tzippy@dasys1.uucp (Tzipporah BenAvraham) (06/05/90)
Index Number: 8658
John here is another file for you.. hope it helps
it is called 30-some.asc by Greg Vanderheiden
Thirty Something (Million): Should They Be Exceptions?
GREGG C. VANDERHEIDEN1, Trace Research and Development
Center, Waisman Center and Department of Industrial
Engineering, University of Wisconsin-Madison
There are over thirty million people in the U.S. with
disabilities or functional limitations (of which a major cause is
aging), and this number is increasing. An examination of the role
of human factors in addressing this population is presented which
would include both special designs for disability/aging and the
incorporation of disability/aging into mainstream human factors
research and education. Statistics regarding the size and
characteristics of this population are presented, including the
costs of disability. Examples demonstrating the economic and
commercial feasibility of incorporating disability/aging
considerations in mass market designs are provided along with a
discussion of the benefits to non-disabled users.
Requests for reprints should be sent to Gregg C. Vanderheiden,
Trace R&D Center, University of Wisconsin-Madison, 1500 Highland
Avenue, Madison, WI 53705.
RUNNING TITLE: Thirty-Something (Million)
KEY WORDS: disability, aging, design, accommodation
INTRODUCTION
As a nation we are beginning to be more aware of the large numbers
of persons with disabilities and the problems they face. This
group includes those born with disabilities and those whose
abilities diminish during their lifetime through disease, accident
or aging. Recent Federal legislation, primarily Section 508 of
Public Law 99-506 and the pending Americans with Disabilities Act,
addresses accessibility problems faced by persons with disabilities
in the workplace and community. In addition, the demographic trend
toward a growing elderly population (particularly as the "baby
boom" generation ages) is raising the prospect of a large number of
consumers with decreasing abilities. The serious impact this will
have on mass market products is beginning to be recognized by
manufacturers.
These developments have sparked increased discussion within the
human factors community. There is little question that human
factors research and principles can be a benefit to those who are
designing special devices for persons with functional limitations.
However, the open question is, "Should the mainstream design of
products include consideration of people who have disabilities or
are elderly?" (In other words, should mass market products be made
more accessible via their initial design?)
It is easy to answer this question in the affirmative from a
humanitarian standpoint, yet this is likely to represent a major
change in scope for the human factors field. The specific role of
human factors with regard to design for disability/aging is yet to
be determined. Such a change must also be well considered in terms
of effects on personnel, curricula and economic perspectives.
It is useful to break this complex question into the
following component questions:
-- Who is included in the category of "disabled and
elderly persons"?
-- How large is the disabled and elderly population?
-- Can't the needs of disabled or elderly persons be
handled separately or as exceptions?
-- What can the human factors field do for this group?
-- Is it economically and practically feasible to
include disabled and elderly persons in the design
process for mass market products?
-- What are the "benefits" of incorporating disability
and aging considerations into mainstream human
factors activities?
-- What are the "costs"?
Who Is Included in the Category of "Disabled and Elderly Persons"?
It is important to understand that there is no clear line between
people who are categorized as "disabled" and those who are not. A
performance or ability distribution is single-peaked, as in the
hypothetical distribution in Figure 1, rather than bimodal with
distinctive 'able' and 'disabled' groups. This distribution
includes a small number of individuals who have exceptionally high
ability, a larger number of individuals with mid-range ability, and
another longer tail representing individuals with little or no
ability in that particular area. In looking at such a
distribution, it is impossible to simply draw a vertical line and
separate able-bodied from disabled persons. It is also important
to note that each aspect of ability has a separate distribution.
Thus, a person who is poor along an ability distribution in one
dimension (e.g., vision) may be at the other end of the
distribution (i.e., excellent) with regard to another dimension
(e.g., hearing or IQ). Thus, individuals do not fall at the lower
or upper end of the distribution overall, but generally fall into
different positions depending upon the particular ability being
measured.
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INSERT FIGURE 1 ABOUT HERE
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The 95th Percentile Illusion
It should be clear that even if elderly and disabled persons are
included in the mainstream design process, it is not possible to
design all products and devices so that they are usable by all
individuals. There will always be a "tail" of individuals who are
unable to use a given product.
