Human factors

Human factors
Research subject in a human fatigue study.

Human factors science or human factors technologies is a multidisciplinary field incorporating contributions from psychology, engineering, industrial design, statistics, operations research and anthropometry. It is a term that covers:

  • The science of understanding the properties of human capability (Human Factors Science).
  • The application of this understanding to the design, development and deployment of systems and services (Human Factors Engineering).
  • The art of ensuring successful application of Human Factors Engineering to a program (sometimes referred to as Human Factors Integration). It can also be called ergonomics.

In general, a human factor is a physical or cognitive property of an individual or social behavior which is specific to humans and influences functioning of technological systems as well as human-environment equilibriums.

In social interactions, the use of the term human factor stresses the social properties unique to or characteristic of humans.

Human factors involves the study of all aspects of the way humans relate to the world around them, with the aim of improving operational performance, safety, through life costs and/or adoption through improvement in the experience of the end user.

The terms human factors and ergonomics have only been widely used in recent times; the field's origin is in the design and use of aircraft during World War II to improve aviation safety. It was in reference to the psychologists and physiologists working at that time and the work that they were doing that the terms "applied psychology" and “ergonomics” were first coined. Work by Elias Porter, Ph.D. and others within the RAND Corporation after WWII extended these concepts. "As the thinking progressed, a new concept developed - that it was possible to view an organization such as an air-defense, man-machine system as a single organism and that it was possible to study the behavior of such an organism. It was the climate for a breakthrough."[1]

Specialisations within this field include cognitive ergonomics, usability, human computer/ human machine interaction, and user experience engineering. New terms are being generated all the time. For instance, “user trial engineer” may refer to a human factors professional who specialises in user trials. Although the names change, human factors professionals share an underlying vision that through application of an understanding of human factors the design of equipment, systems and working methods will be improved, directly affecting people’s lives for the better.

Human factors practitioners come from a variety of backgrounds, though predominantly they are psychologists (engineering, cognitive, perceptual, and experimental) and physiologists. Designers (industrial, interaction, and graphic), anthropologists, technical communication scholars and computer scientists also contribute. Though some practitioners enter the field of human factors from other disciplines, both M.S. and Ph.D. degrees in Human Factors Engineering are available from several universities worldwide. The Human Factors Research Group (HFRG) at the University of Nottingham provides human factors courses both at MSc and PhD level including a distance learning course in Applied Ergonomics. These courses are accredited by the Ergonomics Society.[2] Other Universities to offer postgraduate courses in human factors in the UK include Loughborough University and Cranfield University.


The Formal History of American Human Factors Engineering

The formal history describes activities in known chronological order. This can be divided into 5 markers:[3]

Developments prior to World War I

Prior to WWI the only test of human to machine compatibility was that of trial and error. If the human functioned with the machine, he was accepted, if not he was rejected. There was a significant change in the concern for humans during the American civil war. The US patent office was concerned whether the mass produced uniforms and new weapons could be used by the infantry men. The next development was when the American inventor Simon Lake tested submarine operators for psychological factors, followed by the scientific study of the worker. This was an effort dedicated to improve the efficiency of humans in the work place. These studies were designed by F W Taylor. The next step was the derivation of formal time and motion study from the studies of Frank Gilbreth, Sr. and Lillian Gilbreth.

Developments during World War I

With the onset of WWI, more sophisticated equipment was developed. The inability of the personnel to use such systems led to an increase in interest in human capability. Earlier the focus of aviation psychology was on the aviator himself. But as time progressed the focus shifted onto the aircraft, in particular, the design of controls and displays, the effects of altitude and environmental factors on the pilot. The war saw the emergence of aeromedical research and the need for testing and measurement methods. Still, the war did not create a Human Factors Engineering (HFE) discipline, as such. The reasons attributed to this are that technology was not very advanced at the time and America's involvement in the war only lasting for 18 months.[3]

Developments between World War I and World War II

This period saw relatively slow development in HFE. Although, studies on driver behaviour started gaining momentum during this period, as Henry Ford started providing millions of Americans with automobiles. Another major development during this period was the performance of aeromedical research. By the end of WWI, two aeronautical labs were established, one at Brooks Airforce Base, Texas and the other at Wright field outside of Dayton, Ohio. Many tests were conducted to determine which characteristic differentiated the successful pilots from the unsuccessful ones. During the early 1930s, Edwin Link developed the first flight simulator. The trend continued and more sophisticated simulators and test equipment were developed. Another significant development was in the civilian sector, where the effects of illumination on worker productivity were examined. This led to the identification of the Hawthorne Effect, which suggested that motivational factors could significantly influence human performance.[3]

