The goal is not to never encounter a car, but that the encounter is mediated with very robust and proven technology that is compatible with both human and curre

The goal is not to never encounter a car, but that the encounter is mediated with very robust and proven technology that is compatible with both human and current level AI, like a V2X enabled trafic light or a steel bollard. A car can still hit the pod if it disobeys the red light, but the driver would be culpable and the incident itself would be similar to a car hitting, say, a bike - not the fault of the bike. As for the density of such infrastructure, you don't need it on every street, just within a short walking distance to be practical, a few hundred meters maybe. Once you can reach the hail point, it can take you non-stop to any other in the area served, so something like 30 Km/h top speed can go a long way.