It's a disappointment this writer is covering this topic.
Self-driving cars can be great because of the shear impact on utility for vehicles and safety implications.
I'm quite excited about the advent of self-driving cars and the underling operating systems that will make them amazing for humans.
I do believe there is room for both types of driving. It's possible our freeways will be segmented such that automated cars can go in certain lanes (perhaps even barrier protected) while the remaining traffic stays in other lanes / roads.
Traffic, or more specifically congestion, is primarily caused by excess cars on any edge (road) in which it simply takes N+1 cars to cause. Inconsistent driving patterns cause effective waves of inconsistency down the pipe exacerbating the situation (stop and go traffic actually makes congestion even worse).
Thinking about the overall network at a higher level makes all of this even more exciting. Consider the scenario in which N cars are on an edge with capacity N. If your car was about to enter the road you would basically contribute to traffic. This cost, C, is then felt across N+1 (don't forget to include yourself!) people at a minimum which is C*(N+1) minutes of human time that is lost.
If our cars, and ourselves, were better informed you might take an alternate and sub-optimal route that taxes you an extra T minutes but the overall network of time is optimized. Perhaps you'll even get a reward for it. And perhaps the reward is simply allowing all the people currently on the road a faster commute home so they can be with their loved ones.
Beyond that, as people have mentioned here already, the faster we can go and caravanning (which can be done safely by allowing cars to attach to one another in train format) improves overall throughput (and make traffic less likely).
Finally if we think about traffic, it's really just load and it needs to be distributed better across all possible routes and time. We have commute hours, but one thing to think about is that with a self-driving car I can leave to LA at 12AM and get there at 6AM while sleeping in the back of the car.
Self-driving cars will increase utility on vehicles, but also on time for travel routes ideally. This will spread the load (since humans generally have some biological clock they operate by) to utilize the 24 hours a day we have a little bit better.
And if your car can't speed I guess we should invest in really good alarm clocks and reminders :)