The most common species turned into museums with ornithological
collections are often Great Horned Owls, Barn Owls (in the south),
Barred Owls and Red-tailed Hawks.  This is in part due to their size -
people notice them when they are dead along the road.  It is also due to
the fact that they hunt for mice along roadsides and get hit by
vehicles.  So there are regular losses in these species to vehicular
collisions, but there seem to be plenty of Red-tailed Hawks and Great
Horned Owls around in most places, so a substantial proportion of their
population appears to learn how to hunt safely.  

Snowy Owls that come to our region in winter are Arctic-raised birds.
They probably have no prior experience with vehicles. It is often
suggested that Snowy Owls only leave their Arctic habitats when low food
levels force them out, and it is usually subordinate birds (often
juvenile males) that are forced.  The result is that the birds that get
here are very inexperienced.  The bulk of the Snowy Owl population
maintains itself way to our north, and so the tendency to be wary of
vehicles never spreads through the population.  From an evolutionary
standpoint, one might imagine that such a behavior would spread if
substantial numbers of Snowy Owls successfully survive the winter here
and return to breed. But most of the successful birds are the ones that
never come here to begin with.  The few returning Snowy Owls that DO
winter in our area do not make up the bulk of the breeders, so their
traits do not necessarily spread. At least, that would be consistent
with the basic theory.