One of the largest ever design-build projects for the Washington State Department of Transportation, this project will reduce congestion for drivers on Interstate 405, a main artery for Seattle’s eastern suburbs. Key parts of the project include constructing 12 miles of express toll lanes on the interstate between State Route 167 in Renton and Northeast 6^th Street in Bellevue. It connects into a 40-mile system of express toll lanes, and supports the new I-405 Bus Rapid Transit System. Drivers will see a significant reduction in traffic congestion as a result of the new toll lanes. 

More than 40 bridges will also be replaced, widened or undergo rehabilitation as part of the project. Plans have been developed to avoid completely replacing certain bridges, reducing cost and traffic impact on the busy 405 and surrounding roadways. Existing bridges along project will be brought up to current seismic standards.

The project will also be beneficial to area wildlife as well, with culverts being replaced with more environmentally beneficial fish passages.

In order to disrupt the travel of motorists as little as possible, a maintenance of traffic plan has been developed to allow for large work zones that will minimize traffic shifts. Flatiron is also part of an effort to provide a smooth rollout for the new express toll lane system.

Work on 14 miles of roadway, including 12 miles of express toll lanes to ease traffic.

Connects into a 40-mile system of express toll lanes, and supports new I-405 Bus Rapid Transit System.

Existing bridges along project will be brought up to current seismic standards.