SR 9 - 108th St NE - Intersection Improvements - Complete October 2020


WSDOT contractor crews from Granite Construction completed installation of a single-lane roundabout on State Route 9 at 108th Street Northeast in Marysville in October 2020. The roundabout will reduce wait times and collisions at the intersection. This project was combined with a nearby paving project on SR 92, that filled existing potholes and cracks from 147th Avenue Northeast to Quarry Road.

Why did WSDOT install a roundabout on SR 9 at 108th Street Northeast?
About 16,000 drivers use this intersection every day. Nearly 1,500 of them are attempting to turn from the stop signs at 108th onto SR 9. Trying to turn from a stop onto a highway increases the risk of collision, including rear-end crashes, the most common type at this intersection.

Between 2012 and 2017:

  • More than 50 people were injured in 28 collisions at SR 9 and 108th St NE.
  • Ten collisions were rear-end crashes.
  • At least six of those collisions happened at the stop signs on 108th St NE.

A roundabout greatly reduces the need to stop to make left turns, allowing traffic to move freely. The Puget Sound Regional Council forecasts the number of average daily travelers on this stretch of SR 9 will increase to 17,000 in two years, and nearly 19,000 in 2030. Community Transit’s 2030 long-range plan (pdf 4 mb) also identified this corridor as a route needing more commuter bus service for the growing population.

The End Result

The new roundabout will reduce the severity of collisions and wait times at the intersection. 

  • The Insurance Institute for Highway Safety (IIHS) and Federal Highway Administration (FHWA) studies on roundabouts show they typically reduce injury crashes by 37 percent.
  • The IIHS and FHA also found a 90 percent reduction in fatalities at intersections with roundabouts compared to intersections with no improvements.

Get more information on the benefits by visiting our roundabout page.


The cost of this project was $4.031 million.


  • Summer 2018: Construction began.
  • October 2020: Construction completed.


Northwest Region Communications
15700 Dayton Ave. N.
Seattle, WA 98133


In 2018, contract crews will install a single-lane roundabout at SR 9 and 108th Street Northeast.

SR 9 at 108th Street Northeast
Before this project began, the west side of the intersection on 108th St NE at SR 9 was about 4-feet too high. During a weekend-long closure in 2019, this hill was reduced to give drivers a better view of the roundabout entrance.