INDUSTRIAL ENGINEERING
2.3 Anthropometry
The term “anthropometry” from the Greek words anthropos (man) and metrein (to measure) explains how the physical dimensions of people vary (Konz and Johnson, 2004). Anthropometry is well defined by Sanders and McCormick (1992): measurement of the dimensions and certain other physical characteris- tics of the body such as volumes, centers of gravity, inertial properties, and masses of body segments.
When a task is given to a worker, there are two alternatives: selection or job modification. In selection, the worker is selected from the population of workers based on criteria such as strength, height, weight, age, or even gender. This selection strategy has been called fitting the man to the task. The other alterna- tive is to modify the job so that almost anyone can do it. This job modification is called fitting the task to the man. Job modification has been widely implemented since the Americans with Disabilities Act (ADA)
TABLE 2.1 The History of Human Factors and Important Activities
Period Notable Activities
Prehistory to eighteenth Century ● Prehistoric period
Beginning of HF: the first man-made tool
● 1950 to 1900 BC
Realistic description of work conditions in different professions, probably from Egypt’s Middle Kingdom
● 960 AD: commonsense ergonomics
The Danish king, Harald Bluetooth, built four armed bases having symmetrical barracks
However, the exits from the barracks into the passageways between them broke the symmetry such that none of the exits was directly opposite any other exit
It appears that the architect wanted to prevent collisions between soldiers who were running out of two barracks at the same time
The displacement of the exits is a sign that some ergonomic thinking was applied
● 1759 AD: comparative test
Danish proprietor, Borreschmith, introduced a new plough
He understood the concept of ergonomics. The new plough was tested under realistic conditions and it came with a set of user instructions
Nineteenth Century to World War II ● 1887: ergonomics with scientific base
The Danish government wanted to limit the amount of color added to margarine
The only question was where to set a limit to ensure that margarine was visibly different from butter
Alfred Lehmann published an article describing the human ability to discriminate among different colors, and designed a series of color cards showing different shades of yellow as a reference to the colors of margarine. The color tables came with detailed instructions
● Early 1900s: real start of HF
Frank and Lillian Gilbreth began the first motion study
Their work included the study of skilled performance and fatigue, the design of workstations and equipment for the handicapped, and the analysis of hospital surgical teams
● World War II: fitting the person to the job
The major emphasis of behavioral scientists was on the use of tests for selecting the proper people for jobs and on the development of improved training procedures
During World War II, however, it became clear that even with the best selection and training, the operation of some of the complex equipment still exceeded the capabilities of the people who had to operate it
1945 to 1960 ● The HF profession was born; HF study in the United States was essentially concentrated in the military-industrial complex
● At the end of the war in 1945, engineering psychology laboratories were established in the United States and Britain. In 1949, the Ergonomics Research Society was formed in Britain, and the first book on HF was published
● In 1957, the journal Ergonomics from the Ergonomics Research Society appeared; the Human Factors Society was formed. Russia launched Sputnik and the race for space was on
● In 1959, the International Ergonomics Association was formed
continued
of 1990, which took effect in 1992. Since then, industries have incorporated this fitting the task to the man concept in consumer product designs.
Table 2.2 shows useful dimensions that apply to the particular postures needed for workplace design for adult males and females in the United States. Some of these data have been incorporated into man- nequins that can be manipulated, or computer programs that enable product designers to simulate prod- uct usability at the planning stage of the design.
TABLE 2.1 (Continued)
Period Notable Activities
1960 to 1980 ● Rapid growth and expansion of HF
● Human Factors in the United States expanded beyond military and space applications
● With the race for space and manned space flights, HF quickly became an important part of the space program
● Human Factors considerations were incorporated into many industries, including those dealing in pharmaceuticals, computers, automobiles, and other consumer products
● Industry began to recognize the importance and contribution of HF for both the design of workplaces and the products manufactured there 1980 to 1990 ● Computer technology provided new challenges for the HF profession
New control devices, information presentation via computer screen, and the impact of new technology on people were new areas for the HF profession
● Several disasters related to HF:
The incidents at Three Mile Island nuclear power station in 1979. The incident came very close to resulting in a nuclear meltdown
In 1984, a leak of methylisocyanate (MIC) at the Union
Carbide pesticide plant in Bhopal, India, claimed the lives of nearly 4000 people and injured another 200,000
In 1986, an explosion and fire at the Chernobyl nuclear power station in Soviet Union resulted in more than 300 dead, widespread human exposure to harmful radiation, and millions of acres of radioactive contamination
Three years later, in 1989, an explosion ripped through a Phillips Petroleum plant in Texas. It killed 23 people, injured another 100 workers, and resulted in the largest single U.S. business insurance loss in history ($1.5 billion)
● Human Factors involvement increased dramatically in forensics and particularly product liability and personal injury litigations 1990 and beyond ● Intensive involvement of HF study in building a permanent
space station
● HCI: computers and the application of computer technology
● Safety
Workplace safety: the U.S. Occupational Safety and Health Administration (OSHA) regulations
Aviation safety: the Federal Aviation Administration (FAA) expands its HF research efforts
● Medicine
The design of medical devices
The design of products and facilities for the elderly
● Security
Human interaction with security technology
Intelligence analysis
Sources : Strom G., Ergon. Des., 11, 5–6, 2003; Sanders, M.S. and McCormick, E.J., Human Factors in Engineering and Design (7th ed.), McGraw-Hill, Singapore, 1992.
