>>2021370Other than the mentioned things above like comfort or capacity, there are plenty of cities in Europe that run long trams that approach metro line capacity and ridership. There are also cities where certain lines have grade-separated sectors or where the tram works are a pre-metro. There are also areas where there are just not enough room for buses.
In case of maintenance or an accident there is a bus replacement and generally it is a pain in the ass compared to regularly scheduled trams.
