Systems accident causes found

The root causes of most accidents are found during an analysis of the management system factors (Fig. 18-19). This major branch of the chart addresses the why issues. Specific factors and branches to be analyzed include... 

In canying ont the work function, the person has demands placed on his or her pltysical and psychological make-up. It is in this broader concept of the individual being part of a system where the real causes of accidents are found. However, it must be understood and accepted that the individual imports into a sterile world of machines and work schednles, inflnences which occur outside the work environment. Family, financial or health problems are often examples of major concerns to individuals. 

On viewing it as a system, it was found that although the driver was from a different area, he had been trained to check each trailer for wheel blocks, disconnect fill lines, and check safety-valve positions before ever moving it. This driver was in a hurry, thought the trailer had been properly prepared for transfer, and did not bother checking the connections. This was an important human element or cause of the accident. Taking this to the next level, we would ask, Why was the driver in a hurry and Was the culture of the site one that would routinely accept his taking these types of risk ... 

Another definition of an evaluation-case event is "that incident outcome for which an engineered solution or a management system solution could be found that would reasonably prevent its occurrence," or more simply put, an event that could be preventable. All human-caused accidents and the consequences of some natural occurrences (earthquake, wind, waves) can be defined as preventable. However, we are only interested in events where engineering and management system parameters could have prevented the accident provided they are within reasonable control of plant personnel. 

The primary causes of this event were a direct result of systems, which resulted in a low level of TMAA stability. We had enjoyed freedom from accidents for years because a great many people worked very hard to see that everything was in order however, there were not enough systems with built-in safeguards to ensure that the probability of failure was as low as we really wanted. This analysis pointed out the need for systems studies and subsequent improvements if we were to be satisfied with future performance. Space will not allow detailed discussion of all problems found and their ramifications however, key deficiencies are listed below without comment ... 

In 1990, the National Transportation Safety Board (NTSB) completed a study of 182 fatal-to-the-driver truck accidents to investigate the probable cause of the accidents. While the study was designed under the assumption that most fatal heavy truck crashes may be related to alcohol and other drugs, it was found that the most frequently determined probable cause was fatigue (12). A 1993 analysis of the Fatal Accident Report System (FARS) also suggested that truck driver fatigue is a contributing factor in about 30% of heavy truck accidents. 

The State Police report quoted a refrigeration serviceman who reported that all of the valves on the evaporator were shutoff and the fire chief found a steam hose steaming underneath the machine. The serviceman had previously seen steam used to melt ice buildup around the valves and to heat the oil in the machine to make it easier to drain the oil. [ 51 The District Engineering Inspector s report confirmed that the machine was completely isolated and the ammonia system was not protected by a safety valve or any type of pressure-relief device. The cause of the accident was the presence of the steam ho.se underneath the equipment to melt the ice on the drain valve or to help evacuate the system. The inspector s report could not determine if these preparations were intentional or accidental. 151... 

It sometimes happens in living systems that, when the primary element is not immediately available, a substitution can be made with an element with similar properties. Thus, an element from the same group can sometimes be substituted for an element not readily available. For instance, strontium (38) can sometimes be found to substitute for calcium (20) in the bones when strontium is more available than calcium. Radioactive strontium isotopes are sometimes released in nuclear accidents, so the incorporation of strontium into the bones is a cause for concern. 

Within aviation, analyzing the exact causes of accidents and incidents is a nontrivial task. Even if detailed flight data from the black box are available, it is usually still difficult to come up with a clear analysis, for the simple reason that the causes of incidents cannot be attributed to a single point of failure of one individual entity. Instead, most incidents in aviation are found to be caused by a complex interplay of processes at various levels of the socio-technical system, involving pilots, air traffic controllers, technical systems, and their interaction. For example the famous accident in 2009 of Air France Flight 447 is stiU under investigation and seems to have been the consequence of a rare combination of factors. On May 31, 2009, this flight disappeared... 

Investigations of industrial accidents reveal that most are caused by human error. The twentieth century s worst industrial disasters—Bhopal, Three Mile Island, and Chernobyl—helped clarify the complex chain of system problems that lead to human error. System problems are problems caused by a process system with built in design and operating deficiencies. The accidents provided numerous checklists and case studies for control room and equipment design. A partial list of some of the problems found at the industrial sites mentioned above are ... 

---