US 12 - Anderson Rd - Safety Improvement

Project news

  • WSDOT initially planned to build two roundabouts on US 12 at the intersections of Anderson Road and Moon Road SW. However, the Moon Road roundabout became unnecessary following Thurston County’s intention to close a portion of 188th Avenue SW. 

Why is WSDOT planning changes to the intersection of US 12 and Anderson Road?
WSDOT explored alternatives to help reduce the potential for collisions. After thorough review and analysis that incorporated public input, the decision was made to build a single-lane modern roundabout at the intersection. Modern roundabouts provide a cost-effective and efficient solution to keep traffic moving while reducing the likelihood and severity of collisions.

Anderson Road
Anderson Road south of US 12 is the main entrance for visitors and freight traveling to and from properties owned and operated by the Confederated Tribes of the Chehalis Reservation. WSDOT is proposing to construct a three-leg modern roundabout at this location. This roundabout will be large enough to accommodate emergency vehicles, farming equipment, log trucks and other semi-trucks with trailers.

This proposal will permanently close access to Anderson Road north of US 12. Drivers who use that roadway will be able to reach US 12 via Sickman-Ford or Moon Road Southwest. Anderson Road south of US 12 will remain open.

Roundabout Benefits
Studies have shown roundabouts in certain instances have the potential to reduce the number of collisions when compared to stop signs or traffic signals. Roundabouts also help save limited state resources since they do not require ongoing maintenance such as the work required for traffic signals.

The End Result
Crews will build a modern single-lane roundabout at the intersection of Anderson Road. The roundabout will enhance mobility and travel through the area.

Needs and benefits

  • Improved traffic flow – Roundabouts are designed to promote a continuous, circular flow of traffic.
  • Saves money – Reduced maintenance and repair costs.
  • Accommodates all vehicles - Including farm, freight, and log trucks
  • Provides access for pedestrians and bicyclists


  • Aug. 2016 - WSDOT open house
  • Spring 2019 - Project advertised for competitive bidding
  • Spring/summer 2020 - Construction 
  • Fall 2020 - Project complete


Financial Data for PIN 301201G
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $3,018
CWA $0
Total $3,018


John Romero
WSDOT Project Engineer

Doug Adamson
WSDOT Communications

US 12 Anderson Road-Safety Improvement Project Vicinity Map