I think deer react before they think, like roaches. Quoted from first google hit...
Quote:
A scientific advisory panel from the World Society for the Protection of Animals states, after extensive review, that there is no known data "that shows that such devices can actually stop an animal crossing the road, which is the main purpose of the device."
Even if the devices were effective, they would soon become clogged with insects and dirt (since they are mounted on the front of the vehicle) and would stop working.
The state police in Ohio, after months of testing, found no significant decrease in patrol car/deer accidents after the warning devices were installed. In fact, more accidents were reported by the officers after the whistles were installed than before for the same period of time and stretches of highway. Tests conducted in Utah, Georgia and Wisconsin also concluded that deer whistles don't work
