Heh, I was just reading last night how on the Moscow metro they have a male voice on in-bound/clockwise trains and a female voice on out-bound/counter-clockwise. Not sure where they switch over, given that their lines are generally through-city (like our trams), but I guess the main thing is you notice pretty quickly if you get on the wrong train at the platform...

Pre-recorded voices do have the advantage that they are recorded by professional voice actors in a studio, rather than random drivers in the rather noisy environment of a train. Annoying, artificial cheerfulness is a problem, but that's a choice, not a basic part of the system. You can use "dear passengers, please" or drop it at will.

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