I-405/I-5 Operational Improvement, Northbound Auxiliary Lane Project

Project overview

The project will make improvements in Lynnwood and nearby unincorporated Snohomish County to reduce the traffic backup that often builds up on northbound I-405 near the I-5 interchange in Lynnwood during the afternoon. The project will create an auxiliary lane between the northbound I-405 on-ramp and the 164th Street Southwest off-ramp along northbound I-5. An auxiliary lane is an extra lane, typically between an on-ramp and the next off-ramp, that helps drivers merge and exit more smoothly. The ramp from I-405 to I-5 will be modified to maintain two lanes for the entire length. The project will also build a new noise wall along southbound I-5 and repave sections of the highway.

What to expect

We are currently in the design phase of this design-bid-build project. We expect to hire a contractor in 2027 as we move toward construction. Once a contractor is hired, we’ll be able to share more information about the construction schedule. We expect construction to last about one year. 

Environmental Justice Assessment

Washington's environmental justice law, known as the Healthy Environment for All (HEAL) Act, requires us to conduct environmental justice assessments when considering significant agency actions, like this project. 

This environmental justice assessment will help us understand the potential environmental and health impacts of this project, specifically on vulnerable populations and overburdened communities. 

Environmental justice in Washington, as provided in the HEAL Act, addresses disproportionate environmental and health impacts in all laws, rules, and policies by prioritizing vulnerable populations and overburdened communities, the equitable distribution of resources and benefits, and eliminating harm (RCW 70A.02.010).