According to this post on the Freakonomics blog, when men and women ride in the car together, the man is much more likely to drive, even in households that consider themselves to be feminist. It's not clear why this is. Do men prefer to drive? Do women prefer to ride? Are men more likely to own the car?

Perhaps it is because women are worse drivers than men? Surprise! Stereotypes to the contrary, women are actually safer drivers than men.  This is especially true among young adults.  Don't believe it? Why do you think insurance premiums are higher for men? In fact, one study found that more testosterone leads to more bad driving in men: men with longer ring fingers (an indicator of more exposure to testosterone in the womb) had more traffic violations. 

So guys, do your part for feminism and lower health care costs: let her drive half the time! Plus, then you can play with the on-board computer.  Because everybody knows women are worse with technology than men...