A Few Words about Hindsight Bias and Examples

One of the most common mistakes in accident analyses is the use of hindsight bias. Words such as could have or should have in accident reports are judgments that are almost always the result of such bias [50]. It is not the role of the accident analyst to render judgment in terms of what people did or did not do (although that needs to be recorded) but to understand why they acted the way they did. 

Although hindsight bias is usually applied to the operators in an accident report, because most accident reports focus on the operators, it theoretically could be applied to people at any level of the organization The plant manager should have known. ..  

The biggest problem with hindsight bias in accident reports is not that it is unfair (which it usually is), but that an opportunity to learn from the accident and prevent future occurrences is lost. It is always possible to identify a better decision in retrospect—or there would not have been a loss or near miss—but it may have been difficult or impossible to identify that the decision was flawed at the time it had to be made. To improve safety and to reduce errors, we need to understand why 

As an example, consider a real accident report on a chemical overflow from a tank, which injured several workers in the vicinity [118]. The control room operator issued an instruction to open a valve to start the flow of liquid into the tank. The flow meter did not indicate a flow, so the control room operator asked an outside operator to check the manual valves near the tank to see if they were closed. The control room operator believed that the valves were normally left in an open position to facilitate conducting the operation remotely. The tank level at this time was 7.2 feet. 

The outside operator checked and found the manual valves at the tank open. The outside operator also saw no indication of flow on the flow meter and made an effort to visually verify that there was no flow. He then began to open and close the valves manually to try to fix the problem. He reported to the control room operator that he heard a clunk that may have cleared an obstruction, and the control room operator tried opening the valve remotely again. Both operators stUl saw no flow on the flow meter. The outside operator at this time got a call to deal with a problem in a different part of the plant and left. He did not make another attempt to visually verify if there was flow. The control room operator left the valve in the closed position. In retrospect, it appears that the tank level at this time was approximately 77 feet. 

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