No, it won't be efficient. People here simply are not thinking realistically.
I want to go out to shop. Right now, I get out in my car, drive for twenty minutes to the mall, and leave when I want to do so. My kid is with me, but on the way back he gets sick, so I have to cut short my drive and head back home. he throws up in the car. I clean it when I get home, and go back out to the store five minutes away by car to pick up some medicine for him as my wife watches him.
HN "solution."
I page a car. It takes maybe ten to fifteen minutes to drive to me from the last passenger, since it only is designed to head back to dispatch every so often. The car reeks of weed, because why not light up a bud? It's not like they can arrest you or anything. I punch in a complaint on the app.
We get to the mall. I shop, and summon a car. This time it takes a little less, maybe five to ten minutes, because the mall is closer to dispatch or a place where a lot of cars get dumped off. I program my next shopping route. My kid gets sick mid-ride though.
I have to hit the emergency button, and reroute back to my house. My kid gets sick in the car. When we get home, I have to hit another button to "rent" the car another period so I can clean it, but it still gets sent back due to the emergency button being hit, and I can hit with a nice big fee due to cleanliness issues. I now need to go back out to get medicine, but five minutes by car is 30-45 min by walking. So it's another 15 minutes to get a car.
Even if all goes well, I could be looking at an additional 45 minutes just getting stuff done, as well as cost and loss of passenger quality because I don't own the vehicle. Hell, it could show up at my door full of shit, semen, and vomit, because some homeless guy is using it as his own personal hangout to sleep in. Or it could take even longer because I need to rent a driverless suv so I can bring furniture home to me, and those are relatively rare and command a premium to rent.
No one here is thinking of day to day use by all kinds of people, or what benefits ownership provides. I own my car, that means I dont have to worry about it showing up in a horrid state, I don't have to worry about paying large amounts for minor cosmetic damage, I don't have to budget extra time summoning the vehicle on site (which escalates the farther out from a city hub you are...you're doubling your travel time, and this would heavily penalize rural people), and there are a host of issues eliminated as well. Just the fact that I don't need to put a destination in is one thing. I can change my mind en route, I can wander, and if my wife calls me and tells me to come home, I can do so near instantly.