What kind of display did you use for the tram-stop times? I wanted to do something similar but worked out that the cost to update the display every minute was too much in terms of battery life even with an epaper display. Also, it was too inconvenient / ugly to use mains power.
I do have a couple of epaper devices, and they would be ideal but for their terribly slow update-time. I like the clock showing Time & Date (or Time & Temperature), and having epaper update every second just isn't possible. Even if it were then I suspect updating so frequently would negate the potential power-saving of using epaper in the first place.
I do have a nice epaper device for showing weather & weather-forecasts, that works on batteries and updates every 20 minutes. But for trams I update departures every 2 minutes.
Not OP but did a similar project, the display method I used was simply to use 9 led lined up, each representing a stop before mine, to show the current position of the tram.
