There's no way self-driving cars will reduce traffic volume. If anything, it will increase since not only you don't need to be able to drive in order to travel

There's no way self-driving cars will reduce traffic volume. If anything, it will increase since not only you don't need to be able to drive in order to travel in a self-driving car, the car might be completely empty and driving on its own for some sort of reason. And of course people who currently drive a car will still be driving a car (which might be self-driving or not).