The tension that Hopper achieves by having three separate groupings of people , each involved in their own worlds and "isolated"from each other works for me.
Hopper was always sensitive to his subjects and their uniqueness and separation from each other.This is conveyed because the scene is like a"stake out" by yet another observer.
He did a coupl,e of these "stake out " scenes in the early 1940's. (Nighthawks, Drug STore, Night Windows,).
To me they state that "were all in this separately" . That sorta embodies an existentialist worldview