The concept of normal accidents was formulated by sociologist Charles Perrow in Normal Accidents: Living with High Risk Technologies (1984), but is related to a number of other analyses of accidents in complex, technological societies. Perrow used the concept to describe a type of accident that inevitably results from the design of complex mechanical, electronic, or social systems. The theory has had extended influence on subsequent analyses of accidents and errors related especially to advanced technologies.

Perrow's Normal Accidents

The unexpected and interactive failure of two or more components is not sufficient to cause a normal accident when there is enough time to solve the problem before it becomes critical. Instead normal accidents in Perrow's sense occur only in systems that, in addition to being complexly interactive, are also tightly coupled. One example would be two components whose failures start a fire while silencing the fire alarm...