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State Route 9 Corridor Program


  • Through 2026, WSDOT will invest more than $211 million in Connecting Washington funding to continue improvements on SR 9.
  • For more information about completed and current planned projects, take a look at the SR 9 corridor project pamphlet (pdf 855 kb).
  • Sign up for weekly e-mail updates on our construction projects in Snohomish County.
                                                           SR 9 Map
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SR 9 Snohomish Corridor MapState Route 9 extends 98 miles, from SR 522 north of Bothell to the Canadian border. The highway parallels Interstate 5 to the east as it winds through Snohomish, Skagit, and Whatcom counties.

Growing population, increasing congestion
Due to regional economic development and the demand for affordable housing, the population of Snohomish County increased by 111 percent between 1980 and 2010. 

Congestion-related collisions - like rear-end and sideswipe collisions - have also increased along SR 9. From 2000 to 2003, there were an average of 395 collisions per year on SR 9 in Snohomish County. Between 2004 and 2007, that average had increased to almost 480 collisions per year.

Improving safety and reducing congestion

Since 2000, WSDOT has invested nearly $300 million to transform SR 9 into a wider, safer highway. We have widened the highway to four lanes in some areas, added turn lanes at key intersections to reduce the risk of collisions, installed divided medians at select locations to prevent crossover collisions, and upgraded pavement markings, guardrail, drainage, culverts and lighting where needed. 

These targeted improvements have helped relieve congestion, improve traffic flow and enhance safety throughout the SR 9 corridor.

Current SR 9 improvement projects under way include:

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