I'd like to add something about the meaning of that scene. As far as i know, science argues that dogs/animals don't commit suicide, not consciously at least. But what the scene is trying to say, imo, is that the small spaces we live in (and the lives we live) are so absurd, even a dog would commit suicide. Also, the obvious fact that bypassers were more interested in the dead dog and the passed out lady instead of the man that got hit by a car (who needed the help the most) - as a picture of today's society.
Hopefully this makes sense. It's 6 am here, so i'm not too sure.