An automated taxi service is certainly one of the things we ought to get out of this navigation technology (but you don't want to call it a taxi service, because you don't want to be subjected to the limits and fees placed on taxis by municipalities), but apparently if you look at commuter rail systems, you find that people tend to commute from suburbs to downtown in the morning, and back out in the evening. Commuter rail systems usually want to have separate overnight layover facilities on the outbound ends of routes, vs mid-day layover facilities in the downtown areas. You can force the cars to rack up empty miles, but it's probably more energy efficient to have separate mid-day and overnight parking.

The other thing the automated taxis should offer as an option is cars with multiple compartments, where if you wanted to get from one compartment to another you'd have to get out of the car. People who are impatient but don't care too much what their trip costs could request that they get one compartment of the car and it get routed so that they aren't delayed by other people in sharing the car, and then people who want cheap transportation and don't care so much how long it takes could book the other compartments. You could also have a hybrid option where the impatient would allow up to 5 minutes (or any number of minutes of the rider's choosing) delay to allow others to be picked up/dropped off, and there could be transfer points along major roads, and people wanting cheap travel could express a willingness to deal with N transfers. That could go a long way towards increasing the number of people in the average vehicle.