Yep, they work but you must be going 15 MPH or faster. I've used them on our trucks and cars and even on my Semi tractor when I was working..
There is a better deer whistle that works very well moving or setting still. It will keep the deer off your vehicle. It can be seen here and it's worth every cent you pay for it. The Hornet Deer Whistle - Electronic Deer Avoidance System
It's electric with one wire hooked to the battery and one ground wire with a on and off toggle switch attached to your dash. Check it out.. Much better then the little plastic ones that stick on.
2011 Cedar Creek 36B2 ordered with outside kitchen removed and a nice big wardrobe in it's place.
Pulled with a 2011 F-250 Super Duty 6.7 Diesel Crew Cab and 8' box with a Hensley BD-3 Trailer Saver. F R O G members.