A Guide to Human Factors and Ergonomics

Martin Helander

• Verlag: CRC Press
• Jahr: 2005
• ISBN:
  9781134458677
• Auflage: 2
• Thema: Technik & Maschinenbau
• Thema: Maschinenbau Allgemein

Completely revised and updated, A Guide to Human Factors and Ergonomics, Second Edition presents a comprehensive introduction to the field. Building on the foundation of the first edition, titled Guide to Ergonomics of Manufacturing, the new title reflects the expanded range of coverage and applicability of the techniques you will fin

Part I: Information—Centered Human Factors

1: Introduction to Human Factors and Ergonomics

Science never appears so beautiful as when applied to the uses of human life.

Thomas Jefferson

1.1 INTRODUCTION

The purpose of this chapter is to give an overview of human factors and ergonomics (HFE) and to show how these two sciences developed—ergonomics in Europe and HFE in the U.S.

The word ergonomics is derived from the Greek words ergo (work) and nomos (laws). It was used for the first time by Wojciech Jastrzebowski in a Polish newspaper in 1857 (Karwowski, 1991). In the U.S., human factors engineering and human factors have been close synonyms. European ergonomics has its roots in work physiology, biomechanics, and workstation design. Human factors, on the other hand, originated from research in experimental psychology, where the focus was on human performance and systems design (Chapanis, 1971).

But there are several other names, such as engineering psychology, and more recently cognitive engineering and cognitive systems engineering. The latter emphasizes the importance of human information processing for our science (Hollnagel and Woods, 2005).

Despite the differences between human factors and ergonomics in the type of knowledge and design philosophy, the two approaches are coming closer. This is partly due to the introduction of computers in the workplace. Design of computer workplaces draws from a variety of human factors and ergonomics knowledge (see Table 1.1). We can illustrate the problem as shown in Figure 1.1. Here a user of a computer is perceiving information on a display. The information is interpreted and an appropriate action is selected. The action is executed manually as a control input, which in turn affects the information status on the display. A new display is generated.

To solve a problem that is related to computer workplaces, an ergonomist must be able to identify the problem, analyse it, and suggest improvements in the form of design solutions. This leads to our first maxim:

The primary purpose of human factors and ergonomics is design.

In designing a workplace, the existing situation must first be analysed, new design solutions must be synthesized, and these design solutions must be analyzed again. The design process may be described using a control loop, as shown in Figure 1.2. Through successive design iterations, sometimes over extended periods of time, design is improved. In fact, even simple designs, such as that of the paper clip, took more than 120 years to mature, from the first patent in 1814, which was for a paper pin, to the present paper clip, which was patented in 1934 (Petroski, 1992). We can understand from this example that the design of complex systems such as computers is still in its infancy.

TABLE 1.1 Design Problems and Corresponding Knowledge Arising from the Introduction of Computers in the Workplace

FIGURE 1.1 Analysis of the human-machine interface requires interdisciplinary knowledge of biomechanics, cognitive psychology, and systems design methodology.

It follows that interdisciplinary knowledge is required in ergonomics design for the following reasons: (1) to formulate systems goals; (2) to understand functional requirements; (3) to design a new system; (4) to analyze a system; and (5) to implement a system. From the feedback loops in Figure 1.2 it also follows that design is a never-ending activity. There are always opportunities for improvements or modifications.

FIGURE 1.2 Procedure for design and redesign of a system.

The interdisciplinary nature of ergonomics is obvious when one notes the mixed professional background of ergonomists. They come from a variety of professions— engineering, psychology, and medical professions, to mention a few.

Many HFE experts are designers. A common design scenario may be as follows. Imagine that the system in Figure 1.1 was redesigned with three displays rather than one, and that some of the operator’s decisions were taken over by a decision support system, and that the user’s input to the computer system was made by voice recognition technology rather than manual keying. This type of system is currently used in fighter aircrafts. In designing such a system the HFE specialist would have to consider many issues:

• Should the user always be in charge, or are there situations where the computer should take over and fly the aircraft automatically? If so, define in what situations the computer should take over.
• How should the information on the three displays be laid out? What type of information should go on what display? Do we gain anything from using color displays (which are expensive)?
• Can a voice recognition system understand the pilot despite the noisy background? How can one avoid misrecognitions by the computer? We had better make sure that critical commands, such as “fire,” are correctly understood.
• Are there design constraints, such as economic and organizational constraints, and possibly constraints from a labor union? Some important constraints are dictated by training requirements. Pilots may be confused if the new model of an aircraft is very different from the old model, and they may revert to the control behavior for the old aircraft, particularly under stressful conditions.

The HFE specialist will analyze the situation and obtain information from users and management. To come up with a good design it will be necessary to get information about the design of similar systems. Many good design ideas can be found in textbooks and scientific articles. The HFE specialist will generate a few design alternatives, which will then be evaluated. The HFE specialist will then have to select an evaluation tool. There are many options, including rapid prototyping, usability studies, or performing an experiment with users as test subjects.

This scenario leads to our second maxim:

In HFE, a systematic, interdisciplinary approach is necessary for design and analysis.

1.2 DEFINITION OF HUMAN FACTORS AND ERGONOMICS (HFE)

There are many definitions in the HFE literature. The following is from Helander (1997):

• Considering environmental and organizational constraints,
• Use knowledge of human abilities and limitations
• To design the system, organization, job, machine, tool, or consumer product
• So that it is safe, efficient, and comfortable to use.

