I looked into one of these in the past. http://www.sav-a-life.com/Deeralert_brch.htm but you have to be going at least 30 mph for it to work. I only hit that speed on a downhill. If it is dark and I am in the area where I see the most deer I will start whistling and snorting like them. It may sound funny, but I haven't had anymore close encounters with them.