I dealt with this issue in a flippant way earlier, theorizing that dogs were committing suicide. Now I have a more serious theory, based in canine phenomenology. Basically, dogs are unaware of automobiles' existence. The dog's phenomenal world is constructed out of powerful smelling, tasting, and hearing sensations. Though we think of some dogs as "sight hounds", visual perception is less important by far than smelling. What a dog smells is cued by genetic inheritance (all the biochemical sensing involved in smelling other dogs, smelling prey, smelling predators, smelling food) and experience. Experience is framed by the genetically loaded sensory perception. I don't know of any empirical experimentation on dog's perception of automobiles, but I would guess that to the extent that a dog experiences an automobile as an object of perception, it is the smelling cues associated with aromas of family members in the automobile, of the food they carry into the car, and some memory associations connecting the car to pleasant experiences, such as visits to locales where others dogs are present. The auto itself as a bundle of smells--gasoline, grease, plastics, etc.--is probably not even perceived by the dog. When the dog is interested in crossing a street--perhaps to investigate an aroma located on the other side of the street--with cars passing along the street, the dog is not even aware that the cars are there. For the dog, the street is empty and poses no threat (or pleasure or reward). So it bounds into the street fixated, without caution, on the pleasure awaiting it on the other side. Cars per se are not valuated in the dog's experience. They do not benefit from the tragic consequences of being hit by a car, because generally they do not live to have learned from it.