Cars have driven billions on miles on cruise control, but that does not mean that cruise control can autonomously drive a car. Planes fly billions of miles on a

Cars have driven billions on miles on cruise control, but that does not mean that cruise control can autonomously drive a car. Planes fly billions of miles on autopilot and yet we keep the pilots. What matters is not the number of miles driven, but the situations in which the system had no idea what to do and had to disengage, and moreover the variety of such situations. Indeed these situations are in the tail of the distribution, but that tail is a really challenging place. One series of accidents, particularly in conditions which would be easy to avoid by a human, and the whole market for the self driving car will pop like soap bubble.