I take it you don't ride buses. They are often completely full in rush hour, including people standing. Meanwhile, most cars have only one person in it. Maybe

I take it you don't ride buses. They are often completely full in rush hour, including people standing. Meanwhile, most cars have only one person in it. Maybe an average of 1.5. You could have a carpool with 4 people in it, but I think that's rare compared to single passenger vehicles.