that foot traffic to a safe and aesthetically pleasing route?

    Kate A asked over 1 year ago

    Thanks for your comments. In response to your two questions:

    1) There will be an estimated 4200 boardings (people getting on the train) during commute days.  Some of these people will come from the Park-and-Ride, some will be MI residents walking, biking or getting dropped off at the station, and some will arrive by bus from the Eastside and transfer to the East Link station.  Those people arriving by bus and from the P&R will cross North Mercer at 80th to catch the train.  On the return trip from Seattle, those passengers transferring back to buses will be picked up on the south side of N Mercer Way, and will not need to cross the street again.  The main group of people making afternoon crossings at N Mercer Way will be those walking over to the Park & Ride. The greatest impact to the crosswalk at North Mercer Way/80th Ave SE will be in the morning peak hours between 6-9am.

    The 77th Ave SE entrance to the MI Station is designed to serve pedestrians, bicyclists and local drop-offs, and crossings at North Mercer Way will likely be from local foot and bicycle traffic.  Bus passengers will disembark near 80th and would reasonably walk the shortest distance to the 80th Ave entrance, and are not anticipated to walk the extra distance to reach the 77th Ave entrance to the station.

    2) Staff has preliminarily explored the possibility of a pedestrian bridge across N Mercer Way.  Pedestrian bridges get mixed reviews in terms of requiring usage by the public and other considerations, so this is not a simple solution. The City continues to explore options to address community safety concerns in this area.


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    Why wasn't Metro at the table when the 2017 Settlement Agreement was signed, and how does that give them a "pass" to deviate from the terms of the agreement now? Thank you.

    AshleyHay asked over 1 year ago

    Metro was not a party in the lawsuit between the City of Mercer Island and Sound Transit over the closure of the I-90 bridge center roadway. As a result, Metro is also not a party of the Settlement Agreement that resolved the lawsuit. The only parties to the Settlement Agreement are the City and Sound Transit.

    Metro operates buses for Sound Transit, and Metro is currently claiming that the 77th Ave SE Configuration (that the City and Sound Transit agreed to in the Settlement Agreement) will not work for Metro’s operation of Sound Transit buses. Metro has asked for changes to the 77th Ave SE Configuration. Under the terms of the settlement agreement, the City and Sound Transit are required to consider modifications to the agreed-upon Configuration based on Metro’s operational needs.


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    I have read through most of the documentation provided, and I read what appear to be references to a bus "station" but can't seem to find anything more definitive. Can you clarify whether a bus/transit station is being proposed or if any kind of sidewalk pedestrian shelters or rain screens are part of the bus interchange plans? If that is indeed the case, will more info be posted here?

    First Hill Jim asked over 1 year ago

    There isn't going to be any new structure that can be defined as a "bus station."  The transit interchange is basically just curb space where buses will pull up in front of the existing Park & Ride to allow passengers to connect to the future light rail service (opening in 2023). A roundabout will be constructed to allow the buses to turnaround more easily at 77th Ave and North Mercer Way. There may be a few additional bus shelters added. The major construction that you see in this area today at street level is to build the entrances to the East Link light rail station. As design work advances on the roundabout, more details will be posted here. 

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    Why don't Sound Transit and KCM simply skip Mercer Island on the route into and out of Seattle with nearly all the buses except for one every 10 minutes that stops on the island for those that want to get off or on there.

    bill asked over 1 year ago

    Mercer Island Station is an important part of the East Link light rail system.  Metro has already planned to completely fill the capacity for bus transfers at South Bellevue Station and cannot plan for additional routes there. Additionally, direct service to Mercer Island avoids out-of-direction travel for Issaquah/Eastside buses, and provides safer, quicker connections to/from the I-90 HOV lanes, resulting in faster bus travel times and discouraging Eastside drivers from parking on Mercer Island to reach Link light rail.

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    Will you have to demolish some houses on North Mercer Way to make the bus round about?

    k2moonka asked over 1 year ago

    The 77th Avenue SE Configuration as approved in the Sound Transit Settlement Agreement includes the construction of a new roundabout at the intersection of 77th Avenue SE and North Mercer Way, replacing the current three-way junction (or T-intersection) at this location. The roundabout construction will require Sound Transit to acquire two private properties to the north of the roundabout. Learn more about its property purchasing policies and procedures.


