Trains are for long distances. Trams are for pure urban areas. Metros are for connecting cities within a metropolitan group. All those function within a well planned urban structure, not the suburbs, or exurbs. Cars are the most efficient. That is why most Americans own a car. Without a car, you are asking for long walking distances, and long bike rides. City transit systems don’t work in the US, because too many criminals are out in public, and people like their own space. Americans like their own space. Again, you are talking about a specific type of living, that most Americans don’t really gravitate to. Americans want a large house in a safe neighborhood in the suburbs, or live in the exurbs.