Just imaging self-driving minibuses.
Public transport minibuses might actually be a good place to exercise self driving vehicles.
Minibuses don't need the same versatility as consumer cars have. They "only" need to be able to handle anything they can encounter on a predefined route. The route itself could even be optimized for them (eg pedestrian barriers).
IMO the best application of self-driving cars in an urban landscape is last-mile demand for people who live outside the city, where it's not economical to run buses or trains. But inside a city proper, or even on a busy freeway, having one car per passenger takes up a lot of space that could be better used elsewhere, both while moving and while parked.
(Also, self-driving technology could be applied to buses and streetcars to reduce operating costs and expand frequency and range of service.)