Developments during World War II

With the onset of WW II, it was no longer possible to adopt the Tayloristic principle of matching individuals to preexisting jobs. Now the design of equipment had to take into account human limitations and take advantage of human capabilities. This change took time to come into place. There was a lot of research conducted to determine the human capabilities and limitations that had to be accomplished. A lot of this research took off where the aeromedical research between the wars had left off. An example of this is the study done by Fitts and Jones (1947), who studied the most effective configuration of control knobs to be used in aircraft cockpits. A lot of this research transcended into other equipment with the aim of making the controls and displays easier for the operators to use. After the war, the Army Air Force published 19 volumes summarizing what had been established from research during the war.[3]

Developments after World War II

In the initial 20 years after the WW II, most activities were done by the founding fathers: Alphonse Chapanis, Paul Fitts, and Small. The beginning of cold war led to a major expansion of Defense supported research laboratories. Also, a lot of labs established during the war started expanding. Most of the research following the war was military sponsored. Large sums of money were granted to universities to conduct research. The scope of the research also broadened from small equipments to entire workstations and systems. Concurrently, a lot of opportunities started opening up in the civilian industry. The focus shifted from research to participation through advice to engineers in the design of equipment. After 1965, the period saw a maturation of the discipline. The field has expanded with the development of the computer and computer applications.[3]

Founded in 1957, the Human Factors and Ergonomics Society is the world's largest organization of professionals devoted to the science of human factors and ergonomics. The Society's mission is to promote the discovery and exchange of knowledge concerning the characteristics of human beings that are applicable to the design of systems and devices of all kinds.[4]

The Cycle of Human Factors

Human Factors involves the study of factors and development of tools that facilitate the achievement of these goals. In the most general sense, the three goals of human factors are accomplished through several procedures in the human factors cycle,[citation needed] which depicts the human operator (brain and body) and the system with which he or she is interacting. First it is necessary to diagnose or identify the problems and deficiencies in the human-system interaction of an existing system. After defining the problems there are five different approaches that can be used in order to implement the solution. These are as follows:

  • Equipment Design: changes the nature of the physical equipment with which humans work.
  • Task Design: focuses more on changing what operators do than on changing the devices they use. This may involve assigning part or all of tasks to other workers or to automated components.
  • Environmental Design: implements changes, such as improved lighting, temperature control and reduced noise in the physical environment where the task is carried out.
  • Training the individuals: better preparing the worker for the conditions that he or she will encounter in the job environment by teaching and practicing the necessary physical or mental skills.
  • Selection of individuals: is a technique that recognizes the individual differences across humans in every physical and mental dimension that is relevant for good system performance. Such a performance can be optimized by selecting operators who possess the best profile of characteristics for the job.[citation needed]

Human Factors Science

Human factors are sets of human-specific physical, cognitive, or social properties which either may interact in a critical or dangerous manner with technological systems, the human natural environment, or human organizations, or they can be taken under consideration in the design of ergonomic human-user oriented equipment. The choice or identification of human factors usually depends on their possible negative or positive impact on the functioning of human-organizations and human-machine systems.

The human-machine model

The simple human-machine model is a person interacting with a machine in some kind of environment. The person and machine are both modeled as information-processing devices, each with inputs, central processing, and outputs. The inputs of a person are the senses (e.g., eyes, ears) and the outputs are effectors (e.g., hands, voice). The inputs of a machine are input control devices (e.g., keyboard, mouse) and the outputs are output display devices (e.g., screen, auditory alerts). The environment can be characterized physically (e.g., vibration, noise, zero-gravity), cognitively (e.g., time pressure, uncertainty, risk), and/or organizationally (e.g., organizational structure, job design). This provides a convenient way for organizing some of the major concerns of human engineering: the selection and design of machine displays and controls; the layout and design of workplaces; design for maintainability; and the design of the work environment.

Example: Driving an automobile is a familiar example of a simple man-machine system. In driving, the operator receives inputs from outside the vehicle (sounds and visual cues from traffic, obstructions, and signals) and from displays inside the vehicle (such as the speedometer, fuel indicator, and temperature gauge). The driver continually evaluates this information, decides on courses of action, and translates those decisions into actions upon the vehicle's controls—principally the accelerator, steering wheel, and brake. Finally, the driver is influenced by such environmental factors as noise, fumes, and temperature.

