It'd be a shame if makers of self-driving cars stuck to actual cars and single trips.

Something in between that and buses might be very efficient and practical, especially for things like work commutes, visits to the supermarket and the like. Having say 6 or 8 seats and picking up multiple parties who are heading in the same direction or going to roughly the same destination. It would likely be quicker than waiting for a single trip car and definitely cheaper. Additionally it would likely reduce the number of autonomous vehicles on the road and use less resources.