There are tracks and passenger rail services around San Francisco’s Embarcadero which are
railway=light_rail, yet “what the passenger rail services are called” (either streetcar/tram or MUNI light_rail, a distinct “thing” in San Francisco, distinct from cable cars, historic streetcars, BART, Caltrain, and the monorail at SFO Airport which are ALSO rail in San Francisco, but Amtrak bypasses The City) varies. In some places (around Pier 1), “light_rail travels over track which might be called streetcar/tram track” (so which do we call it?) and in some places, it’s a bit more convenient in tagging (or is it?) to say that “streetcars/tram travel over light_rail track”? It’s a cluster of examples where “yes, both” is the answer.
Edit: San Francisco even additionally has
route=trolleybus (electric bus, power from overhead lines). A newly-constructed Central Subway is part of MUNI. The high-speed-rail station of the future is under construction. Local transportation jurisdictions talk seriously about another passenger rail tunnel under the Bay. It is amazingly complex, OSM sometimes struggles to keep up with accurate tagging. Los Angeles is another booming rail construction zone (partly to prepare for hosting the upcoming Olympics).
Even talking about it is complicated, but I capture the gist above. If you care to look at the ways, you can, though describing them beyond “passenger
railway=* around Pier 1” gets tedious.
It’s not so that particular
route=light_rail relations are “seriously disharmonious” with PTv2, it’s more like a sour note among a symphony. We haven’t totally ruined anything, but the scheme could use more harmony, because of the complexity of how we “tag tracks,” and seem to “straightjacket services” into niches which aren’t really true, or are quite grey / fuzzy / flexible and which certainly wander around a great amount between jurisdictions and regions. Highly multiple-rail-service areas (like Downtown San Francisco, there are many others in dense, urban centers) especially exacerbate the breakdown along the edges of this. It’s fuzzy and can use sharpening up, but it isn’t wholly broken. “Minor ambiguities,” let’s agree, which are hard to disambiguate.
I’ll give us around a solid B, maybe B- in places, maybe B+ in other places. Some really polished areas creep into A- or even A (not A+) territory, but we need better tagging and schemes like PTv2 (or PTv2+) which improve things. Rail is really rich. We’re not done, we’re good, very good in places, we can get better.