This is essentially a game with no winning conditions. When you start playing, you know that your system will come to a crashing halt at some time, no matter what you do. I think there is enough randomness in the game that disasters or breakdowns aren't really needed.
This game isn't a simulation and really isn't supposed to be realistic. If the developers wanted to turn this into a full subway simulation, I would be all for it, but there would be an awful lot of work involved to do that. As it is now, it is just a nice little time killer where each game lasts almost long enough.