Presumably when autonomous cars hit a saturation point on our roads they will be sufficiently well connected to communicate their direction/velocity and immediate obstacles to all other nearby autonomous vehicles (and sending red flags to each other about non-connected vehicles piloted by meatbags). A little intelligent communication and all the traffic on a road will be able to pre-emptively make space for a vehicle to swerve to avoid errant pedestrians. That way the cars don't actually need to slow down, they can just perform a high speed ballet, working together to keep traffic flowing freely.
I am possessed by hopeless optimism here.