well .. by complexity I mean mostly:
– Multiple trains using same route without getting stucked
– Set different platforms on a station for passenger / goods trains ..
– Add / remove wagons automaticly on station ..
– Going from point A to point B twice …
– Set waiting period …. wait until 100% full .. or wait until 80% full … or wait 2min then go… ect..
– Set priority to some trains .. for example a train waits to get fully loaded on some station .. but if some other train with priority comes along .. that waiting train should leave.
in short … I hope that I will be able to do a lot more than I could in Open TTD