What exactly is a "trip" I think comparing per mile is much better than per trip. I take make two dozen airline trips a year but I can do that many car trips in

What exactly is a "trip" I think comparing per mile is much better than per trip. I take make two dozen airline trips a year but I can do that many car trips in a week. On the other hand most of my car trips are on the order of a mile or two as compared to several thousand in a plane.