No matter how important it may be to match an individual operator to a machine, some of the most challenging and complex human problems arise in the design of large man-machine systems and in the integration of human operators into these systems. Examples of such large systems are a modern jet airliner, an automated post office, an industrial plant, a nuclear submarine, and a space vehicle launch and recovery system. In the design of such systems, human-factors engineers study, in addition to all the considerations previously mentioned, three factors: personnel, training, and operating procedures.

Personnel are trained; that is, they are given appropriate information and skills required to operate and maintain the system. System design includes the development of training techniques and programs and often extends to the design of training devices and training aids.

Instructions, operating procedures, and rules set forth the duties of each operator in a system and specify how the system is to function. Tailoring operating rules to the requirements of the system and the people in it contributes greatly to safe, orderly, and efficient operations.

Human Factors Engineering

Human Factors Engineering (HFE) is the discipline of applying what is known about human capabilities and limitations to the design of products, processes, systems, and work environments. It can be applied to the design of all systems having a human interface, including hardware and software. Its application to system design improves ease of use, system performance and reliability, and user satisfaction, while reducing operational errors, operator stress, training requirements, user fatigue, and product liability.

Human factors engineering focuses on how people interact with tasks, machines (or computers), and the environment with the consideration that humans have limitations and capabilities. Human factors engineers evaluate "Human to Human," "Human to Group," "Human to Organizational," and "Human to Machine (Computers)" interactions to better understand these interactions and to develop a framework for evaluation.

Human Factors engineering activities include: 1. Usability assurance 2. Determination of desired user profiles 3. Development of user documentation 4. Development of training programs.

Usability assurance

Usability assurance is an interdisciplinary concept, integrating system engineering with Human Factors engineering methodologies. Usability assurance is achieved through the system or service design, development, evaluation and deployment.

  • User interface design comprises physical (ergonomic) design, interaction design and layout design.
  • Usability development comprises integration of human factors in project planning and management, including system specification documents: requirements, design and testing.
  • Usability evaluation is a continuous process, starting with the operational requirements specification, through prototypes of the user interfaces, through usability alpha and beta testing, and through manual and automated feedback after the system has been deployed.

User Interface Design

Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them. This is a well known subject of Human Factors within the Engineering field. There are many different ways to determine human computer interaction at the user interface by usability testing.

Human Factors Evaluation Methods

Human Factors evaluation methods are part of Human Factors methodology, which is part of Human Factors Engineering.

Besides evaluation, Human Factors Engineering also deals with methods for usability assurance, for assessing desired user profiles, for developing user documentation and training programs, etc.

Until recently, methods used to evaluate human factors ranged from simple questionnaires to more complex and expensive usability labs.[5]

Recently, new methods were proposed, based on analysis of logs of the activity of the system users.

Actually, the work in usability labs and that of the new methods is part of Usability Engineering, which is part of Human Factors Engineering.

Brief Summary of Human Factors Evaluation Methods

Ethnographic analysis: Using methods derived from ethnography, this process focuses on observing the uses of technology in a practical environment. It is a qualitative and observational method that focuses on "real-world" experience and pressures, and the usage of technology or environments in the workplace. The process is best used early in the design process.[6]

Focus Groups: Focus groups are another form of qualitative research in which one individual will facilitate discussion and elicit opinions about the technology or process under investigation. This can be on a one to one interview basis, or in a group session. Can be used to gain a large quantity of deep qualitative data,[7] though due to the small sample size, can be subject to a higher degree of individual bias.[8] Can be used at any point in the design process, as it is largely dependent on the exact questions to be pursued, and the structure of the group. Can be extremely costly.

Iterative design: Also known as prototyping, the iterative design process seeks to involve users at several stages of design, in order to correct problems as they emerge. As prototypes emerge from the design process, these are subjected to other forms of analysis as outlined in this article, and the results are then taken and incorporated into the new design. Trends amongst users are analyzed, and products redesigned. This can become a costly process, and needs to be done as soon as possible in the design process before designs become too concrete.[6]

Meta-analysis: A supplementary technique used to examine a wide body of already existing data or literature in order to derive trends or form hypotheses in order to aid design decisions. As part of a literature survey, a meta-analysis can be performed in order to discern a collective trend from individual variables.[8]

Subjects-in-tandem: Two subjects are asked to work concurrently on a series of tasks while vocalizing their analytical observations. This is observed by the researcher, and can be used to discover usability difficulties. This process is usually recorded.

