I know this may be a totally foreign concept to people living in the valley, but a driverless car isn't very interesting to people who can just walk onto a regular, punctual bus or subway service on near every corner.
One can also imagine a massive drawback: the continuation of sedentary lifestyle status quo and all of its associated ills.
But hey, who wants to walk 10 minutes to transit, maybe you can take the driverless car to the gym.
Driverless vehicles have the potential to transform transportation, full stop. This obviously includes public transit (I highly doubt that a driverless bus is much of a technological leap from driverless cars). Whatever benefits public transit provides are included in the changes that driverless vehicles will bring (unless, as it seems, your only in support of inefficient public transit?).
I have no idea where the car accidents or pollution sentence came from. I'm "rooting" for less cars, not the least because it will reduce pollution, and live my life accordingly. I try to minimize the disease in my life by minimizing my car use - automated or otherwise - rather than addressing the symptoms using a new wundertechnology. I don't control the number of car accidents because I can't control the choices others make.