Carson, your post is one of the most inteesting ones for some time. After riding a few miles this morning I decided it deserves more attention. I live here on the east coast near the space center.
I am sure that my comments about the U.S. road system will not apply to other countries.
Route planning was one of the big obstacles that I had to overcome on my first cross country tour. I had no touring experience and no real understanding of how it would be riding a bicycle on our highway system. I read Ken’s site and his words about route planning. I ended up buying the first two Adventure Cycle maps for the Southern Tier west out of San Diego. After studying those maps, I then planned the rest of the route with AAA maps. Some of my choices turned out great, some did not. Last year my cross country began with all AAA maps and a made up routing from here in Florida to Kansas where I picked up the ACA TransAm routing which I followed mostly for the rest of the trip. I have decided that when the road I chose sight unseen turns out to be one I don't like, well, that is just part of the experience. Then I figure out another route that works.
Some of my thoughts for route planning when I know nothing about the roads involved are:
1. Do not get on a County or State road that has no shoulders unless the traffic is very light and visibility for me and the cars is good. Small narrow roads that have a lot of blind curves are not good because the cars can’t see you and you can’t see them. After a day or two of diving into steep ditches avoiding logging trucks, this has become my most important rule.
2. Plan to follow a U.S. highway when possible. They always have either paved shoulders or unpaved shoulders if need be. They will probably have more traffic than some roads but you can get out of the traffic pattern. Only a couple of times have I been on a U.S. highway and the paved shoulder quit. That can be a problem because of the heavier traffic. Both times I was able to ride on the unpaved, grass shoulder until I could find a secondary road that worked for me.
3. Use the Interstate highway system if it is available, suits your purpose, and it will connect you with a U.S. highway that is headed your way. But check the local State laws. Some states it is legal (Claifornia, Arizona, New Mexico, Oregon for example), some places it is not legal (Florida, and Kansas for instance). The shoulders on an interstate highway are very wide and I feel safe as long as I am not in city traffic where it is almost always illegal in any event. You will find that the ACA routes use the Interstate system in several instances.
4. I usually approach cities with some trepidation since you never know what the road you are on is going to be like. I never hesitate to bail out and get on the sidewalk. I spend miles riding on sidewalks just to stay out of the traffic. I know that people here say sidewalks are dangerous, well so are busy city streets when there is no shoulder or bike lane. Just take your time in the city, watch for cars coming out of parking lots, etc. and the sidewalks will provide you a real escape and keep you moving through the city.
5. Trust me, when you get out west where the population density is low and the traffic is also low, you will find the quiet roads that go for miles without seeing cars for 1/2 day or more.
Good luck and have a good ride.