how much have cars safety improved in terms of crashes, airbags, etc, versus the robot will stop the crash?

Impossible to measure, many other uncontrolled variables - esp. significant improvements to infrastructure in Europe, and regulations. Take NL, where a crash involving a pedestrian or a cyclist effectively forces the driver to prove their innocence. I can walk across a Dutch town blindfolded with the biggest risk to my wellbeing being cyclists (well, and the canals). I'd guess the impact of those intervention dwarfs the "i will beep at you until i make you deaf if you don't put your seatbelt over your grocery bag" innovations.