When my husband and I travel, we can go for twelve hours without having any conversation beyond “Where do you want to eat?” and “Do you have to pee?” He drives and listens to a book. I read a book and handle kid problems. That being said, should one of us say something outside of our usual conversation, it will probably be the exact thing the other is thinking about.
If I had to chose people to go along, (and I’m assuming these people would converse) I would want people who can tell good stories. (I’m also assuming this a long and otherwise boring car ride, but it is in a comfortable car because my massage therapist cried after my last road trip.)
Another person I might chose would be one of my Classics professors from college. One of them had a voice for radio and could make Latin conjugation sound interesting. He also made Greek and Roman mythology absolutely fascinating. If we were touring the Mediterranean coast, he would be the perfect travel companion. Our college does trips to these areas, but probably by the time I can afford to go this professor will no longer be traveling.
So I’m probably not a very exciting travel companion, but I’m a great listener.