I decided to move over to the BGE for a while to learn about some of it’s features. I found some good tutorials that show how to make some simple (non-violent!) games, and one of them that I really like and want to expand on is a car racing game.
I have created a huge subdivided plane to use as a terrain (70,000 faces), and I can pull it into hilly shapes easily enough, but I really want to create something smoother, with very slight rises and dips like on a real road. I know of various ways that I could do it, such as applying sub-surfs or using proportional editing, but I want to know how YOU would do it for quick and simple terrain.
You can make the roads as a separate object. (Perhaps mesh from a bezier path? Nice even curves and slopes that way.) And then put a shrink-wrap modifier on the terrain, project on Z-axis to the road mesh object. Parts that overlap the road will snap to it. But the rest will remain how you sculpted it.