Yes, US2 from Monroe through can be congested, with commuter traffic along with the people heading into the mountains. Seems the most of traffic fatalities are result of someone cross the center line, a hazard on any 2 lane highway. I don't let that deter me.
But in my experience WA20 from the freeway through Sedro-Woolley (about 7 miles) feels just as congested. Often I like to bypass that by leaving the freeway at Arlington, and taking 530 through Darrington. That stretch by itself is scenic and worth the drive. Or in the right vehicle, exit to Granite Falls and take the Mountain Loop Hwy to Darrington - with 15 miles of gravel forest service road!
US2 Leavenworth to Wenatchee is also pretty busy, though about half is divided.
WA20 is more remote. The 70 miles Marblemount to Mazama has no gas.
Take one, and back on the other!
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