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Regardless of what triggered the Lac-Mégantic rail disaster, safety experts, veteran railroaders and even Canada’s own railroad history points to the fact that a single engineer should never have had the power to level six city blocks through mere neglect.

It’s harder, it’s messier and it’s more confusing to understand the factors that came together to cause such a tragedy

“We’re not well-programmed to see shades of grey, so we look for that one evil person to lay the blame at their feet,” said Marc Lalonde, a director with CKR Global Risk Solutions, a Canadian risk-mitigation firm.

“These are complex systems that are beyond the understanding of most of us … it’s harder, it’s messier and it’s more confusing to understand the factors that came together to cause such a tragedy.”

Speaking to a medical journal in 2012, renowned U.K.-based safety theorist James Reason summed up his career as talking up the “uselessness of blame.”

Revered by NASA rocket engineers and surgeons alike, Mr. Reason’s most famous legacy is the “Swiss cheese model,” which imagines safety checks to be like slices of cheese.

When a safety system is airtight and closely followed, the slices are cheddar: Rigid and impermeable to error.

Overtime, however, as employees grow complacent and safety standards slip, the slices begin to develop Swiss-cheese-like holes through which mistakes are allowed to pass.

If the holes are allowed to multiply, it is only a matter of time before a simple mistake can pass clean through all the layers of cheese and trigger a disaster.

“There is a growing appreciation that large scale disasters … are the result of separate small events that become linked and amplified in ways that are incomprehensible and unpredictable,” wrote the U.S. organizational theorist Karl E. Weick in a 1990 analysis of the 1977 Tenerife air disaster, in which two fully-loaded 747s collided at a Canary Islands airport.