Brendon Pywell is the guy who made the fantastic Bob's Track Builder. Unfortunately that software is pretty much outdated and he seems to know that as well. Instead of trying to hold on to it, he just created something new and... well, take a look at that:



You can import a complete area from Google Maps and just add polygons via a brush.
This looks like the mightiest tool to create tracks so far, fast and easy.

Steam Greenlight page: http://steamcommunity.com/sharedfiles/filedetails/ ?id=447605480&insideModal=0&requirelogin=1