Highways and interstates (and some minor roads) comprise the setting of this novel. (The characters do stop at a few houses, but these function as pauses in their journey.) The characters spend so much time on the road – and McCarthy describes the road so well – that it hovers over the novel as a major image. The road is a desolate, transient thing, full of danger (the "bloodcults"). In fact, it's probably useful to think of the road as both an actual, physical setting and and a mental state.
Check out our discussion of "What's Up with the Title?" for lots more of our thoughts on roads.