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    I am concerned about the impact of the roundabout and the increased bus traffic on the neighborhood north of the Park & Ride, especially to the houses that are across the street from and next door to the houses that will probably be torn down. Here are my questions: --What are the neighboring houses going to see--what is it going to look like from the neighborhood side--once the roundabout is constructed? --Is the current pedestrian cut-through going to remain? --What is the planned use for the remainder of the two lots and what will they look like? (I'm talking about the lots where the two houses are--the houses that will be torn down) --What will be done to reduce the impacts (sights, smells, sounds) of the roundabout and increased traffic? --Will there be a sound wall and/or replacement landscaping? Assuming there is a sound wall, where will it be in relation to the two lots? --How many buses will be laying over during the afternoon peak period? Where will they be laying over? --Please confirm that there are no plans to use part of the two lots as a bus parking or layover area. Thank you

    Emmy Lane asked over 1 year ago

    1.  What are the neighboring houses going to see--what is it going to look like from the neighborhood side--once the roundabout is constructed?

    The transit interchange is still in the early design stage and the design of the interface between the proposed roundabout and the neighborhood to the north has not been determined. For reference, the houses adjacent to the North Mercer Way and 77th Ave intersection are much closer today than any house will be to the future roundabout.

    Although the existing shrub hedges in the landscaped areas north of the North Mercer Way/77th Ave SE intersection would likely be removed for construction activities and revised ADA compliant trail connections, new landscaping and fencing will replace those removed. Sound Transit intends to work closely with the City of Mercer Island as the design progresses to provide appropriate buffers and screening between the roundabout/transit interchange and the neighborhood to the north.

    2.  Is the current pedestrian cut-through going to remain?

    The proposed transit interchange is still in the early stages of design and connections to the adjacent neighborhood have not been fully designed at this point. However, the conceptual plan envisions a connection of some sort between the I-90 Trail and the north neighborhood at least to the same scope of what exists today.

    3.  What is the planned use for the remainder of the two lots and what will they look like? (I'm talking about the lots where the two houses are--the houses that will be torn down)

    Plans for the property not disposed to the City of Mercer Island for the roundabout are unknown at this time (Sound Transit to retain ownership of this remaining property). However, per the conceptual design, new roadway features will allow for a number of additional landscaped areas; the entire north side of the roundabout will have an approximately 5-foot planter, allowing for the installation of new (or existing) trees/shrubs to separate the I-90 Trail and the proposed roundabout from the neighborhood to the north. Sound Transit intends to work closely with the City of Mercer Island on redevelopment that is compliant with local zoning codes and development plans.

    4.  What will be done to reduce the impacts (sights, smells, sounds) of the roundabout and increased traffic?

    The proposed roundabout will not result in an increase in traffic; in fact, the total number of buses on Mercer Island will not exceed existing numbers and will be reduced by almost half due to the Settlement Agreement. The proposed roundabout was analyzed during the environmental review process.

    5.  Will there be a sound wall and/or replacement landscaping? Assuming there is a sound wall, where will it be in relation to the two lots?

    The transit interchange is still in the early design stage and no decisions have been determined at this time. Sound Transit intends to work closely with the City of Mercer Island as the design progresses to provide appropriate buffers and screening between the roundabout/transit interchange and the neighborhood to the north.

    6.  How many buses will be laying over during the afternoon peak period? Where will they be laying over? --Please confirm that there are no plans to use part of the two lots as a bus parking or layover area.

    The exact number of buses laying over during the afternoon peak are not known at this time. Metro will be updating its service plan for this area much closer to the start date of East Link revenue service in 2023. Per the proposed configuration, buses will lay over on both the north and south sides of North Mercer Way to the east of the proposed roundabout; the amount of curb space available for buses would allow up to 4 buses laying over at any given time. There are no plans to use the two lots for additional bus layover or bus parking areas.