I am playing (1st time) a map with huge cities. Right now, I'm connecting a city of 150k pop. with bus and tram lines (and later I'll build underground trains too). Since I've only recently opened up many new lines, it is obviously far from optimized, and I have some very full stops.
However, clicking on the full stop gives me a list that:
147 passengers > via Lancaster axis stop
45 passengers > via Lancaster external stop
34 passengers > Lancaster inner stop
33 passengers > Lancaster central stop
etc.
... and with 50+ stops, I find myself at the first level of hell to figure out what line is not running optimally. I don't know where those stops are, and I don't know which line needs more capacity (if any, maybe the busstop is just too small).
So, now I started to rename all of them systematically. I'm gonna call them by the lines that serve the stops, so a stop could be called 'Lancaster T1a B3d', meaning it's in Lancaster, on Tramline 1 and also on Busline 3. And following the tram and buslines, the 3rd letter in each code just goes up alphabetically, so you know how far it is along the line. So far, the alphabet proved longer than my lines.
The benefit is that you can see in one glance that half the people crowding the stop will take the tram 1, and the trams have enough capacity... so, no worries.
It seems to work, but it's tedious to rename everything. Maybe there's an easier way to remember (or, I almost don't dare to ask after playing only a few weeks - maybe some brilliant developers would want to automate this - so the game just shows which lines we're dealing with - maybe so you can toggle it on/off?)...

What do you guys do now to keep track of what's what in a large passenger network with many lines with many intersections?
p.s. Unrelated, but not worth its own thread: When you get a noise like a car engine that wont' start on a cold morning - what is that about?