I've never heard the term "Blue Roads" before, must be a local term, kind of like the term "toboggan." In some locations it means a sled you ride on in the snow, in other locations, it means hat you wear on your head. I grew up with the "hat" definition, never knew it meant a sled until I was 24 years old!
Anyway, so much for "history."
I don't know about percentages, all I know is, people drive like insane idiots on interstates! And the heavier the traffic, the more insane they become. Around where I live, the interstates are horrible, bumpy, and always under construction which causes people to drive even more insane, regardless of posted signs about fine increases and even video patrolling speeding tickets! Because of these issues, we avoid interstates as much as possible.
When traveling, we now never get in a hurry. We both enjoy driving. And I do enjoy "cruise control" on interstates, especially at night, if traffic is not insane. But we've found the "secondary roads" (Blue roads?) are much more friendly, there's so much more to see, and there's more chances to find something off-the-wall and just stop in for a few minutes and smell the local culture.
Ever since we've slowed down, take the secondary highways, and even back country roads sometimes, we've seen a LOT more and experienced a LOT more! We've seen some pretty fantastic scenery, some really interesting little towns and villages, all kinds of land marks, and visited numerous Mom & Pop stores along the way, fruit stands, and even events.
A few years ago, we were driving through this small town (to deliberately avoid the interstate), when we came upon an intersection. Just as we got RIGHT there, a policeman jumped in front of us and stopped traffic. And there it came! The 4th of July parade! We got to sit in our truck (with trailer behind), right at the intersection and watch the entire thing. Granted, we had no idea what little town we were in, but sure was pretty cool! And we had the luxury of sitting in our own vehicle with air conditioning, drinks, and a spectacular view of the parade. Did we get upset? Absolutely not! We thoroughly enjoyed the moment and celebrated with this small town! You don't get that from the interstate! Share this story with your husband please.