That is exactly what I do in the car. My mother has says I've done it for as long as she can remember.I love to stare out of car windows when someone else is driving, feeling at-one-with passing scenery like trees and houses, or imagining what kind of horrors might inhabit the passing woods or decrepit, old buildings; or imagining myself swimming in a passing river like a fish; or imagining strange orbs or aircraft hovering above passing skyscrapers; or wondering to myself who drew that passing graffiti and what message they were trying to convey with it. Internally I get annoyed if the other person in the car gets "bored" and tries to make conversation, usually by making some inane joke or something; but I try to be nice and pay attention and respond to what they're saying.
I cannot prevent my daydreaming either. What is worse is that I can be so in it that after a while I notice how people around me are giving me strange looks and that is when I know my facial expressions are making me seem like I do not fit in with the same environment that they are in.The problem I have with daydreaming is that I barley can prevent it from happening, and when I start I often end up losing control as if I were in a dream at night, and I become oblivious of myself, my surrounding and lose time. Coming to think of it, it's almost only in daydream mode where I can think efficiently in words, otherwise my natural mode is to "improvise" -- speak/write in order to really be able to think things through.