'Swiss Cheese' Failure Model

[The Swiss cheese model of accident causation illustrates that, although many layers of defense lie between hazards and accidents, there are flaws in each layer that, if aligned, can allow the accident to occur. In this diagram, three hazard vectors are stopped by the defences, but one passes through where the "holes" are lined up.]

James Reason, who recently died at the age of 86, was most famous for his ""Swiss cheese" failure model (above and below) as exemplified by its mention at the top of his Wikipedia entry.

Below,

Reason explains it for you.

Charles Perrow's excellent 1984 book "Normal Accidents: Living with High-Risk Technologies," posits a variation of Reason's fundamental insight: Perrow called it "tight coupling."

From Wikipedia: "Perrow argues that multiple and unexpected failures are built into society's complex and tightly coupled systems, and that accidents are unavoidable and cannot be designed around."