Cross-posting a little here, I think.....

Rob, it is not a "simple fix" that someone can easily incorporate into the next release of Vue.  

If we want to get technical about it,  it is possible to begin with a "heightfield map" for a terrain, (you're probably familiar with the concept of a heightfield map?), and then use a network analysis algorithm and quite a lot of the programming tools that go with that, to "plot" an optimal path across that heightfield (actually, just a table of height values) that would describe where the road would lie. A familiar technology for any of us with a technical geographic information system background.... And then, using various other procedural tools, actually form up the road modelling segments.  But these are technologies costing hundreds of thousands of dollars, and they require high order technical skills to implement. Not something that someone is going to just plop into the next version of Vue.    (Laughing, and I don't want to do it - a kind of work I did for years and hoped to have retired from forever.)  But this is why I'm sharing this with you. Having worked with the kinds of analyses and programming needed for this, I concluded that we don't want to go here.  This is not an appropropriate path to take for several years - at least not for a piece of software like Vue that is must be priced at under $5K per copy.