@lauren Human-driven taxis are never going to replace private cars, unless you bring in a servile class to drive them.
Robot taxis could eventually be the primary mode of transport in cities. You could then have smaller parking lots, and charge people to park.
Robot taxis could either seat four with hard partitions between them so people would feel safe sharing, or they could be half-wide and share the lanes.
They can form convoys when they are all going to the same area, reducing traffic.