What Keller is saying is that moving a car is super dumb, as the output of the computer is going forward backward, left or right. Only 4 possibilities. And he's probably thinking mostly of highway or parking lot navigation. Very predictive on highway, and on parking lots you're just trying to avoid collisions (which is quite easy thanks to low speeds). <br>What Lex is saying is the grey zone in between those two situations (city driving) is much harder to grasp and navigate. An object that pops up in a parking lot (lets say an erratic child) is avoidable thanks to your low speed. The same object that pops up in a city becomes unavoidable. You're going to hit the erratic child if you're going 25-30mph. So the difficulty Lex is referring to, I think (he's pointing out pedestrians and cyclists), is predicting these erratic behaviors so as to not put the computer in such a situation.,(reply>), ramon plutarque if the car navigates better than a human and you have to make up scenarios like bee-in the face to try and come up with maybe; then i believe the 98% comes into play.,(reply>), @Michael Dautel Of course, but a radar isn't Xray, so won't see a child behind a parked car. And the problem isn't detecting, that's been solved already, the problem is predicting a behavior. Is the child standing on the side walk going to start running in the middle of the road, so should you slow down? Is the cyclist going to swerve hard to the left because there's a stick on the road, or a bee in his face, so should you wait before passing?,(reply>), ramon plutarque radar and sensors can detect multiple targets before a human driver is even aware they exist.