If I'm driving on my own - have some music playing, fairly loud. And pay attention to the road and the other drivers. Queen is a particular favourite, if only because their Greatest Hits 2 is long enough to sustain a long-ish drive before stopping at services. The same goes for the Pet Shop Boys' Further Listening CDs that accompanied the re-releases of their studio albums back in 2001. Or a nice '80s compilation.
If Sarah's in the car with me, the music tends to be less loud ('cos she doesn't like it loud), and if Sarah's driving, the music tends to be non-existent. Heck, sometimes we have a conversation. :o)