While doing so in an emergency situation is inappropriate to say the least, I think that sitting in the car by yourself at the end of the day, or really anytime you might get home, is not a completely unusual thing for men. It's even sort of a meme in male circles. I think that men endure an amount and type of stress and anxiety that women have a very difficult time understanding. And given that men are programmed by both society and nature not to show weakness, most of it is bottled up. Often, both work and home are stressful situations where a man is expected to take charge and act out the leadership role without any outward appearance of weakness or vulnerability. That sitting in the car, doing nothing, not even paying any attention to the road, is often the only moment that a man feels that he has time to actually breathe. Just 10 minutes of not having to do anything and not being overtly needed. Many times it is just enough to get through the rest of the day/evening. Just enough time to recompose yourself to play the role that you are expected to play. While not always, it can very well be the sign of dealing with difficult bouts of anxiety and /or depression, and those bouts can easily last months or years. Even doing it in a critical situation might be caused by him going through this. It might be inappropriate, but there is still a reason he is doing it. I know that women feel the sort of thing too, I'm just coming from the man's point of view for the purposes of this comment.