System Safety Today

As society becomes more technically advanced, its tools become more and more sophisticated. In some cases, the machine has advanced further than the human capacity to control it. Jet fighters are good examples. These machines are capable of performing in g-forces that incapacitate most humans. Safety professionals need to be aware of the limits of human performance, as well as the fallibility of the individual in a mechanized system. 

Product liability is also a major concern for many companies. The McDonald s coffee award is a good example. In this case, a woman placed a cup of McDonald s coffee between her legs in a car. The coffee spilled and the woman was severely burned. McDonald s was found liable for the injuries, even though McDonald s cups contain a warning stating the contents are hot. 

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My first book, Safeware, presents a broad overview of what is known and practiced in System Safety today and provides a reference for understanding the state of the art. To avoid redundancy, information about basic concepts in safety engineering that appear in Safeware is not, in general, repeated. To make this book coherent in itself, however, there is some repetition, particularly on topics for which my understanding has advanced since writing Safeware. 

It appears, at least for now, that humans will have to provide direct control or will have to share control with automation unless adequate confidence can be established in the automation to justify eliminating monitors completely. Few systems exist today where such confidence can be achieved when safety is at stake. The problem then becomes one of finding the correct partnership and allocation of tasks between humans and computers. Unfortunately, this problem has not been solved, although some guidelines are presented later. 

At the 1993 International System Safety Conference, the then Chief of Air Force Safety in his keynote presentation said that the two challenges for the 90s were in software system safety and in human factors. This was true then, and it is today, more than ten years later. 

Fault hazard analysis is mentioned very frequently in system safety literature, sometimes as a type of analysis and occasionally as a technique. One NASA system safety document (NHB 1700.1-V3, System Safety) describes it as the analysis to be performed after the preliminary hazard analysis for further analysis of systems and subsystems and suggests that it can be either a separate analysis or an extension of the failure modes and effects analysis (NASA 1970). Most programs today (including NASA) refer to this analysis as the subsystem hazard analysis (SSHA) and the system hazard analysis (SHA). 

Today, various mathematics and probability concepts are being used to study various types of safety-related problems. For example, probability distributions are used to represent times to human error in performing various types of time-continuous tasks in the area of safety [3-7]. In addition, the Markov method is used to conduct human performance reliability analysis in regard to engineering systems safety [7-9]. 

In recent years patient safety has become an important issue because of a staggering number of deafhs and injuries due to patient safety-related problems. For example, as per an Institute of Medicine report around 100,000 Americans die each year due to human errors in the health care system [1], Today there are many patient safety organizations in various parts of the world that advocate improvement in patient safety. A patient safety organization may be described as a group, association, or institution that improves medical care by reducing the occurrence of medical errors. 

Today, the system safety process is still used extensively by the various military organizations within the Department of Defense, as well as by many other federal agencies such as NASA, the Federal Aviation Administration, and the Department of Energy. In most cases, it is a required element of primary concern in the federal agency contract acquisition process. 

Therefore, the question still remains as to the proper definition of safety. One possible improvement of the previously presented MIL-STD-882 definition might be that safety is a measure of the degree of freedom from risk in any environment (Leveson 1986). Hence, safety in a given system or process is not measured as much as is the level of risk associated with the operation of that system or process. This fundamental concept of acceptable risk is the very foimdation on which system safety has developed and is practiced today. 

Part 11 of this text details a number of the various common system safety analytical methods and techniques that are practiced in the system safety discipline. Each of these methods or techniques is usually conducted at specific points during the project or product life cycle, as indicated in Eigure 3.4. At this point, it is important to understand that a specific system or program may require the use of any or all of the system safety analysis techniques available to today s system safety professional. Each method has its own distinct purpose and function, and, as tools, each can be quite useful. 

Fault tree analysis as applied to system safety relies on preliminary hazard analyses (PHA) or other analysis techniques to identify major undesirable events. After constructing a tree, a system safety team applies qualitative or quantitative analyses to elements. To perform quantitative analysis on a tree, team members must apply a probability to each event cause. Today, computer systems make the... 

In general today s established system safety standards tend to be focused on development activities, or maintenanee of particular products or specific items. Typical safety standards in widespread use such as lEC 61508 (lEC 2010), Def Stan 00-56 (MoD 2007a) and DO-178B (RTCA 1992) generally cover service only in terms of maintenance or evolution of a system originally developed to the standard. 

Even today in the United States there are about 13 deaths daily in the workplace and 4 million injuries per year (Barab, 2012), which means we have to better integrate system safety into all engineering aspects. Studies conducted at Stanford University estimate the cost of accidents for nsers of conunercial and industrial construction at 1.6 billion annually. Hidden costs were found to be two to 18 times higher. Researchers also found that construction safety research over a 10-year period showed irrefutable... 

And of course, accidents are much worse if created on purpose. We are now much more at risk of any type of accidents resulting from software-controlled systems because of our trend toward open, interconnected, and networked systems. Throw into that cloud computing and mobile technology (mobile devices are now very common in troubleshooting industrial systems), and we can see that software is much more important to safety today than just a few years ago. Probably, one of the best examples is the new trend in smart cities, putting an entire city s control under software and cyber systems. 

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