With no bumper on a Smart car where should Deer Whistles be placed?

Answer 1

They'll do approximately as much good in the glove compartment, or better yet still in the package in the store, as anywhere else.

Every study that's ever been done on these devices has concluded that they have no measurable effect. In fact, state police in several states have noted that after installing deer whistles on patrol cars, the number of deer/vehicle incidents actually increased from those over a similar period the year before the whistles were installed (this is probably coincidence and not a causal relationship).

Occasionally vendors of these devices will claim that studies in Europe have proved they work, but if you actually read the studies they cite, the ultimate conclusions are, again, that the whistles do nothing. Save your money.