Human Factors Methods for Design

Making Systems Human-Centered

Christopher P. Nemeth

• Editore: CRC Press
• Anno: 2004
• ISBN:
  9781134429202
• Edizione: 1
• Argomento: Tecnologia e ingegneria
• Categoria: Ingegneria generale

There is no shortage of available human factors information, but until now there was no single guide on how to use this information. Human Factors Methods for Design: Making Systems Human-Centered is an in-depth field guide to solving human factors challenges in the development process. It provides design and human factors professionals, sys

Part I
Human factors practice

How has the human-made world come about?
Chapter 1—The human-made environment

What can humans do? What will humans do? Why?
Chapter 2—Human abilities and limits

What internal influences affect problem solving in research and development?
Chapter 3—How we think about development problems

What is research and development and what external influences affect it?
Chapter 4—What influences development

How does one go about human-centered research?
Chapter 5—Human factors in research and development

1 The human-made environment

What is a system? A product? A service?
1.1 The systems model
What is performance and how is it measured?
1.2 Requirements
How do products evolve?
1.3 Life cycle
How are products created? What is the role of research and development?
1.4 The development process
What implications does technology present for people?
1.5 System issues
What skills comprise human factors? How has the field evolved?
1.6 Human factors practice

Every day, people around the world who are at work and play enjoy the use of products, buildings and services. Much of the human experience each day relies on items that were made to extend human abilities and to overcome human limits. The sum of all the products, services, environments and systems that humans have produced comprises the operational environment (OE). The inner environment of the individual is separate and apart from the rest of physical existence that comprises the outside environment. ‘This artificial world’, psychologist and computer scientist Herbert Simon (1998:113) contends, ‘is centered precisely on this interface between the inner and outer environments; it is concerned with attaining goals by adapting the former to the latter.’

Historically, craft-based societies relied on experienced individuals to fabricate a small number of items that were gradually refined through trial and error. Each time another item (e.g. clothing, tool, house) was produced, it reflected the collective knowledge of the artisan(s) who made it. Mechanization broke the traditional link between design knowledge and production that is inherent in craft. Machines could be used to manufacture interchangeable parts more cheaply and in greater numbers than could be produced by individual artisans.

The advent of mass production posed questions about economies of scale, variety, efficiency and cost. Attention was focused on the nature of physical work. Decisions had to be made on the appropriate rate of work for both machines and the people who used them. What was needed was an objective measurement and order of work through an understanding of work’s natural laws, or ‘ergonomics.’ Since that time, the evolution of ergonomics and human factors has continued to serve in a complimentary role to design and engineering. In that sense, human factors and ergonomics inform the process of creating the operational environment.

An increasing percentage of daily life in developed countries is spent in the operational environment. As a result, the nature of the OE shapes and influences perceptions in many ways that we are (and are not) aware of. For example, the development of automation and computing systems has created a growing number of products that incorporate software programs to perform routine tasks. Many are now able to govern themselves in limited ways under the guidance of artificial intelligence (AI) software.

Products, spaces and systems that work well routinely go unnoticed. Yet, if an accident occurs which causes loss of property or life, if productivity sags, or if a breakdown causes usually reliable services to fail, the most frequently asked question is ‘why?’ This is followed by ‘what could have been done to avoid this?’ Often, the answer lies with the way the product was designed, the environment in which it was used or the way it was used.

Understanding systems and how they work is a key to the creation of products that work well. Most products (even simple ones) are comprised of multiple components and are accompanied by related services. As a result, it is most helpful to use a system model to understand them. This chapter describes systems, their traits, and the process, and the roles of professionals, involved in their creation.

Humans are in and of their systems; they are not apart from them.

(Julie Christensen)

1.1 The systems model

A system is any collection of elements that is organized to achieve a purposeful result. An operating room is a health care system, designed to restore its users to better health. A carnival is an entertainment system that is designed for its customers’ enjoyment. A factory is a production system that is created to produce artifacts. An aircraft is a transportation system that is created to deliver cargo and people to desired sites.

Where a system begins and ends is not always clear. Even when systems can be clearly delineated, their interdependence (see Section 1.5.2) and interactions can have a significant effect on other systems.

Goals and objectives are used to develop a system. However, it is human performance that defines and animates the system.

A system’s purpose is a desirable goal state that system operation is to achieve. The performance of system elements yields results that are intended to fulfill the system’s purpose.
Objectives such as cost impose limits on how those results will be accomplished.

1.1.1 System elements

Figure 1.1 shows Christensen’s (1985a) model of system composition and performance that identifies three classes of elements: hardware/software, personnel and procedures.
Hardware/software includes machines and their controls, displays, mechanisms and software programs. Personnel are the humans who perform in roles as operators, maintainers and end users. Managers are personnel who supervise the performance of operators and maintainers.

The term personnel has traditionally referred to the operators and maintainers who are employed in a system. Both roles have defined responsibilities. Both roles can have a significant effect on performance, reliability and safety. Users can also significantly affect performance. Users can easily be under-emphasized in studies because they can be comparatively harder to recruit and less predictable in their behaviors.

