12th Ave NW & SR-900

12th and SR-900

Project Overview 

This project will widen the northbound SR 900/17 Avenue NW approach to 12th Avenue NW to construct an exclusive right-turn lane and widen 12th Avenue NW approach at SR 900/NW Sammamish Road to provide an additional left-turn lane for added capacity.

Improvements will also include new protected bike lanes, wider sidewalks, landscaping, trees, and illumination on both sides of 12th Avenue NW. 


Construction on 12th Ave NW is nearly completed.

  • The road has reopened to two way traffic
  • Repaving, new sidewalks, bike lanes, and landscaping are completed

Due to delays in arrival of the new traffic signal poles, work at the intersection is not yet complete.

The project will be on hold until the new traffic signal poles arrive (likely late February 2024). When the new traffic signals arrive, construction work at the intersection will then resume until the project is complete.

Until the work at the intersection is completed the new right turn lane on SR 900/17th Ave NW and the additional left turn lane on 12th Ave will remain closed. The pedestrian detour at the south corner of the intersection will remain in effect. 


Roadway network updates are necessary to improve overall traffic circulation north of I-90. These improvements help reduce the number of intersection accidents by providing the dedicated right-turn lane from SR 900/17th Avenue to 12th Avenue. The project will also help reduce the number of vehicles waiting to turn left from 12th Avenue at any given time by providing and additional left-turn lane.

The project is also a corridor identified in the City’s Walk and Roll Plan to increase accessibility for pedestrian and bicycle traffic and connect existing non-motorized facilities throughout the City. This project is included in the Central Issaquah Area Plan, the City's Concurrency Capacity Projects list and is part of the Costco Development agreement. The project is partly funded by a Transportation Improvement Board (TIB) grant.

Project Timeline

  • Fall 2021: Design completion and permitting
  • Early 2022: Project bid and award
  • April 2023: Construction begins
    • April-August 2023: Stage 1 Construction – work on south and west side of 12th Ave
    • August-November 2023: Stage 2 Construction – work on north and east side of 12th Ave
  • November 2023: Work completed on 12th Ave
  • January/February 2024: Construction on hold until new traffic signals arrive.
  • April 2024: Anticipated construction completion  

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