they put on the sides of freeway specifically for moments like this.
We had been down in Mexico for a trip and were driving home. I drove the entire way and then got tired the last hour and asked her if she could drive. I fell asleep in about 5 minutes and that's when I heard our tires going over the rumble strips making loud bumps which woke me up. I woke up and looked at my wife and she was fast asleep with her hands slipping off the steering wheel. Our car was slowly drifting to the right, and about half our car was in the median a few feet from going off the freeway down into one of those enbankments. We were going about 80MPH. I slowly corrected the steering wheel and gently nudged her awake. I then immediately had her pull over and she literally has never driven on any of our road trips ever again haha.