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Human Factors Engineering1Introduction1.1Human Factors Engineering DefinedBefore attempting to define human factors engineering,we should say a word about the term.Human factors engineering is the term used in the United States and a few other countries.The term ergonomics,although used in the United States,is more prevalent in Europe and the rest of the world.Some people have tried to distinguish between the two,but we believe that any distinctions are arbitrary and that,for all practical purpose, the terms are synonymous.Another term that is occasionally seen(especially within the itary)is human engineering.However,this term is less favored by the profession, and its use waning.Finally,the term engineering psychology is used by some psychologists in the United States.Some have distinguished engineering psychology,as involving basic research on human capabilities and limitations,from human factors engineering,which is more concerned with the application of the information to the design of the things.Suffice it to say,not everyone would agree with such a distinction.We approach the definition of human factors engineering in terms of its focus, objectives,and approach.1.2Focus of Human factors engineeringHuman factors engineering focuses on human beings an their interaction with products,equipment,facilities,procedures,and environments used in work and everyday living.The emphasis is on human beings(as opposed to engineering,where the emphasis is more on strictly technical engineering considerations)and how the design of things in influences people.Human factors engineering,then,seeks to change the things people use and the environments in which they use these things to better match the capabilities, limitations,and needs of people.1.3Objectives of Human factors engineeringHuman factors engineering has two major objectives.The first is to enhance the effectiveness and efficiency with which work and other activities are carried out. Included here would be such things as increased convenience of use,reduced errors,andincreased productivity.The second objective is to enhance certain desirable human values, including improved safety,reduced fatigue and stress,increased comfort,greater user acceptance,increased job satisfaction,and improved quality of live.It may seem like a tall order to enhance all these varied objectives,but as Chapanis (1983)points out,two things help us.First,only a subset of the objectives are generally of highest importance in the specific application.Second,the objectives are usually correlated.For example,a machine or product that is the result of human factors engineering technology usually not only is safer,but also is easier to use,results in less fatigue,and is more satisfying to the user.1.4Approach Of Human Factors EngineeringThe approach of human factors engineering is the systematic application of relevant information about human capabilities,limitations,characteristics,behavior,and motivation to the design of things and procedures people use and the environments in which they use them.This involves scientific investigations to discover relevant information about humans and their responses to things,environments,etc.This information serves as the basis for making design recommendations and for predicting the problem effects of various design alternatives.The human factors engineering approach also involves the evaluation of the things we design to ensure that they satisfy their intended objectives.Although no short catch phrase can adequately characterize the scope of the human factors engineering field,such expressions as designing for human use and optimizing working and living conditions give a partial impression of what human factors engineering is about.For those who would like a concise definition of human factors engineering which combines the essential elements of focus,objectives,and approach discussed above,we present the following definition,modified slightly from Chapanis(1985):Human factors engineering discovers and applies information about human behavior,abilities,limitations,and other characteristics to design of tools, machines,systems,tasks,jobs,and environments for productive,safe,comfortable,and effective human use.2Human Error2.1Human ErrorTo some people the term human error has a connotation of blame or curser.A much more productive approach,however,is to consider human error simply as an event whose cause can be investigated.Numerous definitions have been proposed for human error,but the following embodies the essence of most of them:human error is an inappropriate or undesirable human decision or behavior that reduces,or has the potential for reducing, effectiveness,safety,or system performance.Two things should be noted about this definition.First an error is defined in terms of its undesirable effect or potential on system criteria or on people.Forgetting to pack cookies in a lunch would not be considered a human error in the context of a construction crew building a bridge,but forgetting to take safety shoes and glasses to the work site would be.Second,an action does not have to result in degraded system performance or an undesirable effect on people to be considered an error.An error that is corrected before it can cause damage is an error nonetheless.The important point is that an action must have the potential for adversely affecting system or human criteria.Although there is a tendency among some to view errors as those of“operators”, other people involved in the design and operation of systems also can make errors,such as equipment designers,managers,supervisors,and maintenance personnel.Therefore,in talking about human error,we should consider the entire system and not focus only on the operator.If human error involves inappropriate or undesirable behavior,then it is important to understand how one determines what behavior is appropriate or desirable.Rasmussen (1979)points out that such determinations