When I ask Google Maps for Ashford to Sedro-Wooley, it gives a 150 mile route with time estimate ranging from 2hr 40min to an hour more.
One choice in the south is between WA7 (via Spanaway) and 161 (Puyallup). Both have twisty sections in the south, and suburban business in the north before hitting the freeways. The other choice is between I5 and I405, about the same.
If I tell it to avoid freeways, and drag the route to Snoqualmie, it adds 10-15 miles, and a hour to the route.
I like the drive through the Snoqualmie valley. I was just out there checking out a 30 mile bike trail. But if my goal was to get from one end to the other, as opposed to sightseeing and poking around, I'm not sure that avoiding the freeways is worth it.
With the mountains to the east, and Sound to the west, there aren't any fast outer beltways around the metro area.
North of King Co, WA9 is the main alternative to I5. But that doesn't get into country until north of Arlington. And after that there are windy sections. Often I leave the freeway at Arlington, and head east to Darrington and then north to WA20, bypassing the town driving at the west end of 20.
If I change the destinations to Packwood and Winthrop, it takes me east to US97 and north, adding 100 miles, and estimated time of 5 hr. I like that drive, but that's basically a full day's travel.
