> A car comes by, doesn't look right, anyone could pull the cord and stop the line while the problem was understood.

Yeah, but I bet that anyone frivolously pulling the cord would find themselves out of a job.

To pull the cord would take great confidence. To have spotted a real production issue would have to be met with praise.

Eh, obviously?

The point being it isn't fundamentally different from going to your supervisor. In both cases you're going to get judged on your decision.