Surveys and Questionnaires: A commonly used technique outside of Human Factors as well, surveys and questionnaires have an advantage in that they can be administered to a large group of people for relatively low cost, enabling the researcher to gain a large amount of data. The validity of the data obtained is, however, always in question, as the questions must be written and interpreted correctly, and are, by definition, subjective. Those who actually respond are in effect self-selecting as well, widening the gap between the sample and the population further.[8]

Task analysis: A process with roots in activity theory, task analysis is a way of systematically describing human interaction with a system or process to understand how to match the demands of the system or process to human capabilities. The complexity of this process is generally proportional to the complexity of the task being analyzed, and so can vary in cost and time involvement. It is a qualitative and observational process. Best used early in the design process.[8]

Think aloud protocol: Also known as "concurrent verbal protocol", this is the process of asking a user to execute a series of tasks or use technology, while continuously verbalizing their thoughts so that a researcher can gain insights as to the users' analytical process. Can be useful for finding design flaws that do not affect task performance, but may have a negative cognitive affect on the user. Also useful for utilizing experts in order to better understand procedural knowledge of the task in question. Less expensive than focus groups, but tends to be more specific and subjective.[9]

User analysis: This process is based around designing for the attributes of the intended user or operator, establishing the characteristics that define them, creating a persona for the user. Best done at the outset of the design process, a user analysis will attempt to predict the most common users, and the characteristics that they would be assumed to have in common. This can be problematic if the design concept does not match the actual user, or if the identified are too vague to make clear design decisions from. This process is, however, usually quite inexpensive, and commonly used.[8]

"Wizard of Oz": This is a comparatively uncommon technique but has seen some use in mobile devices. Based upon the Wizard of Oz experiment, this technique involves an operator who remotely controls the operation of a device in order to imitate the response of an actual computer program. It has the advantage of producing a highly changeable set of reactions, but can be quite costly and difficult to undertake.

Problems with Human Factors Methods

Problems in how usability measures are employed include:
(1) measures of learning and retention of how to use an interface are rarely employed during methods and
(2) some studies treat measures of how users interact with interfaces as synonymous with quality-in-use, despite an unclear relation.[10]

Weakness of Usability Lab Testing

Although usability lab testing is believed to be the most influential evaluation method, it does have some limitations. These limitations include:
(1) Additional resources and time than other methods
(2) Usually only examines a fraction of the entire market segment
(3) Test scope is limited to the sample tasks chosen
(4) Long term ease-of-use problems are difficult to identify
(5) May reveal only a fraction of total problems
(6) Laboratory setting excludes factors that the operational environment places on the products usability

Weakness of Inspection Methods

Inspection methods (expert reviews and walkthroughs) can be accomplished quickly, without resources from outside the development team, and does not require the research expertise that usability tests need. However, inspection methods do have limitations, which include:
(1) Do not usually directly involve users
(2) Often do not involve developers
(3) Set up to determine problems and not solutions
(4) Do not foster innovation or creative solutions
(5) Not good at persuading developers to make product improvements

Weakness of Surveys, Interviews, and Focus Groups

These traditional human factors methods have been adapted, in many cases, to assess product usability. Even though there are several surveys that are tailored for usability and that have established validity in the field, these methods do have some limitations, which include:
(1) Reliability of all surveys is low with small sample sizes (10 or less)
(2) Interview lengths restricts use to a small sample size
(3) Use of focus groups for usability assessment has highly debated value
(4) All of these methods are highly dependent on the respondents

Weakness of Field Methods

Although field methods can be extremely useful because they are conducted in the users natural environment, they have some major limitations to consider. The limitations include:
(1) Usually take more time and resources than other methods
(2) Very high effort in planning, recruiting, and executing than other methods
(3) Much longer study periods and therefore requires much goodwill among the participants
(4) Studies are longitudinal in nature, therefore, attrition can become a problem.[11]

Application of Human Factors Engineering

An Example: Human Factors Engineering Applied to the Military

Before World War II, HFE had no significance in the design of machines. Consequently, many fatal human errors during the war were directly or indirectly related to the absence of comprehensive HFE analyses in the design and manufacturing process. One of the reasons for so many costly errors was the fact that the capabilities of the human were not clearly differentiated from those of the machine.