In order to include a sizeable portion of the population in the
category of "those who can use a product with little or no
difficulty," the 95th percentile (or similar percentile) design
rule is often used. The problem is, however, that there are no
"95th percentile" data for specific designs. Rather, there are
only data with regard to individual physical or sensory
characteristics. Thus there is 95th percentile data for height, a
95th percentile for vision, hearing, etc. As a result, it is not
possible to determine when a product can be used by 95% of the
people. It is only possible to estimate when a product can be used
by 95% of the population along any one dimension. Since people in
the 5% tail for any one dimension (e.g., height) are usually not
the same people as the 5% tail along another dimension (e.g.,
vision) it is possible to design a product using 95th percentile
data and end up with a product that can be used by far less than
95% of the population.
Figure 2 shows a simple illustration of this phenomenon. In
the figure is a population of ten individuals who appear to
be very similar. Upon closer examination however you will
find that 10% of them (1 of 10) have one short leg, 10% have
a visual impairment, 10% have a missing arm, 10% are short
and 10% cannot hear.
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INSERT FIGURE 2 HERE
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Let us assume that these ten people represent a mini-population.
Further, let's assume that we design a product that required 90th
percentile ability along each of the dimensions of height, vision,
leg use, arm use, and hearing. In this instance we would end up
with a product which was in fact only usable by 50% of this
population. This occurs because, although only 10% of this
mini-population is limited in any single dimension, different
individuals fall into the 10% tail for each dimension and only 50%
of the population is within 90th percentile for all 5 areas.
In real life, the effect is not quite this dramatic, and its
calculation is not so simple. First of all, the percentage of
individual with disabilities is less than 10% along any one
dimension. Secondly, there is often overlap where one individual
would have more than one disability (elderly individuals, for
example).
On the other hand, there is also a very wide range of different
individual types of disability. In addition, the data from which
the 95th percentiles are calculated often exclude persons with
disabilities, making the percentage who could use the design(s)
smaller than one would first calculate.
How Large is the Disabled and Elderly Population?
Determining the exact number of individuals with disabilities or
with limitations due to aging is difficult. Estimates vary
depending upon the definitions of disability used and the sources
of the data. There is also a substantial number of individuals
with disabilities who have returned to the work force despite
significant functional limitations2 and who therefore do not
consider themselves disabled. Their functional limitations,
however, must be taken into account when they are trying to perform
within an environment of facilities and tools designed for "normal"
or 95th percentile function.
To further confuse efforts to understand the makeup of this segment
of our population, most of the data reported overlap. That is, the
same individual may be counted in both the visually impaired and
hearing impaired segments. Adding the two numbers together would
give a false reading of the size of the "visual or hearing
impaired" population. For example, in one study the following
incidence numbers are reported (based on data from National Center
for Health Statistics, 1979, as reported in Czajka, 1984):
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INSERT TABLE 1 HERE
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If you add the numbers in column 1 of Table 1 together, you get
121% of the population (all ages). Adding column 2 gives you 236%
(of the 65+ population). Clearly these numbers are not exclusive
of each other. It is therefore important to differentiate
incidence figures for single types of impairment from "total
person" counts. In the latter case one must be sure they are using
mutually exclusive figures before doing any adding. It is also
important to note from this that most individuals will have
multiple impairments, and solutions targeted at a single disability
may not be useful to them.
Finally, it is important to distinguish between the number of
people that have an impairment and the number with a functional
limitation. Impairment is a function of the basic capabilities (or
lack thereof) of the individuals themselves. Functional limitation
is a reflection of the interaction between these impairments and
the design (physical, social, etc.) of the world around them.
Safer designs might somewhat reduce the number of injuries and
therefore the impairment figures. The greater potential for
reducing these figures, however, is in reducing the number of
people with functional limitations through better design of
products, environments and systems. In this paper, both impairment
and functional limitation figures are presented. In each case they
are labeled as impairment or limitation as well as being single
dimensional (overlapping) or non-duplicative.
Though individual estimates may vary, it appears that there are
over thirty million people in the United States who are disabled or
have functional limitations due to injury, illness or aging (Kraus
& Stoddard, 1989). This is something between 12% and 20% of the
population. Many of these individuals also have multiple
disabilities.
