Deer whistles don't work. If anything, it means the deer stops in the middle of the road to wonder what the hell that stupid whistling noise is.
What does work is not outdriving your vision.
The other thing that works is driving a lifted pickup with a big bumper. If I were to hit an elk, I would probably lose my radiator, but I wouldn't hurt my truck. My biggest problem would be wondering how to get the elk into the back of my truck.