There are so many ways to describe how wrongheaded this is that I don't even know where to start.
The idea that less efficient transportation is beneficial because it would require people to be more active is absolutely insane. By that logic, we'd be better off with no transportation other than walking; I find it hard to believe that everyone would be better off if they were constrained to working somewhere within a few miles of them (or alternatively, required to spend half their day just getting to work). Rooting for a higher level of car accidents, pollution (the number of cars needed could easily be cut by as much as half), and congestion in order to force people to walk is ridiculous. Throw in the fact that sedentary lifestyles/obesity are pretty strongly correlated with lower income and education level (ignorance of health/nutrition issues, lack of time due to heavy work schedules, there are different reason for different people in this situation), and the economic benefits alone of a significantly more efficient transportation system would likely cancel out whatever possible increase in sedentary living it may cause.
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?).
What kind of efficiency are you discussing? What are you comparing? Roaming driverless taxis are not more energy efficient and they are not more space efficient than transit. Being an improvement on human-driven cars is not a particularly difficult achievement.
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.
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?).