A second factor is what we might call operator failure. Any abstract system, no matter how well designed it is, can fail to work as it is supposed to do because those who operate it make mistakes. This also applies both to social and natural systems. Unlike design faults, operator failure appears to be ineradicable. Good design can make the possibility of operator failure very low, and so can rigorous training and discipline; but so long as human beings are involved, the risk must be there. In the case of the Chernobyl incident, the root cause of the disaster was a mistake made in the operating of the emergency shutdown systems.

XREF: Connects to normal accident theory and the idea that human error is irreducible in complex systems.

Anthony Giddens, The Consequences of Moderni…, loc. 361