City of Mercer Island, Washington - Home City of Mercer Island, Washington - Home Facebook Twitter YouTube
site map
Back to City and Regional Projects

Operating & Capital Financial Challenges
Light Rail (East Link)
I-90 Issues
R8A: Adding HOV Lanes
Comment Form
I-90 Bike Trail Work
I-90 Tolling
I-90 Document Archive
Sound Transit Park-and-Ride
Residential Development Standards Update
Mercer Island Center for the Arts (MICA)
Capital Improvement Program
Street, Pedestrian & Bicycle Facilities
Transportation Improvement Program (TIP)
Transportation Benefit District
Renton Municipal Airport

Calendar Events
RFPs & Bids

9611 SE 36th Street
Mercer Island, WA 98040
Phone: 206.275.7600
Fax: 206.276.7663
Notify me by Email
R8A: Adding HOV Lanes to the I-90 Outer Roadway (Complete)



A visualization of the new HOV Lanes to be added to I-90, with light rail occupying the center roadway
WSDOT and Sound Transit have completed the R8A plan to add new HOV lanes alongside the general purpose lanes of the I-90 outer roadway between Seattle and Bellevue. WSDOT has also built new I-90 HOV on-ramps and off-ramps on Mercer Island and modified I-90 HOV access at Bellevue Way.

With the completion of these modifications, WSDOT closed the I-90 center roadway permanently to vehicles on the weekend of June 3, 2017 in order to allow Sound Transit to begin construction of the East Link light rail line (expected to open in 2023).

The closure of the center roadway will create some temporary adjustments for residents during construction (e.g. Traffic Control measures), and will also lead to permanent changes in HOV on/off-ramp alignment, traffic patterns, bus access, and other transit-related matters. View a diagram depicting the new I-90 lane layout across the floating bridge.

View a diagram of major on/off-ramp changes expected in the Town Center Area (as of May 19, 2017)
View a summary list of all expected ramp changes

See below for FAQ


If you have questions that aren't answered in the FAQ, please use the online comment form.
Or contact Kirsten Taylor, Assistant City Manager, by Email at:


Latest News

On February 13, 2017, the City Council voted to take legal action that could have temporarily halted the closure of the I-90 center roadway to provide the City, the Washington State Department of Transportation (WSDOT) and Sound Transit the ability to continue their ongoing negotiations about preserving mobility and safety for Mercer Island residents. Read the full press release.  

On May 31, 2017, the City Council accepted a tentative settlement offer of $10.05million in mitigation payments from Sound Transit, and the lawsuit was suspended.

Access to W/B I-90 via Island Crest Way for SOVs
On August 5, 2016, the City received a letter from FHWA denying Single Occupant Vehicles (SOV's) access to the new HOV Lanes and the Island Crest Way westbound on-ramp; read the City's full press release here. In response to appeal by the City, another letter rejecting SOV access was sent by FHWA on May 23, 2017.

As of June 2017, SOV access to the Island Crest Way tunnel westbound I-90 on-ramp is no longer permitted. The City is in ongoing discussions with the Governor, WSDOT and the State's Congressional delegation over legislation to request an exemption that would allow SOV access; read all historic correspondence here.


Frequently Asked Questions (FAQ)

Read the latest FAQ documents


Get Involved

A series of public input opportunities occurred in September and October 2015; click here for presentation materials and summary comments from Sound Transit's Mercer Island webpage.

Additional related public outreach events began in 2016 -- check the Light Rail Discussions and Outreach page for more detail. Note that future outreach will likely focus on the actual construction of light rail and the Mercer Island station.



The modern I-90 was built with a two-lane reversible center roadway carrying express lanes between Seattle and Bellevue for buses, carpools, vanpools and Mercer Island vehicles only. Weekday traffic was routed westbound in the mornings and eastbound in the evenings using the center roadway. The center roadway between Mercer Island to Seattle was technically considered Express Lanes rather than High Occupancy Vehicle (HOV) lanes; both types are considered versions of "managed lanes" versus "general purpose" all-access lanes.  These lanes have been replaced by the R8A project; see details below.

"R8A" HOV Lane Construction Details
Stage 1 Westbound HOV lane, Bellevue Way to 80th Avenue SE (Completed October 2008)
This stage added a new HOV lane in the westbound I-90 outer roadway between Mercer Island and Bellevue.  It also built a new HOV direct access ramp at 80th Ave SE and modified the pre-existing Bellevue Way HOV direct access ramps for two-way transit operation.
Stage 2 Eastbound HOV lane 80th Avenue SE to Bellevue Way (Completed March 2012)
This stage provided an HOV lane on eastbound I-90 between Mercer Island and Bellevue.  It also modified the existing reversible HOV ramp at 80th Ave SE on Mercer Island to a HOV on-ramp connecting directly to the new eastbound HOV lane and it extended the eastbound I-90 to I-405 auxiliary lane and modified the Bellevue Way & I-405 HOV direct access from the eastbound HOV lane.
Stage 3 Continue HOV lanes across both directions of floating bridge (Completed May 2017)
This stage also updated life-safety systems in Mt Baker and Mercer Island tunnels, and adds an eastbound HOV direct-access exit ramp (via existing tunnel) to Island Crest Way on Mercer Island.


Additional Resources

Supporting Documents
Click here to view the full archive of I-90 supporting documents, including agreements about the use of the center roadway bridge.

Click here to view the presentation made to the City Council on January 7, 2013 regarding the Two-Way Transit and HOV Operations Project (R8A)


City of Mercer Island Washington | All Rights Reserved 2020| Privacy Policy | printer friendly version Printer friendly version | Site Handcrafted in Ashland, Oregon by Project A