Note again that the main purpose is design (Chapanis, 1995). Ergonomics is thereby different from most of the bodies of knowledge that are used to support HFE. Ergonomics is different from anthropology, cognitive science, psychology, sociology, and medical sciences, since their primary purpose is to understand and model human behavior—but not to design.

The International Ergonomics Association (2000) provides the following definition:

“Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance.”

“Ergonomists contribute to the design and evaluation of tasks, jobs, products, environments and systems in order to make them compatible with the needs, abilities and limitations of people.”

Throughout the book, I will use the terms ergonomics, human factors, and HFE interchangeably. I will assume that there are no differences between these words, although, as we shall see below, the histories of human factors and ergonomics are quite different.

1.3 THE EARLY DEVELOPMENT OF HUMAN FACTORS AND ERGONOMICS (HFE)

One may argue that designing for human use is nothing new. Hand tools, for example, have been used since the beginning of mankind, and ergonomics was always a concern. If hand tools are appropriately designed they can concentrate and deliver power, and aid the human in tasks such as cutting, smashing, scraping, and piercing. Various hand tools have been developed since the Stone Age, and the interest in ergonomic design can be traced back in history (Childe, 1944, Braid wood, 1951).

Bernardino Ramazzini was a professor of medicine at Padua and Modena in Italy. In 1717 he published a book called The Diseases of Workers, which documented links between many occupational hazards and the type of work performed. He described, for example, the development of cumulative trauma disorder, which he believed was caused by repetitive motions of the hand, by constrained body posture, and by excessive mental stress. Although he did not have the present tools of science to support his findings (such as statistical testing), he proposed many innovative solutions to improve the work place.

The Frenchman LaMettrie’s controversial book L’homme Machine (Man, the Machine) was published in 1748, at the beginning of the Industrial Revolution (Christensen, 1962). He examined the analogies between humans and machines and concluded that people are…quite similar. Two things can be learned from LaMettrie’s writings. First, the comparison of human capabilities and machine capabilities was a sensitive issue already in the 18th century. Second, by considering how machines operate, one can learn much about human behavior. Both issues remain debated in ergonomics in our day. For example, an industrial robot has many constraints. Some assembly tasks are really difficult for a robot to do, such as putting a washer on a screw before the screw is tightened. Therefore, in the design of new products one must consider “design for assembleability.” There can be no washers in the design, there can be no precision tasks that are difficult to program, and so forth. It turns out that the same design features are also very helpful for human assembly operators; we just did not think about this issue until we had to deal with robots. It seems a great irony that only with the introduction of robots did designers start to consider the requirements of the human operator (Helander, 1995).

Rosenbrock (1983) pointed out that during the Industrial Revolution in England there were efforts to apply the concepts of a “human-centered design” to tools such as the Spinning Jenny and the Spinning Mule. The concern was to allocate interesting tasks to the human operator, but let the machine do repetitive tasks. This is another common reason for robotics in our days: to make the work more interesting we must remove repetitive and uninteresting tasks.

At the beginning of the 20th century, Frederick Taylor introduced the scientific study of work. This was followed by Frank and Lillian Gilbreth, who developed the time and motion study and the concept of dividing ordinary jobs into several small elements called “therbligs” (Konz and Johnson, 2004). Today, there are objections against Taylorism, which has been seen as a tool for exploiting workers. This is because there are behavioral aspects of work simplification: give a person a repetitive and mindless job, and there is a great risk that the person will turn mindless. Nonetheless, time and motion study remains useful for measuring and predicting work activities, such as the time it will take to perform a task (Helander, 1997). These are valuable tools if used for the right purpose!

1.4 THE CURRENT DEVELOPMENT OF HUMAN FACTORS IN THE U.S. AND EUROPE

In the beginning of the 20th century, industrial psychology did much research to find principles for selecting operators who were the most suitable to perform a task. The research on accident proneness is typical for the 1920s. Accident proneness assumes that certain individuals have certain enduring personality traits, which make them more prone to have accidents than others. This is because they have a “bad personality.” If one can understand how these individuals differ from “normal” people, one can exclude them from activities where they will incur accidents. This approach, which dominated research for about 40 years, was not fruitful. It turns out that accident proneness and many personality features are not stable features, but change with age and experience (Shaw and Sichel, 1971). A person may have many accidents in his young age, but 10 years later he is a different person with no accidents. In current ergonomics there is a realization that human error is mostly caused by poor design, and one should not blame operators for accidents. Instead the goal should be to design environments and artifacts that are safe for all users.

In Europe, ergonomics started seriously with industrial applications in the 1950s, and used information from work physiology, biomechanics, and anthropometry for the design of workstations and industrial processes. The focus was on the well-being of workers as well as on improved manufacturing productivity. Ergonomics was well established in the 1960s, particularly in the U.K., France, Germany, Holland, Italy, and the Scandinavian countries. In many European countries, labor unions took an early interest in promoting ergonomics as being important for worker safety, health, comfort, and convenience. The labor unions are particularly strong in the Scandinavian countries, in France, and in Germany, where they can often dictate what type of production equipment a company should purchase. Good ergonomics design is now taken for granted. As a result, even heavy equipment, such as construction machines, is designed to be very comfortable and convenient to operate.

In the U.S. human factors emerged as a discipline after World War II. Many problems were encountered in the use of sophisticated equipment such as airplanes, radar and sonar stations, and tanks. Sometimes these problems caused human errors with grave consequences. For example, during the Korean War, more pilots were killed during training than in actual war activities (Nichols, 1976). This surprising finding led to a review of the design of airplanes as well as procedures and strategies in operation. Several new design issues were brought up:

• How can information be better displayed so that pil...