@bythelee ” The game might let them use alternative means for each journey, and not require both to use the same mode of transport. I suspect so, because I rarely see even usage of the contra-rotating lines. One is often as little as 1/2 or 2/3 of the other.”
There is an answer. On the train unload you get about 100 people looking for a bus in the target city. About 1/2 do not find a bus in the 20 minute limit. So they disappear. Therefore they do not travel back.
Similar issue “the station overload”, has the supply chain factory->train->truck->customer. Train overload the truck station so the goods puff to void. Mentioned dozen times to the devs, no fix or even answer.
