It can be tricky to discuss characters in a poem, especially when that poem is not a narrative poem that tells a kind of story. Simply put, a character is a person (or something like a person) in a piece of literature. The speaker in a poem can be considered a character, as it is safest not to assume that the speaker is the poet, generally speaking; the speaker could be the poet, but we ought not to assume this necessarily. When we make this assumption without clear evidence, it can lead us to jump to conclusions about the poem's content and meaning that are not necessarily supported by the poem itself. On the other hand, this assumption—that the speaker is the poet—can distract us and prevent us from drawing correct conclusions and meanings from the poem's language and ideas.

The speaker, this poem's main character—or protagonist, if you will—is driving home by night, and he or she describes the sights of various objects when the car's headlights shine on them. The speaker also discusses the people who are sleeping, as well as what happens to the speaker when he or she tries to go to sleep that night. Strange images push themselves into the speaker's head during that period between wakefulness and sleep, and the speaker has no control over these images or how they affect the speaker's mind.

There are also "people" who are sleeping while all of this is going on. Some of them sleep peacefully, while it seems to require a great deal of work for others to remain asleep. Even those for whom sleep, their sleep is like "training" to hold on to that sleep, and they rest heavily but tentatively. The speaker compares them to the crossing barriers that block cars from passing trains.