I figured this could be a little controversial but would end up with good results. Why not bring the passengers to life, they do after all play a key role in the sim. The idea is to have them complain, cheer, thank you, get angry, make comments of all sorts. etc..... Like for example you walk on a platform and you bump into a woman, she would generally if in a good mood say oh pardon me, or hey you bumped into me, be more careful. Some people might be anxious about late service to get to work on time or meet friends. You can even say hello how are you doing today, reply back or not reply back. And the fun stuff, whilst on the train, nobody could say anything or they could be chatter boxes. If you drive rough they could make comments on it. So all that sounds good but it's probably not easy. Firstly the 1st step is to give them basic speech based on the country and time period at present. Very basic interaction, just basic hello, thank you or a hi. Obviously lots of opportunity for bugs to creep in as well.
