Much of Namibia is very very flat. While the road does go up and down a little bit, it's mostly not by more than a couple feet. Of course there are areas that are not flat at all, but for the course of much of my driving, flat was where it was at.
There's also a bit of a rail network, mostly for freight. I don't think there's more than a train a day going on these tracks, but if you're lucky, you'll eventually spot one.
Section of the TransNamib railway network.