Sometimes there are no alternative routes. Our goal was to ride US highway 20, the longest contiguous route from Newport, OR to Boston MA. Sometime the route was quiet relaxing riding, some was freeway, and some riding was on good frontage roads.
An 54 mile stretch between Boise and Mountain Home, Idaho.
I am a loyal ACA member, but I take their route maps with a grain of salt. We met an ACA supported tour group in northern Michigan. They were heading in the opposite direction, when we stopped to talk to their leader. He gave us a section of the route map they had just finished. We followed it for a short section heading south along the Lake Michigan shore. It started raining, as the map routed us off the road we were on and up a long hill into a small town. Riding downhill on the other side of town, we were routed back to the junction of the road we just left. Then it started raining harder. From that experience I like to use tools like google map to check some of their route directions. We really did not have to go up that hill.