Although this is a large number, it should be noted that the types
and degree of impairment vary widely. Figure 3 shows a breakdown
of just the "impairments" data from the 1979 National Health
Interview Survey (NHIS). (Numbers within the chart are
non-duplicative; however, these individuals may have respiratory,
circulatory or other conditions as well.) Because of the diversity
of disabilities, the number of individuals with any one particular
type or combination of disabilities is much smaller. This makes it
more difficult to accommodate this population in the overall design
process because of the many dimensions which would need to be
considered. The fact that the size of any of these individual
populations is quite small (less than 5%) also helps explain how
such a large portion of the population can be left out even while
designing for the 95th percentile along single dimensions.
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INSERT FIGURE 3 ABOUT HERE
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Figures 4 and 5 provide two different profiles of the population
with disabilities. For younger people (Figure 4), some of the
"classic" types of disabilities (e.g., deafness or blindness) are
quite small, while other less easily identified disabilities (e.g.,
learning disabilities) represent a large portion of the
population. Since many of the larger disability groups cannot be
addressed directly through physical design, it may appear that the
problem is smaller than first thought. Even the small percentages,
however, represent fairly large numbers (i.e., millions) of
individuals.
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INSERT FIGURE 4 ABOUT HERE
INSERT FIGURE 5 ABOUT HERE
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Probably the most sobering statistics, however, are those shown in
Figures 6 and 7, dealing with aging. For those of us who survive
to age 65, we find that the number who have functional limitations
will leap up to 45%. For those of us who survive to age 75 or
more, the percentage jumps to a staggering 72.5%. This is
particularly important since medical advancements are increasing
the life expectancy, making it more probable that we will reach
this age. Figure 7 provides a forecast of the aging population
over the next 60 years. As can be seen the portion of our
population that is over 55 grows steadily and is predicted to reach
35% of the population by the year 2050.
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INSERT FIGURE 6 ABOUT HERE
INSERT FIGURE 7 ABOUT HERE
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As we look at older populations we also see a shift in the relative
percentage of individuals with different types of disabilities.
Comparing figures 4 and 5, we can see that, although visual and
hearing impairments are relatively rare in the younger population,
they increase sharply as we age, dwarfing the major disability
categories of youth (learning disabilities, mental retardation,
speech impairments). Given the current demographic trends,
including the ability of modern medicine to extend the life span,
it is clear that an ever-increasing portion of our population (at
least for the foreseeable future) is going to be experiencing
functional limitations of some sort.
It is interesting to note that the disabled community refers to
those without disabilities as "TAB's," or the Temporarily
Able-Bodied. All of us are aging and most of us hope to live to be
elderly. If we make it, most of us can look forward to
experiencing some type of functional limitations sufficient to make
operation of the products in our environment (as they are now
designed) more difficult or impossible for us to use. This
transition from able-bodied to disabled is a gradual, continuous
process. Thus, design for the mainstream that considers the needs
of an aging, and decreasingly able-bodied population, appears
particularly worthwhile.
Can't the Needs of Disabled and Elderly Persons Be Handled
Separately or As Exceptions?
Although the total number of elderly or disabled persons is large,
each individual disability or impairment area represents only a
small portion of the population. We are therefore not dealing with
one large group of people but with many small groups which together
represent a major portion of our population. This raises a question
as to the most effective means of addressing these problems. Is it
better to design everything so that it is accessible to most
persons, including those with disabilities? Or is it more
effective to design for the able bodied population and create
special designs for persons with specific types of disability?
First we must start with the understanding that it is impractical,
if not impossible, to design everything so that it is accessible by
everyone regardless of their limitations. Some things have
inherently limited usefulness to some populations (e.g., a stereo
system for deaf individuals, or a kaleidoscope for blind persons).
There are also combinations of impairments which would make
adaptation difficult to do on a standard basis (e.g. a deaf-
blind-aphasic individual). However, for most types or degrees of
impairment there are simple and low cost (or no cost) adaptations
to product design which can significantly increase their
accessibility and usefulness to individuals with functional
impairments. In these cases, inclusion of the design feature or
approach in the standard product can be of substantial benefit to
the individual and society as a whole (see further discussion in
next section).
