I was wondering the same thing so did some research on the Washington State Department of Transportation website and here is what I found:
This project in both directions of I-90 will be adding capacity to the roadway. They estimate the improvements will provide relief for almost 150,000 travelers who use this stretch every day.
The projects main objective is to add auxiliary lanes and build sound walls to minimize the effects of road noise.
What is an auxiliary lane and how will it help? The auxiliary lane is an extra lane added between closely spaced interchanges which gives drivers more time and space to enter or exit the roadway. They will be located on the outside of the existing lanes in both