“Another underlying assumption is that the production workers’ key role is to identify and call attention to problems even if it leads to stopping production. This requires an environment of trust in which there is no question whether pulling the andon [to signal that there is a problem] is the right choice; workers must not fear a reprimand and, in fact, may receive praise for identifying a problem.” 

Toyota Culture  by Jeffrey Liker & Michael Hoseus (McGraw Hill, 2008) p. 7.