David Harkey, president of I.I.H.S., said that the industry’s reality check over the technical challenges, and attendant public disillusionment, is masking genuine progress. For one, the building blocks of partial autonomy cars are already in every showroom. Automated emergency braking is standard on every new car as of September, thanks to a voluntary agreement forged in 2016 among automakers, I.I.H.S. and the National Highway Traffic Safety Administration.

Such radar- or camera-linked brakes have cut police-reported rear-end collisions by a striking 50 percent, Mr. Harkey of the I.I.H.S. said, according to their research, adding that automated pedestrian braking has reduced the number of car-human collisions by 30 percent versus cars without the feature. And anti-lock brakes; cameras, radar and ultrasonic sensors to manage blind spot and lane departure monitors; and adaptive cruise control have become standard as well.