In many areas, they only way to cross rivers is on the Interstate system (no bikes allowed) without long detours of many miles. As an example, some of area I would like to include in a tour are on opposites sides of a river with no non-Interstate crossing for a 100 miles or so. On very long tours, alternate route planning is a very viable solution. However, on shorter tours, it is not an answer if it defeats your desired itinerary.
How do you handle that on tour between two points when an Interstate crossing is the only reasonable solution?