Since these cars are autonomous, they could simply be programmed not to do that. I'm sure there would be endless complaints about intrusive regulation, but there would probably also be applause as every driverless car cruising in traffic was subjected to street justice.

Seems like an easy problem to fix, doesn't it? I mean simply ticket vehicles that are driving around past a certain point more than once, especially if there is no one in the car. Or many other possible solutions.

I think that the law could easily require a private self driving car to have a passenger in order to even move. In fact, I think it was pretty much the way most people envisioned such cars.
However, it's nice of researchers to come up with interesting ideas, and it certainly allows further development. In the future, perhaps special car parks in cheaper areas could be made for self driving cars, so they could drop their owners and then park some way away and wait for them.

IMHO, if any auto-car company tried to add a "Tour Around" option (to not pay high parking fees), all big city governments would immediately have a "big problem" against that! :-)
(& w/o such option provided, how a driver can really make the car just tour around, exactly? Because the car would always expect a place to go, before start driving!)

This is exactly what I argued at Treehugger and those wanting to make everyone use autonomous cars and I told him it would increase traffic and he said no way it will decrease traffic. I know for a fact it will increase greatly traffic because those cars just drive all over the place and never park. But Treehuggers have no logic just emotions to curb people they want to kill off billions of us to save the Earth. That's their way of thinking and it's bull because they don't know half of what their talking about.

Sounds suspiciously like a new tax to me.

I can understand their motivation for the research but it's far enough away that it's really anyone's guess how it will pan out. For starters if cars are automated enough to be able to do this the only reason for using your own car instead of a taxi/uber is if your stuff is in the car and you don't want to carry it. This should mean many people won't have an individual need to park freeing up parking for people that do. Reduced parking demand should reduce parking costs helping to alleviate the problem. Something else not accounted for is the concept of remote parking lots. Walking distance is high because all of the required parking. If your car could drop you off and drive to a remote parking lot in a less premium space we would have more walk-able cities that wouldn't have the problem of expensive parking in high demand areas or cars circling the city. It's hard to study the impact of something like this without crystal balls and palm readings. Despite mostly working models of this technology already existing I still think it will be a long while before we see driver-less cars on regular streets.

One thing I've learned over the years is that the doom prognosticators are more often wrong than right. Like the rest of the problems that have been brought forward regarding driver-less vehicles, this is just a transition issue.
What the author fails to take into account is a probable reduction in owned vehicles. Why will people go through the expense of owning a car with all the extra costs (payments, insurance, license, maintenance etc.)? In a few years people will be able to order up a vehicle the same way a person can order up an Uber today. That driver-less rental will take you to your appointment and when you are done you can order up another vehicle to take you home. The only costs to you being the rental fee for the trips.
In the end, when there are no more drivers and the amount of vehicles on the road will be less, the flow will be fine.

I argued this consistently in online forums but those favoring autonomous EVs are never logical...jist emotional. Autonomous cars will increase traffic because parking costs more its a simple economic reason they will follow. But those wanting to sell and rent cars deny that will happen and their flat assed wrong

Another solution would be to add more incentives to share self-driving cars instead of owning them. After all, riders don't need to own an Uber or a Lyft car right now, and riders don't need to pay to park them anywhere because they don't park.