What kind of car does your protagonist drive? Use the make, style, and color to further define his or her personality. James Bond drove an Aston Martin, not a Volkswagon bus. Think about it.
Think about your friends and what they drive. What does it say about them as a person? Do they lease a new car every year or so or, conversely, drive one that’s over a decade old? Is it in good condition or beat up? Is it clean inside or littered up with fast food containers? What color is it? They say that red cars are targeted most often by police. Why do you think that’s true? If you’ve had a variety of different cars throughout your life, how did you feel driving each one? Was it simply a means to get from point A to point B, or did you feel omnipotent, or perhaps even vulnerable in it? I sure felt differently driving a Porsche than an aging Suburban.
One example from the TV show “The Big Bang Theory” is how Penny’s “check engine” light was on. What did that tell you about Penny? What about Sheldon, who didn’t drive at all (at least for the most part) and had his friends chauffeur him around? What about the Ferrari in “Ferris Buhler’s Day Off”?
You can tell readers a lot about your characters in so many ways. Their favored mode of transportation is definitely one of them. Even if you write historical fiction, horses and carriages can be used in a similar manner. Science fiction, likewise. Think of Luke’s land-speeder in the original Star Wars.