Just like the ideas and emotions in this poem are more complicated than what appears on the surface, the sound of this poem is more complicated than it appears. Dunn uses a lot of subtle sonic word play to create specific effects in this poem.
Ready to dive in? Good—let's get specific. Look at the first stanza. Dunn uses a lot of different A sounds. For example, listen to the short A sound in "after," "asked," and "had." This is called assonance. But how do we know that's not just a coincidence? It's like this: the repeated sounds in the line create a rhythmic feel as if the line is in motion. It's like the sound is rolling across the page just like wheels roll along the road, right? Let's try another line and see if it's still there.
Line 2 gives us "a," "sacred," and "place." Those are all long A sounds, like the kind you get on a report card. Dunn is using assonance for the poem's benefit. It binds the words together and reiterates the idea of motion and driving, which is central to the poem. In this way, Dunn is linking the literal meaning of the words with their sounds. Check out the rest of the poem and look for other moments of assonance that keep the wheels rolling.
We also want to mention Dunn's subtle use of repetition here. Repeating words isn't really rhyme, because the speaker is using the exact same word. However, repetition does contribute to the circular "motion of a wheel spinning" idea, and propels the poem forward by going back to something it said earlier. Let's inspect those wheels...
Lines 5, 10, 11, and 15 all have "car" in them. Captain Obvious reporting for duty here: "car" must be important to the poem, right? Thematically, yes, the car is important, but because it is repeated in the poem it physically moves as if the word "car" is literally driving through to the end of the poem. Repeating the word draws the reader's attention back to it and also visually moves the word. Sonically, the repetition of the word creates a cycling motion, like the word spinning forward and popping up in different lines. The word "car" is moving though the poem just like a real-life car might. Again, Dunn is a highly skilled sound engineer who is using these sonic echoes to subtly underscore his content.