The largest tram system in the world looks a bit sad, my random german city with 1/10 the population of Melbourne has 30 Mio. more riders annually on its trams.

They really need more interconnections and maybe some ring routes.

While a plasma is far from an ideal gas:

pV=nRT

p is the pressure, T the temperature, when you increase the pressure while keeping everything else the same, you increase the temperature aswell. The density here is the colloquial term for pressure.