A good road with much lower traffic than 30 or 26. Initially out of Longview west...take Industrial way all the way to west Longview and SR 4 (i.e., don't turn south on to the Ranier Bridge, head straight west (and avoid Ocean Beach Highway in west Longview). SR 4 can have a few to many log trucks and a few areas with tight shoulders. One hilly area over Little Cape Horn to Cathlamet. Cathlamet to Ferry has one bridge, a bit tight and not quite 1/2 mile long but its a real low use area so shouldn't be any issues. Ferry is nice.

Best tool for checking out a Wa state road.

http://srview.wsdot.wa.gov/srweb/srweb.htm start on SR 4 Mainline and go to last photo at bottom (otherwise your in Willapa Bay at the real "start" of SR 4) then jump ahead in 100/100 increments, or pick a cross street from a map and jump to it. I started at Coal Creek then flipped ahead a few miles for this view.

here's a view west of Longview.