I’m not convinced that’s true. The friction involved with public transit (limitations schedules, routes, and sharing of vehicles) are enough to limit much of the usage outlined in the above comment.
Vehicle fleets don't solve the spatial and temporal realities that are reflected in the schedules and routes of public transit. A fleet of vehicles has to be staged to meet fluctuating demands.
Mathematically, on demand vehicles are probably harder to schedule because of random variation in queuing. Consider a population of workers each of which sometimes works from home. Some days an unusually high, but not statistically unlikely, number of riders all stay home: the idling vehicles need to sit somewhere. Other days, a statistically likely but atypical number of riders don't work from home and there are not enough vehicles to go around.
Public transit addresses fluctuation with a low nominal cost of providing surplus capacity to normal operation in the form of standing room. Public transit can be sized more closely to peak demand. On the other hand, from 20:00 to 06:00 the peak demand capacity of an autonomous car fleet needs to be parked somewhere. Between 06:00 and 08:00 and again between 18:00 and 20:00 the fleet needs to be moved to storage.
Mathematically, on demand vehicles are probably harder to schedule because of random variation in queuing. Consider a population of workers each of which sometimes works from home. Some days an unusually high, but not statistically unlikely, number of riders all stay home: the idling vehicles need to sit somewhere. Other days, a statistically likely but atypical number of riders don't work from home and there are not enough vehicles to go around.
Public transit addresses fluctuation with a low nominal cost of providing surplus capacity to normal operation in the form of standing room. Public transit can be sized more closely to peak demand. On the other hand, from 20:00 to 06:00 the peak demand capacity of an autonomous car fleet needs to be parked somewhere. Between 06:00 and 08:00 and again between 18:00 and 20:00 the fleet needs to be moved to storage.