"And perhaps beyond the shrouded swells another man did walk with another child on the dead gray sands. slept but a sea apart on another beach among the bitter ashes of the world or stood in their rags lost to the same indifferent sun." (Page 219)
What does the quote mean from The Road?
One of the constant themes of the story is that of complete isolation. Not only are the man and his child alone in that they rarely see other humans, they also seem to be the only ones left who have a sense of humanity and decency. The horrific scenes they come across and the dangers they face because of the utter degradation of humanity after the nuclear holocaust are a constant and powerful motif in the novel.
This particular idea, that of the possibility of there being someone else like them, is held up to show that they still act out of an irrational sense of possibility, that just maybe there is a kind of redemption out there and maybe others are looking for the same but they face insurmountable obstacles both on their own paths and in finding others like them.
This passage evokes that hope in an image and while it acknowledges the obstacles they face, it keeps open that possibility.