Boeing 737 Max crashes because those airlines
didn't pay extra to get a redundancy system to verify whether the Angle of Attack reading was correct or it was an error. Without that extra payment for the redundancy error checker, the error was automatically accepted by the machine as the correct reading and it nosed the plane down and killed everyone on board.
If they paid extra money, they would get an angle of attack disagreement indicator Light, the pilots would know that there's a reading error. Also if they paid extra for the extra exterior sensor on the other side of the plane, then both the machine and the pilots would know there's a reading error between the 2 sensors.
So in the case above, redundancy is an error checking routine/protocol and the redundancy system requires many parts as well as money (regulators try to make safety standard and not optional with extra charge. So the laws can also be included in the redundancy system).
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I guess the "redundant" definition depends on who defines it.
Bosch defines it as:
"Everything in view at all times
Cameras, lidar and radar sensors are the eyes of the assistance systems. With their 360-degree viewing capabilities, they supply important information about the surroundings. By backing each other up, the vehicle still has everything in view even if the single sensors fail."
That despite the LIDAR cannot read traffic lights, the camera cannot read darkness, and the radar ignores stationary objects.
It's just when MobilEye defines it, some people just don't allow such a definition.