If you see a horse and rider on the road where you are driving, you should:

Any time you encounter an animal on the roadway, drive slowly to keep from frightening it. When driving near a horse and its rider, you should slow down, move away from the horse, and avoid using your horn or accelerating in a manner that may startle the animal. Animals can be unpredictable and you should do everything you can to keep them from running into your path.