Furthermore, human performance capabilities, skill limitation, and response tendencies were not adequately considered in the designs of the new systems that were being produced so rapidly during the war. For example, pilots were often trained on one generation of aircraft, but by the time they got to the war zone, they were required to fly a newer model. The newer model was usually more complex than the older one and, even more detrimental, the controls may have had opposing functions assigned to them. Some aircraft required that the control stick be pulled back toward the pilot in order to pull the nose up. In other aircraft the exact opposite was required; namely, in order to ascend you would push the stick away from you. Needless to say, in an emergency situation many pilots became confused and performed the incorrect maneuver, with disastrous results.

Along the same line, pilots were subject to substitution errors due mostly to lack of uniformity of control design, inadequate separation of controls, or the lack of a coding system to help the pilot identify controls by the sense of touch alone. For example, in the early days of retractable landing gear, pilots often grabbed the wrong lever and mistakenly raised the landing gear instead of the flaps. Sensory overload also became a problem, especially in cockpit design. The 1950s brought a strong program of standardizing control shapes, locations and overload management.

The growth of human factors engineering during the mid- to late-forties was evidenced by the establishment of several organizations to conduct psychological research on equipment design. Toward the end of 1945, Paul Fitts established what came to be known as the Behavioral Sciences Laboratory at the Army Corps Aeromedical Laboratory in Dayton, Ohio. Around the same time, the U.S. Navy established the Naval Research Laboratory at Anacostia, Maryland (headed by Frank V. Taylor), and the Navy Special Devices Center at Port Washington, New York (headed by Leonard C. Mead). The Navy Electronics Laboratory in San Diego, California, was established about a year later with Arnold M. Small as head.

In addition to the establishment of these military organizations, the human factors discipline expanded within several civilian activities. Contract support was provided by the U.S. Navy and the U.S. Air Force for research at several noted universities, specifically Johns Hopkins, Tufts, Harvard, Maryland, Holyoke, and California (Berkeley). Paralleling this growth was the establishment of several private corporate ventures. Thus, as a direct result of the efforts of World War II, a new industry known as engineering psychology or human factors engineering was born.

Why is HFE important to the military?

Until today, many project managers and designers are still slow to consider Human Factors Engineering (HFE) as an essential and integral part of the design process. This is sometimes due to their lack of education on the purpose of HFE, in other instances it is due to others being perfectly capable of considering HFE related issues. Nevertheless, progress is being made as HFE is becoming more and more accepted and is now implemented in a wide variety of applications and processes. The U.S. military is particularly concerned with the implementation of HFE in every phase of the acquisition process of its systems and equipment. Just about every piece of gear, from a multi-billion dollar aircraft carrier to the boots that servicemen wear, goes at least in part through some HFE analyses before procurement and throughout its lifecycle.

Lessons learned in the aftermath of World War II prompted the U.S. War Department (now U.S. Department of Defense) to take some steps in improving safety in military operations. U.S. Department of Defense regulations require a comprehensive management and technical strategy for human systems integration (HSI)[12] be initiated early in the acquisition process to ensure that human performance is considered throughout the system design and development process.[13]

HFE applications in the U.S. Army

In the U.S. Army, the term MANPRINT is used as the program designed to implement HSI.[14][15] The program was established in 1984 with a primary objective to place the human element (functioning as individual, crew/team, unit and organization) on an equal footing with other design criteria such as hardware and software. The entry point of MANPRINT in the acquisition process is through requirements documents and studies.


MANPRINT (Manpower and Personnel Integration) is a comprehensive management and technical program that focuses attention on human capabilities and limitations throughout the system’s life cycle: concept development, test and evaluation, documentation, design, development, fielding, post-fielding, operation and modernization of systems. It was initiated in recognition of the fact that the human is an integral part of the total system. If the human part of the system can't perform efficiently, the entire system will function sub-optimally.

