Berlin moves it

Yes, we like to move it. Investment in infrastructure follows a long-term economic rationale. In urban areas space is a scarce and, therefore, an expensive resource. In order to use the current space for mobility more efficiently, the use of a longer tram or train is an effective way to increase capacities. Rather than to increase the frequency, which is no longer possible without safety risks, a longer vehicle allows to bring more, and more diverse, passengers on board (kinderwagen and wheelchairs included).
It is a long-term objective to make urban areas liveable for all ages. Tramways which allow a low or, better, no barrier to entry is a necessary condition in this respect. The new “Urbanliner” in Berlin (image below) offers such essentials of access and urban mobility. A single tram is 50m long with 88 seats and 215 standing persons in larger corridors. 300 tram passengers can be compared to about 12 average length cars with at best 15-20 passengers.
A consensus of “how best to move it” in cities pays off in the long-term. Planning has to start about a decade before delivery and needs to survive political cycles going back and forth.