Sounds like an interesting project that you've got going on! Hope to see screenshots of it someday.
Also, I'm definitely interested in your methods for building Interstates in Surveyor. Whenever you get the chance to write your methods down, send them to me in a PM. Thank you so much for your...
I second this suggestion. A significant portion of a route I'm working on runs parallel to an Interstate highway and a handful of its interchanges. At the time of writing this I'm using the YARNish assets to represent this Interstate; they look and work great!
Seeing this thread dates back all the way to 2008, it's highly likely that the aforementioned route is now vaporware.
Don't know of any rendition of the Water Level Route that is available. It is certainly a route I would like to see done well.