MANPRINT's goal is to optimize total system performance at acceptable cost and within human constraints. This is achieved by the continuous integration of seven human-related considerations (known as MANPRINT domains) with the hardware and software components of the total system and with each other, as appropriate. The seven MANPRINT domains are: Manpower (M), Personnel (P), Training (T), Human Factors Engineering (HFE), System Safety (SS), Health Hazards (HH), Soldier Survivability (SSv). They are each expounded on below:

Manpower (M)

Manpower addresses the number of military and civilian personnel required and potentially available to operate, maintain, sustain, and provide training for systems.[16] It is the number of personnel spaces (required or authorized positions) and available people (operating strength). It considers these requirements for peacetime, conflict, and low intensity operations. Current and projected constraints on the total size of the Army/organization/unit are also considered. The MANPRINT practitioner evaluates the manpower required and/or available to support a new system and subsequently considers these constraints to ensure that the human resource demands of the system do not exceed the projected supply.

Personnel (P)

Manpower and personnel are closely related. While manpower looks at numbers of spaces and people, the domain of personnel addresses the cognitive and physical characteristics and capabilities required to be able to train for, operate, maintain, and sustain materiel and information systems. Personnel capabilities are normally reflected as knowledge, skills, abilities, and other characteristics (KSAOs). The availability of personnel and their KSAOs should be identified early in the acquisition process and may result in specific thresholds. On most systems, emphasis is placed on enlisted personnel as the primary operators, maintainers, and supporters of the system. Personnel characteristics of enlisted personnel are easier to quantify since the Armed Services Vocational Aptitude Battery (ASVAB) is administered to potential enlistees.

While normally enlisted personnel are operators and maintainers; that is not always the case, especially in aviation systems. Early in the requirements determination process, identification of the target audience should be accomplished and used as a baseline for assessment. Cognitive and physical demands of the system should be assessed and compared to the projected supply. MANPRINT also takes into consideration personnel factors such as availability, recruitment, skill identifiers, promotion, and assignment.

Training (T)

Training is defined as the instruction or education, on-the-job, or self development training required to provide all personnel and units with their essential job skills, and knowledge. Training is required to bridge the gap between the target audiences' existing level of knowledge and that required to effectively operate, deploy/employ, maintain and support the system. The MANPRINT goal is to acquire systems that meet the Army's training thresholds for operation and maintenance. Key considerations include developing an affordable, effective and efficient training strategy (which addresses new equipment, training devices, institutional, sustainment, and unit collective tactical training); determining the resources required to implement it in support of fielding and the most efficient method for dissemination (contractor, distance learning, exportable packages, etc.); and evaluating the effectiveness of the training.

Training is particularly crucial in the acquisition and employment of a new system. New tasks may be introduced into a duty position; current processes may be significantly changed; existing job responsibilities may be redefined, shifted, or eliminated; and/or entirely new positions may be required. It is vital to consider the total training impact of the system on both the individuals and the organization as a whole.

Human Factors Engineering (HFE)

The goal of HFE is to maximize the ability of an individual or crew to operate and maintain a system at required levels by eliminating design-induced difficulty and error. Human factors engineers work with systems engineers to design and evaluate human-system interfaces to ensure they are compatible with the capabilities and limitations of the potential user population. HFE is conducted during all phases of system development, to include requirements specification, design and testing and evaluation. HFE activities during requirements specification include: evaluating predecessor systems and operator tasks; analyzing user needs; analyzing and allocating functions; and analyzing tasks and associated workload. During the design phase, HFE activities include: evaluating alternative designs through the use of equipment mockups and software prototypes; evaluating software by performing usability testing; refining analysis of tasks and workload; and using modeling tools such as human figure models to evaluate crew station and workplace design and operator procedures. During the testing and evaluation phase, HFE activities include: confirming the design meets HFE specification requirements; measuring operator task performance; and identifying any undesirable design or procedural features.

System Safety (SS)

System Safety is the design features and operating characteristics of a system that serve to minimize the potential for human or machine errors or failures that cause injurious accidents. Safety considerations should be applied in system acquisition to minimize the potential for accidental injury of personnel and mission failure.

Health Hazards (HH)

Health Hazards addresses the design features and operating characteristics of a system that create significant risks of bodily injury or death. Along with safety hazards, an assessment of health hazards is necessary to determine risk reduction or mitigation. The goal of the Health Hazard Assessment (HHA) is to incorporate biomedical knowledge and principles early in the design of a system to eliminate or control health hazards. Early application will eliminate costly system retrofits and training restrictions resulting in enhanced soldier-system performance, readiness and cost savings. HHA is closely related to occupational health and preventive medicine but gets its distinctive character from its emphasis on soldier-system interactions of military unique systems and operations.

