Curb lane seems to be the preferred location for streetcar tracks and street-running light rail tracks now, rather than the traditional (in SF) middle of the street. It affects parking drastically, but is better from an access standpoint and effect on landscaping. Side of the street is used in Portland, I think in parts of the SeaTac area streetcar lines, in Sacramento light rail, among others. At least it's not on the sidewalk like in San Jose, or removing lanes from the street as in Phoenix's most recent proposals (which have led to a campaign by the Koch Bros. organization to eliminate funding for PHX light rail construction, if not the entire system) and SF on Judah St.