Google Street view is terrific for reviewing potential routes.
Oregon has cycling routes. From Hillsboro (West of Portland) to the coast has three charming ways shown. Well in most places you have a nice wide shoulder, lots of room. Speeds still posted at 60 mph, so you have to use caution, but in areas, those routes are narrow bridges. Long bridges, no shoulder, so you have to mantain your lane and pedal as hard as possible to avoid backing up too much traffic.
It's interesting to look at Garmin routing and Strava Heatmaps.
Of course, Google Street View won't help if you are touring Germany (privacy laws don't allow such a thing) but was fun to look at cycling routes near Stuttgart to see what Google came up with (most off the main road, but locals know the back ways which Stava will show).