Health Hazard categories include acoustic energy, biological substances, chemical substances, oxygen deficiency, radiation energy, shock, temperature extremes and humidity, trauma, vibration, and other hazards. Health hazards include those areas that could cause death, injury, illness, disability, or a reduction in job performance.

Organisational and Social

The seventh domain addresses the human factors issues associated with the socio-technical systems necessary for modern warfare. This domain has been recently added to investigate issues specific to Network Enabled Capability (NEC) also known as Network Centric Warfare (NCW). Elements such as dynamic command and control structures, data assimilation across mulitple platforms and its fusion into information easily understood by distributed operators are some of the issues investigated.

A soldier survivability domain was also proposed but this was never fully integrated into the MANPRINT model.

Domain Integration

Although each of the MANPRINT domains has been introduced separately, in practice they are often interrelated and tend to impact on one another. Changes in system design to correct a deficiency in one MANPRINT domain nearly always impact another domain.

Human Factors Integration

Areas of interest for human factors practitioners may include: training, staffing evaluation, communication, task analyses, functional requirements analyses and allocation, job descriptions and functions, procedures and procedure use, knowledge, skills, and abilities; organizational culture, human-machine interaction, workload on the human, fatigue, situational awareness, usability, user interface, learnability, attention, vigilance, human performance, human reliability, human-computer interaction, control and display design, stress, visualization of data, individual differences, aging, accessibility, safety, shift work, work in extreme environments including virtual environments, human error, and decision making.

Real World Applications of Human Factors - MultiModal Interfaces

Multi-Modal Interfaces

In many real world domains, ineffective communication occurs partially because of inappropriate and ineffective presentation of information. Many real world interfaces both allow user input and provide user output in a single modality (most often being either visual or auditory). This single modality presentation can often lead to data overload in that modality causing the user to become overwhelmed by information and cause him/her to overlook something. One way to address this issue is to use multi-modal interfaces.

Reasons to Use Multimodal Interfaces

  • Time Sharing – helps avoid overloading one single modality
  • Redundancy – providing the same information in two different modalities helps assure that the user will see the information
  • Allows for more diversity in users (blind can use tactile input; hearing impaired can use visual input and output)
  • Error Prevention – having multiple modalities allows the user to choose the most appropriate modality for each task (for example, spatial tasks are best done in a visual modality and would be much harder in an olfactory modality)

Examples of Well Known Multi-Modality Interfaces

  • Cell Phone – The average cell phone uses auditory, visual, and tactile output through use of a phone ringing, vibrating, and a visual display of caller ID.
  • ATM – Both auditory and visual outputs

Early Multi-Modal Interfaces by the Experts

  • Bolts “Put That There” – 1980 – used speech and manual pointing
  • Cohen and Oviatt’s “Quickset” – multi user speech and gesture input

Worker Safety and Health

One of the most prevalent types of work-related injuries are musculoskeletal disorders. Work-related musculoskeletal disorders (WRMDs) result in persistent pain, loss of functional capacity and work disability, but their initial diagnosis is difficult because they are mainly based on complaints of pain and other symptoms.[17] Every year 1.8 million U.S. workers experience WRMDs and nearly 600,000 of the injuries are serious enough to cause workers to miss work.[18] Certain jobs or work conditions cause a higher rate worker complaints of undue strain, localized fatigue, discomfort, or pain that does not go away after overnight rest. These types of jobs are often those involving activities such as repetitive and forceful exertions; frequent, heavy, or overhead lifts; awkward work positions; or use of vibrating equipment.[19] The Occupational Safety and Health Administration (OSHA) has found substantial evidence that ergonomics programs can cut workers' compensation costs, increase productivity and decrease employee turnover.[20] Therefore, it is important to gather data to identify jobs or work conditions that are most problematic, using sources such as injury and illness logs, medical records, and job analyses.[19]

Job analysis can be carried out using methods analysis, time studies, work sampling, or other established work measurement systems.

  • Methods Analysis is the process of studying the tasks a worker completes using a step-by-step investigation. Each task in broken down into smaller steps until each motion the worker performs is described. Doing so enables you to see exactly where repetitive or straining tasks occur.
  • Time studies determine the time required for a worker to complete each task. Time studies are often used to analyze cyclical jobs. They are considered “event based” studies because time measurements are triggered by the occurrence of predetermined events.[21]
  • Work Sampling is a method in which the job is sampled at random intervals to determine the proportion of total time spent on a particular task.[21] It provides insight into how often workers are performing tasks which might cause strain on their bodies.
  • Predetermined time systems are methods for analyzing the time spent by workers on a particular task. One of the most widely used predetermined time system is called Methods-Time-Measurement or MTM. Other common work measurement systems include MODAPTS and MOST.

