We drive because we want to be somewhere else. We can get there soonest by going straight, and fast. But other folk also want to get "somewhere else", at the same time. Our paths will likely cross.
So we need rules about who should "give way" : signs and markings. So far, so good. If there's lots of us, we may need to slow down, or even stop. So we have routines, for gently changing speed and direction.
If there's LOADS of us, we use mirrors to assess how our decisions affect others close by. But there's always an easy hierarchy to our actions.