TABLE 2.2 Selected U.S. Civilian Body Dimensions (in cm with Bare Feet; add 3 cm to Correct for Shoes) of Industrial Relevance
Body Dimensions
Female Male
5th 50th 95th 5th 50th 95th
Standing
1. Tibial height 38.1 52.0 46.0 41.0 45.6 50.2
2. Knuckle height 64.3 70.2 75.9 69.8 75.4 80.4
3. Elbow height 93.6 101.9 108.8 100.0 709.9 119.0
4. Shoulder (acromion) height 121.1 131.1 141.9 132.3 142.8 152.4
5. Stature 149.5 160.5 171.3 161.8 173.6 184.4
6. Functional overhead reach 185.0 199.2 213.4 195.6 209.6 223.6
Sitting
7. Functional forward reach 64.0 71.0 79.0 76.3 82.5 88.3
8. Buttock-knee depth 51.8 56.9 62.5 54.0 59.4 64.2
9. Buttock-popliteal depth 43.0 48.1 53.5 44.2 49.5 54.8
10. Popliteal height 35.5 39.8 44.3 39.2 44.2 48.8
11. Thigh clearance 10.6 13.7 17.5 11.4 14.4 17.7
12. Sitting elbow height 18.1 23.3 28.1 19.0 24.3 29.4
13. Sitting eye height 67.5 73.7 78.5 72.69 78.6 84.4
14. Sitting height 78.2 85.0 90.7 84.2 90.6 96.7
15. Hip breadth 31.2 36.4 43.7 30.8 35.4 40.6
16. Elbow-to-elbow breadth 31.5 38.4 49.1 35.0 41.7 50.6
Other dimensions
17. Grip breadth, inside diameter 4.0 4.3 4.6 4.2 4.8 5.2
18. Interpupillary distance 5.1 5.8 6.5 5.5 6.2 6.8
Source : Helander, 1995.
18
6
7
14
17 15 16 13
1112
10
8 9 5
4 3 2 1
There are three design principles when designing for most individuals: design for extremes, design for the average, and design for adjustability (Niebel and Freivalds, 2003). Design for extremes implies that a specific design feature is a limiting factor in determining either the maximum or minimum value of a population variable that will be accommodated. For example, reach distances should be designed for the minimum individual, that is, a 5th percentile female arm length. Then, 95% of all females and almost all males will be able to reach. On the other hand, clearances, such as the height of an entry opening to a storage room, should be designed for the maximum individual, that is, a 95th percentile male stature, so that 95% of all males and almost all females will be able to enter the opening.
Design for the average is the cheapest but least preferred approach. Even though there is no individual with all average dimensions, there are certain situations where it would be impractical or too costly to include adjustability for all features. For example, most office desks have fixed dimensions and the design for extreme principle is not appropriate in this case. Therefore, the desk height is determined at the 50th percentile of the elbow height for the combined female and male populations (roughly the average of the male and female 50th percentile values) so that most individuals will not be unduly inconvenienced.
However, the exceptionally tall male or very short female may experience some postural discomfort.
Design for adjustability is typically used for equipment or facilities that can be adjusted to fit a wide range of individuals. Chairs, vehicle seats, steering columns, and tool supports are devices that are typi- cally adjusted to accommodate the worker population ranging from 5th percentile females to 95th per- centile males. Obviously, designing for adjustability is the preferred method of design, but there is a trade-off with the cost of implementation.