Wildlife on roadways
exacts a terrible cost. If
the animal is large
enough, it can kill the
occupants of the car
that hit it, and even
smaller creatures can
do plenty of financial
damage. In addition, it was
estimated that a million
animals are killed on U.S.
roads every day.
Sometimes there are
ways to persuade
animals to spend their
lives on one side of a
highway, but often
there are good reasons
for them to cross.
Source: http://www.iflscience.com/technology/art-building-animal-bridges#overlay-context=