I stayed as far right as possible on I-90, and the shoulder was not strewn with debris. That part of the highway was lightly trafficked, at least on a Sunday morning. But as noted, you’re going to have some noise.

What I didn’t mention was that in 2019 two of the I-90 sections I had to ride were closed to motor vehicles in preparation for upcoming roadwork. You don’t know fun until you’ve literally had an Interstate all to yourself.

OP: Are you planning on doing the NorPac Trail from Mulan? If so, you need to know that the Borax Tunnel east of Lookout Pass is (last I heard) barricaded due to the fear of imminent collapse. Supposedly, there is a difficult hike-a-bike way around, but I can’t confirm that.