Back in my crazy younger days, I used to compete in overnight winter car rallies on amazing twisty and icy roads. There were minimal instructions, only warning of particularly nasty corners. You were expected to maintain a target average speed, while driving "blind" (i.e. no prepared stage notes, just navigating what you see coming.) You get penalized for arriving late, or early, at surprise checkpoints along the way. The problem is, with the many blind crests and tight corners, you often couldn't see very far at all.
I sometimes relied far too much on glancing at my GPS display to warn me of any upcoming hairpins. As long as the GPS showed the road continuing relatively straight over this next blind crest, then I'd risk taking it at a bit more speed. I got a huge fright once when I suddenly realized the GPS display had frozen and wasn't updating because it lost satellite reception due to the heavy snow cover in all the trees overhanging the road. The display had been showing the SAME straight section of road all this time, and any one of these blind crests could just as easily have been followed by a sharp curve, and we would have launched off the road. Eek.
Here's a sample from before I even had a GPS.