See also


  1. ^ Porter, Elias H. (1964). Manpower Development: The System Training Concept. New York: Harper and Row, p. xiii.
  2. ^ Human Factors Research Group teaching webpage,
  3. ^ a b c d e The History of Human Factors and Ergonomics, David Meister
  4. ^ Human Factors and Ergonomics Society,
  5. ^ Stanton, N.; Salmon, P., Walker G., Baber, C., Jenkins, D. (2005). Human Factors Methods; A Practical Guide For Engineering and Design.. Aldershot, Hampshire: Ashgate Publishing Limited. ISBN 0754646610. 
  6. ^ a b Carrol, J.M. (1997). Human-Computer Interaction: Psychology as a Science of Design. Annu. Rev. Psyc., 48, 61-83.
  7. ^
  8. ^ a b c d e Wickens, C.D.; Lee J.D.; Liu Y.; Gorden Becker S.E. (1997). An Introduction to Human Factors Engineering, 2nd Edition. Prentice Hall. ISBN 0321012291.
  9. ^ Kuusela, H., Paul, P. (2000). A comparison of concurrent and retrospective verbal protocol analysis. The American Journal of Psychology, 113, 387-404.
  10. ^ Hornbaek, K (2006). Current Practice in Measuring Usability: Challenges to Usability Studies and Research, International Journal of Human-Computer Studies. 
  11. ^ Dumas, J. S.; Salzman, M.C. (2006). Reviews of Human Factors and Ergonomics. 2. Human Factors and Ergonomics Society. 
  12. ^ human systems integration (HSI)
  13. ^ DoD 5000.2-R (Paragraph 4.3.8)
  14. ^ MANPRINT website
  15. ^
  16. ^ Title 10, U. S. Code Armed Forces, Sec. 2434
  17. ^ Isabel A P Walsh; Jorge Oishi; Helenice J C Gil Coury (February 2008). "Clinical and functional aspects of work-related musculoskeletal disorders among active workers". Programa de Pós-graduação em Fisioterapia. Universidade Federal de São Carlos. São Carlos, SP, Brasil. Rev. Saúde Pública vol.42 no.1 São Paulo. 
  18. ^ Charles N. Jeffress (October 27, 2000). "BEACON Biodynamics and Ergonomics Symposium". University of Connecticut, Farmington, Conn.. 
  19. ^ a b "Workplace Ergonomics: NIOSH Provides Steps to Minimize Musculoskeletal Disorders". 2003. Retrieved 2008-04-23. 
  20. ^ Charles N. Jeffress (October 27, 2000). BEACON Biodynamics and Ergonomics Symposium. University of Connecticut, Farmington, Conn.. 
  21. ^ a b Thomas J. Armstrong (2007). Measurement and Design of Work. 

Additional reading

  • Meister, D. (1999). The History of Human Factors and Ergonomics. Mahwah, N.J.: Lawrence Erlbaum Associates. ISBN 0805827692. 
  • Oviatt, S. L.; Cohen, P. R. (2000, March). "Multimodal systems that process what comes naturally". Communications of the ACM (New York: ACM Press) 43 (3): 45–53. doi:10.1145/330534.330538. 
  • Sarter, N. B.; Cohen, P. R. (2002). "Multimodal information presentation in support of human-automation communication and coordination". Advances in Human Performance and Cognitive Engineering Research (Netherlands: JAI) 2: 13–36. doi:10.1016/S1479-3601(02)02004-0. 
  • Wickens, C.D.; Lee J.D.; Liu Y.; Gorden Becker S.E. (1997). An Introduction to Human Factors Engineering, 2nd Edition. Prentice Hall. ISBN 0321012291. 
  • Wickens, C. D.; Sandy, D. L.; Vidulich, M. (1983). "Compatibility and resource competition between modalities of input, central processing, and output". Human Factors (Santa Monica, CA, United States: Human Factors and Ergonomics Society) 25 (2): 227–248. ISSN 00187208. PMID 6862451. 

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