How do automatic car washes prevent damage to vehicle

Question

How do these automatic car washes with hunks of rotating metal not completely obliterate cars as they go through, and how fool proof are the systems that prevent them from going haywire?

In: 1

Answer 1

Pressure sensors attached to the washing arms tell a PLC controller to stop pushing forward and start the next step (usually to wash the sides and roof of the vehicle.)

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Edit: The systems are like 99% accurate. The same systems used to wash your car are used in large scale industrial fabrication.