are often set by some one conducting a rational,careful evaluation of the behavior after the fact.In essence,what is considered to be a human error is somewhat arbitrary because the determination of what is appropriate may not have been established until the error was identified.In addition, Rasmussen(1987)feels that the identification of an event as a human error depends entirely upon the stop rule applied during the investigation.If system performance is judged to be lower than some standard,someone will typically try to backtrack to find the cause.How far back to go is an open question.One could stop at the operator’sactions and call the event a human error,or one could investigate what caused the human to act as he or she did.The cause may then be traced to other factors,such as faulty equipment,poor management practices,inaccurate or incomplete procedures,etc. Rasmussen(1982)makes a provocative point that an action might become an error only because the action is performed in an unkind environment that does not permit detection and reversal of the behavior before an unacceptable consequence occurs.2.2Human Error Classification SchemesVarious error classification schemes have been developed over the years.An effective classification scheme can be of value in organizing data on human errors and for giving useful insights into the ways in which errors are caused and how they might be prevented.Over the years,there have been numerous attempts at developing a practical taxonomy of human errors.We will briefly discuss a few such schemes to illustrate the thinking in the area.Discrete-action classifications one of the simplest classification schemes for individual,discrete actions is that used by Swain and Guttman(1983)●Errors of omission●Errors of commission●Sequence errors●Timing errorsErrors of omission involve failure to do something.For example,an electrician was electrocuted while attempting to position himself on the steel framework of an electrical substation.There were several points to disconnect in order to shut off power completely to the substation,and he apparently forgot to disconnect one of them.Errors of commission involve performing and acting incorrectly.For example,a mechanic sitting on a conveyer belt called for his partner to lightly hit the start button to jog the belt forward a few inches.The helper lost his balance momentarily and hit the button hard enough to actually start the belt moving at full speed,rather than just jogging it forward.The mechanic was pulled between the belt and a steel support high(23cm) above it.A sequence error(really a subclass of errors of commission)occurs when a personperforms some task,or step in task,out of sequence.An example occurred in the case of a crane operator who was lifting a24-ton block of stone.Rather than lifting the boom and then rotating it90degrees,he rotated the near flat extended boom first,and before he could lift it,and crane overturned.A timing error(also a subclass of errors of commission)occurs when a person fails to perform an action within the allotted time,either performing too fast or too slowly. Taking too long to remove one’s hand from a work piece in a drill press,for example,is a timing error that can result in a nasty injury.2.3Dealing With Human ErrorIt is inevitable that human will err.There are numerous specific strategies for reducing the likelihood or negative consequences of human errors,but we do not try to enumerate them here.However,a brief discussion of generic approaches might be useful. In general,the likelihood or consequences of errors can be reduced by personnel selection and training and by design of the equipment,procedures,and environment.Selection:Selecting people with the capabilities and skills required to perform a job will result in fewer errors being made.Such things as perceptual,intellectual,and motor skills should be considered.The limitations with this approach are that(a)it is not always easy to determine what skills and abilities are required,(b)reliable and valid test do not always exist for measuring the required skills and abilities,and(c)there may not be an adequate supply of qualified people.Training:Errors can be reduced by proper training of personnel.Unfortunately, people do not always perform as they were trained.They can forget or revert to old habits acquired before training.Training can also be expensive because it must be given to each person and,in critical situations,should include refresher training as well.We will have a little more to say about training later.Design:One of the important themes of this book is that the design of equipment, procedures,and environments can improve the performance of people,including reducing the likelihood and consequences of errors.There are three generic design approaches for dealing with human error:Exclusion designs:the design of things makes it impossible to commit the error●Prevention designs:the design of things makes it difficult,but not impossible,to commit the error●Fail-safe designs:the design of things reduces the consequences of errorswithout necessarily reducing the likelihood of errorsDesigning to reduce errors or their consequences can often be the most cost-effective approach to the problem of human error.A system need designed online once,while selection and training must be repeated as new people become part of a system.In essence,it is easier to bend metal then to twist arms.Senders(1983)and Rasmussen(1987)make an interesting point with respect to eliminating human error.They point out that humans are servomechanisms and must experiment with their environment to learn and acquire skill.They maintain that errors are a natural consequence of this experimentation and trial-and-error learning.Errors, they contend,are necessary for the development of skilled performance.Their emphasis would be on how to provide“safe”opportunities for making errors(e.g.in training)or how to structure the environment to improve error detection and correction.。