Procedures are the actions that need to be performed by either personnel or software.
Communication links allow for information to be transferred within a system and enable components to interact. All three classes of elements are considered to interact with each other. Their interaction produces a net result beyond the sum of the individual elements.

Figure 1.1 System elements and functions—the elements of a system are selected and configured to produce a result that is intended to satisfy its purpose and objectives. How each of the elements perform and interact with each other and with the total environment produces results at a certain level of performance. Evaluation is used to compare those results and the way that they are achieved with the system’s goals and objectives. Changes can be made to elements and their relationships in order to bring results into line with goals and objectives.

Source: Adapted from Christensen, J. (1985a)

Each system exists in a context that Christensen refers to as the ‘total environment.’ For example, the total environment for a highway transportation system includes the city in which it exists. Even though the highway may be well designed, elements in its total environment can have a significant effect on its performance. An individual who drops a cinder block from an overpass onto autos that are driving on an expressway produces an adverse effect on an otherwise well-designed ground transportation system. This is how the total environment can intrude into a system and, in this example, degrade its performance.

1.1.2 System definition

Czaja (1997:17–40) accounts for six approaches to system development: traditional, socio-technical, participatory, user-centered, computer-supported, and ecological interface design (EID).

1.1.2.1 TRADITIONAL

In the traditional approach, system elements are developed according to a four phase process:
concept, physical design, implementation and evaluation.

Sharit (1997:302–37) offers four ways to view such systems in order to better understand them: physical configuration, automation and workload, information flow, and partitioning techniques. Physical configuration considers the goals, agents and their connections, and timing constraints that affect information availability and reaction. The automation and workload view considers whether sufficient attention resources are available for the human to coordinate with an automated system. It also considers human attitudes toward automation and the consequences of error. Information flow considers the type, form, content, timing, rate and direction of information that is needed to realize system objectives, as well as channels through which it flows and the agents who must act on it. Partitioning techniques break a system apart into its logical subsystems, examine their relationships, and seek alternate ways to accomplish the same result more effectively. The human factors challenge in each of these instances is to account for the role of people in the system and the system’s effect on people.

Levis (1999:427–8) finds that the traditional approach can be effective when the requirements are well defined and remain essentially constant during the development period.
Complex system requirements typically change rapidly. The evolution of workplace studies over the 1990s has demonstrated that requirements can be complex and elusive.

Shortcomings in the traditional design model have led to difficulties. The traditional approach does not allow for requirements that change over time or new improvements in technology that become available. The traditional method’s failure to take the human element into account can result in heavy emphasis on hardware and software and ignorance of broader social, organizational and political issues. As a result, five alternative approaches to system design have been developed to improve on the traditional model.

1.1.2.2 SOCIO-TECHNICAL

Socio-technical system design emphasizes the fit between social and technical systems and the environment. Macroergonomics, which focuses on the relationship among humans, organizations, the environment and machines, follows a socio-technical approach.

1.1.2.3 PARTICIPATORY

In participatory design, individuals who are part of work groups and those who benefit from their product apply ergonomic principles and concepts to the design of a system. Participatory design has been applied to the design of products, work environments, and jobs.

1.1.2.4 USER-CENTERED

User-centered design considers both the human and the technical subsystems in the broader context. Users are typically consulted throughout the design process. The user-centered approach has been applied to product production, particularly in human–computer interaction.
Christensen’s model shown in Figure 1.1 includes the characteristics of a user-centered design.

1.1.2.5 COMPUTER-SUPPORTED

Computer software programs can be used to provide information retrieval, management and transformation in the development of complex technical systems.

1.1.2.6 ECOLOGICAL INTERFACE DESIGN (EID)

EID is a cognitive systems engineering approach that is used to analyze the work domain (through means-end analysis) and individual behavior traits. Jens Rasmussen’s (1983) skills-rules- knowledge hierarchy (which is described in Section 3.4.3) is used to determine how information is to be presented. The process offers system designers a set of maps to use in their analysis of operators and their work domain.

The way that a system is defined influences a research and development team’s approach to a project assignment. More often than not, the client will set the bounds for a research and development project. Even so, the team may be able to redefine the level of approach. In fact, redefinition of the level of approach or the focus of the problem can be a significant way to influence a project’s direction.

Abstraction hierarchy is one partitioning technique that is used to describe the system at several levels in order to separate the properties and functions of the system from its physical elements. Abstraction hierarchy can be used to perform functional analysis (Chapter 7). It can also be used to benefit the design ideation process. Instead of simply modifying an existing product or creating a new one, American design thinker Jay Doblin used abstraction hierarchy to create fewer artifacts through what he termed ‘denovation.’ Denovation is the practice of using the more abstract approach to a need to find a better way to fill it. The best solution might be no product at all. Such a shift in the level of approach sought a more effective solution opportunity by redefining the problem compared with its client’s original intention. ...

Indice dei contenuti

• Cover Page
• Title Page
• Copyright Page
• List of Illustrations
• Foreword
• Preface
• Acknowledgments
• Abbreviations
• Part I: Human Factors Practice
• Part II: Human Factors Methods
• Part III: Application
• Notes
• Appendix
• Bibliography