Based on the fact that cars are not linked together like a train. Cars can go different routes from one another and can go to different destinations. This spreads them out more over them all being in the same place.
So some people on the bus in front of you would drive cars on other streets, and some people on buses on other streets will drive cars on your street; there's no reason your street will have a net benefit.
That's especially true because there will be far more cars on the road.
