In some german citys, streetcar tracks are separated from the carways, at least in the city centers - separated in a way that a car gets damaged if they try to violate the separation.

Taking into account that a subway is so much more expensive to build than streetcar tracks, that driving in bright light outside is more enjoyable than driving underground and probably, that we want cars to stay out of the cities as much as possible, streetcars are great, imho. More comfortable than busses for sure.