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9611 SE 36th Street
Mercer Island, WA 98040
Phone: 206.275.7600
Fax: 206.276.7663
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R8A: Adding HOV Lanes to the Outer Roadway


A visualization of the new HOV Lanes to be added to I-90, with light rail occupying the center roadway
I-90 currently has a two-lane reversible center roadway carrying express lanes between Seattle and Bellevue for buses, carpools, vanpools and Mercer Island vehicles only. Weekday traffic is routed westbound in the mornings and eastbound in the evenings on the center roadway.

The center roadway between Mercer Island to Seattle is 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.

Buses, carpools and vanpools that need to travel counter to the center roadway flow are forced to use general-purpose lanes on the outer roadways, making them run increasingly late during rush hours due to congestion. In order to address this transit efficiency problem and also prepare for light rail, WSDOT and Sound Transit are implementing 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 and off-ramps on Mercer Island and modified I-90 HOV access at Bellevue Way. The City is currently negotiating future access to these new lanes for Mercer Island traffic.

When these improvements are complete, Sound Transit will be allowed to close the center roadway permanently to vehicles in order to begin construction of the East Link light rail line, expected to open in 2023.

View a diagram depicting the future I-90 lane layout across the floating bridge

The closure of the center roadway will create some temporary adjustments for residents during construction, and will also lead to permanent changes in HOV on/off-ramp alignment, traffic patterns, bus access, and other transit-related matters.

View a summary diagram of major on/off-ramp changes expected in the Town Center Area
View a summary list of all expected ramp changes

The City is currently negotiating with regional and federal agencies over what these changes might look like, in order to gain the maximum transportation benefit possible for its citizens while minimizing undesirable changes to residents’ daily routines.

See below for FAQ



If you have questions that aren't answered in the FAQ, please use the online comment form.
Verbatim comments to date will be available soon.

Or contact Kirsten Taylor, Assistant City Manager, by Email at:


What's Happening Now

NEW: On February 13, 2017, the City Council voted to take legal action that would seek to temporarily halt 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.

Outreach presentations and events began in 2016 and are continuing.
Visit the Light Rail Mobility and Outreach page for full schedule.

Access to Future R8A Lanes
On August 5, 2016, the City received a letter from FHWA denying Single Occupant Vehicles (SOV's) access to the future R8A Lanes and the Island Crest Way westbound on-ramp; read the City's full press release here.  The City is in ongoing discussions with the Federal Highway Administration (FHWA) regarding access policy for Mercer Island traffic to the future R8A HOV lanes; read all historic correspondence here.

Loss of Mobility Negotiations - Learn more here
In addition to the R8A issues, the City is also holding related mitigation discussions with Sound Transit regarding loss-of-mobility concerns due to the closure of the center roadway and the impacts of light rail construction. 

Currently WSDOT is building Stage 3 of its workplan - Learn more here
This will install a westbound HOV lane, from 80th Avenue on Mercer Island to Rainier Avenue in Seattle, and an Eastbound HOV lane from Rainier Avenue to 77th Avenue SE on MI. Work also includes fire and life safety upgrades in the Mt. Baker tunnel and the Mercer Island Lid tunnel; and an eastbound HOV direct-access exit ramp (via existing tunnel) to Island Crest Way on Mercer Island.


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 public outreach events began in 2016 -- check the Light Rail Mobility Discussions page for more detail.


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)

Recent R8A 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


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