SR 18 - Issaquah/Hobart Rd to Raging River Br - Widening

Project news

  • The Legislature has provided funding to begin design work on widening SR 18 between Issaquah-Hobart Road and Raging River. There is no funding for construction.
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Needs & benefits

SR 18 is a crucial highway that moves thousands of people and serves as an important truck route between western and eastern Washington. Although most of SR 18 is within protected forestlands, the number of vehicles using the highway has increased as cities and businesses on either end of SR 18 have grown significantly. This has resulted in more congestion and an increase in collisions.

A 6-mile section between Issaquah-Hobart Road and Raging River has just one lane in each direction, with the exception of occasional truck-climbing lanes. When funded for construction, we will widen this section of the highway to provide two lanes in each direction with a center median or barrier.

Widening the highway presents several challenges. There are up to 17 fish culverts under the roadway that may require replacement. Many wetlands must be protected or replaced.

Improving the highway will have several benefits:

  • Reduced congestion and better travel times.
  • Reduced risk of collisions following installation of a center median or barrier.
  • Upgraded fish passages will provide better habitat for fish and provide additional wildlife crossings.


  • 2019: Design work and community engagement.
  • Fall 2020: Deliver widening report and cost estimate to State Legislature.
  • Fall 2021: Design work complete.


The Washington State Legislature provided $26 million in the 2019-2021 biennium for developing a construction cost estimate, design and right-of-way acquisition.



Kris Olsen

A small map showing the section of SR 18 between Issaquah-Hobart Road and Raging River Bridge in King County, Washington.
Project map area

 A small photo looking east on SR 18 that shows one lane in each direction at the bridge over Issaquah-Hobart Road
Looking east on SR 18 near Issaquah-Hobart Road