SR 9 - 108th St NE - Intersection Improvements

Project News


WSDOT contractor crews from Granite Construction are installing a single-lane roundabout on State Route 9 at 108th Street Northeast in Marysville to 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 is WSDOT installing 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.

Closures and detours

This project required two weekend-long closures of 108th St NE at SR 9 to install the roundabout. One closure was completed in late September 2019. The other was completed in July 2020.

During closures of the intersection, posted signs will route drivers along an 8.3-mile detour.

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.

Needs & benefits

  • Safety: The roundabout will reduce the severity of collisions.
  • Congestion: The improvement will help the flow of traffic and reduce wait times at the intersection.
  • Environmental: Shrinking wait times reduces vehicle idling, which may help air quality.


  • Summer 2018: Construction began.
  • Fall 2018: Project suspended until spring 2019.
  • Spring 2019: Project resumed.
  • Fall 2019: First weekend closure completed.
  • Fall 2019: Project suspended until spring 2020.
  • Spring 2020: Construction resumed.
  • Fall 2020: Construction expected to be complete.


Financial Data for PIN 100924C
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $3,481
CWA $0
Total $3,481


Frances Fedoriska
WSDOT Communications

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.