many cities have wide highways, cutting through dense areas, where you would want a tram.

lol no, that’s how it works in canada and it’s shit.
This is precisely the place where light rail makes sense: it’s most of the benefits of heavy rail but way cheaper, so you can build more of it and run more vehicles, and operate like a metro in the suburbs but as a tram in the downtown.

Basically what you want is Portland but with 10x as many lines.