Insurance rates for human drivers could easily skyrocket, relative to the rates for robot drivers, while declining in absolute terms, because the overall cost of providing insurance at all would decrease.
You can see this effect today, with motorcycle insurance. Motorcycle riding is far, far riskier than car driving, and it is a largely voluntary activity. You might expect that motorcycle insurance would be spectacularly expensive relative to car insurance, but the opposite is true: motorcycle insurance is so cheap I don't even think about it, so cheap I pay for a year at a time - under a hundred bucks, I'm not sure how much exactly.
Why is motorcycle insurance so cheap? Because providing motorcycle insurance is cheap. Insurers charge whatever they have to charge in order to make a profit over whatever they have to pay out, and motorcycle insurers don't have to pay out very much or very often.
Step into a hypothetical future, where level-5 auto-driving is everywhere, and collisions overall have dropped by 100x. The cost of providing car insurance will necessarily also have dropped by 100x - perhaps even more, if the types of collisions which remain are less damaging. If most vehicles are driven by cautious, predictable robots, capable of maneuvering intelligently to avoid other vehicles, then even human drivers would get into far fewer crashes than they do today. One can imagine a drunk driver speeding and swerving down a highway but failing to hit anyone, because all the robot cars are casually and gracefully weaving out of its way.
What can we expect, then, for people who still want to drive their own cars? Yes, likely they will pay a higher insurance premium for that privilege: but so what? With collisions overall being so rare, and car insurance overall being so cheap, insurance at a 10x or even a 100x markup compared to robot driving is still likely to cost less in absolute terms than car insurance does today. What's the big deal?
People will continue to drive manually for fun, or because they like old cars, or because they live on a farm, or in the woods, or because they like to go camping out in the woods, or whatever. Manual driving is simply not going to disappear overnight like this article is suggesting. Instead, I think there will be a slow, steady drift toward automation, much like we've seen with the gradual transition from manual to automatic transmissions.
Motorcycle riding won't be automated any time soon, that's for sure. What would be the point? So we'll have humans piloting vehicles on the highways for a long time to come, in some form or another.