driverless cars and human productivity

Driverless cars are likely to soon become reality, as California has recently become the third state to explicitly allow non-human drivers on the road. Most discussion about the impact of driverless cars has centered around the reduction of harm: automated driving systems won't get distracted, careless, or drunk, most likely reducing the number of accidents involving cars. While it's definitely one of the strongest draws of self-driving cars, I've recently been thinking that the really big rewards for humanity will come from the aggregate increase in human productivity that will result from letting people think less about driving.
After you've been driving for a few years, navigating roads and traffic becomes pretty routine -- and falls short of being a fun activity. The act of driving doesn't engage your entire brain, and can even get painfully dull, particularly during longer highway journeys or when stuck in slow-moving traffic. It's possible to do passive activities like listen to music or the radio, talk with one of your passengers, or daydream with your spare cognitive capacity.
But when trying to actively multitask, or upon encountering some challenging road situation, your full attention is again needed at the wheel. Ultimately driving takes up just enough of your brain that it's not fully automatic (like walking), yet isn't intrinsically interesting enough to keep you occupied.
People spend a tremendous amount of time driving, and so automating the process and allowing drivers to perform active tasks like reading books, learning from videos, videoconferencing with coworkers, or working on email, writing, or even art will unlock an enormous number of human hours currently spent in the driver's seat. Indeed, the National Center for Transit Research estimates that Americans alone spend over 3.1 billion minutes a day commuting, and with 73% percent of city dwellers commuting by car, there is a massive amount of aggregate human experience being wasted in the monotonous existence of the daily commute.
I've always appreciated taking trains or buses because of the fact that you can read or use a phone at the same time, but if cars are developed into a kind of mini mobile offices, this side effect of commuting will just be even more common. Secondary driver's tasks, such as taking the time to drive to gas stations to refuel, or dropping a car off at the repair shop, might also away if people didn't have to drive, freeing up yet more time.
Of course, there are always tradeoffs. The first cars will likely be quite expensive, and so these benefits are likely to be realized by the wealthy, increasing the gap between rich and poor. Driverless cars might also encourage people to live further away from city centers, increasing congestion and furthering the sprawl of our cities. And of course, those who do drive professionally will have to find new work, although there will be plenty of jobs supporting the maintenance of a new fleet of vehicles.
It will be fascinating to see how this technology ends impacting affecting society, since it has the potential to so drastically shape the way in which we spend our time.