a) In a city there is not much space to build two small streets for buses/trams, and you don't really find this in a real city...
b) I guess you mean a stop for each bus/line - I thought about this, but if bus 1 arrives first at its stop (its stop being the second), bus 2 would have to wait for the first one to leave so it could stop at its stop (the first stop) + to put the stops where I want, the road would have to be sectioned in two and that would make things a bit difficult...
I just wanted to know if I could solve this with a script. Anyway, thanks for your answer.