Screw them cars and the traffic jams they create. Lower the speed of them and they won’t appear any more. I only see a few now in my games and my bus stops and train stations have passengers again.
This guy lowered the speed of the cars to 50 – http://www.train-fever.com/forums/topic/mod-traffic-decongestion/ – which works but I made mine go 2 mph but changed to 10 mph because sometimes a bus will get stuck behind one of the few that shows up.