Another argument for incorporating accessibility directly into the
design of mass market goods stems from the population distribution
characteristics of elderly and disabled persons. As shown above,
the number of persons with disabilities overall is large, but those
with specific types of impairment represent a small portion of the
total population. These small groups are further divided by the
degree of limitation. People with mild hearing loss, for example,
would use different techniques and aids from those with severe
hearing loss. Thus, the target users are too small to be addressed
individually. They are also geographically distributed across the
U.S. As a result it is both economically impractical and a
marketing and support nightmare to design individual appliances
(stoves, microwave ovens, mixers, vacuum cleaners, cars, etc.) for
each population. Finally, due to aging and other causes, we all
are at risk of having to operate our appliances with diminishing
functional capabilities over time.
We are therefore left with a balancing act. It is unreasonable to
design everything so that it can be used by everyone. It is
equally unreasonable to produce special designs for each major
consumer product to accommodate the different disability groups.
Some special aids and other devices will continue to be necessary
to fulfill those needs that accessible mass market design cannot
effectively meet. But where mass market goods can easily be made
more accessible through careful and informed design it appears to
be the best and most economical approach.
What Can the Human Factors Field Do For This Group?
As human factors researchers, we haven't been directing any
significant effort toward the needs of the disabled and elderly
population even though they comprise a large portion of the general
population. For example, only a small percentage of the papers in
the Human Factors Journal have dealt with disability and aging
issues. Disabilities and functional limitations of aging are only
peripherally mentioned in our textbooks and handbooks and rarely
included in our data tables. Courses on disability or aging in
human factors curricula are rare and usually take the form of
special topic seminars. Little or no attention is paid in the
standard curriculum to the needs, characteristics or design
considerations to accommodate persons with reduced or diminishing
functional abilities.
This lack of focus on those with functional limitations is not
because our skills are not applicable to their problems. It also
does not appear to be a direct function of insensitivity, although
there is room for improvement there. Rather, it seems mostly to be
a lack of awareness and a lack of basic knowledge and skills needed
to work and teach in this area. It would require that we master a
much broader range of information than we currently are familiar
with. It would also require the development of new areas of
knowledge, including the types, degrees and implications of
disabilities and functional limitations, the demographics for these
populations, the psychological and economic aspects of disability,
and specific strategies for increasing usability of designs by
persons experiencing limitations.
Is It Economically and Practically Feasible to Include Disabled and
Elderly Persons in the Design Process for Mass Market Products?
Experience so far has shown that consideration of disabilities and
functional limitations in mainstream design is very definitely
feasible from both an economic and practical standpoint. In the
majority of cases, accessibility can be added to a product's design
for little or no cost.
For example, Apple Computer has incorporated several special
features directly into their standard operating system to
accommodate individuals with varying disabilities. One feature,
called "Sticky Keys," allows individuals who only have one hand
available or who use a head or mouth stick to operate the standard
keyboard. Ordinarily, a person typing with a single finger or
stick cannot use a keyboard, since it requires that you hold down
two or more keys simultaneously for some operations (e.g.,
control-g or alt-h). The "sticky keys" feature allows the person
to type the keys sequentially rather than concurrently. It is
activated by tapping five times on the shift key and deactivates
should any two keys be depressed simultaneously (as a normal typist
would). Thus, the feature is transparent to those users who don't
need it.
Another feature now standard on Macintosh computers is called
"mousekeys." Individuals who do not have the motor control
necessary to operate a mouse can use the mousekeys feature to
control the mouse cursor on the screen by using the keys on the
numeric keypad. A third feature is "CloseView," which allows
individuals to zoom the screen image up to 16 times its normal
size. Thus visually impaired individuals may use the computer
without special add-on devices.
All of the above features have been standard on all Macintosh
computers for the past two years. Once the features were
developed, the cost to include them in the product is essentially
zero. The Sticky Keys and Mouse Keys features take up just 4k of
space on the disk and are included in every system shipped. The
CloseView feature is just 20k and is included in the package of
system disks shipped with each computer. Even when these same
features had to be incorporated directly in the hardware (as they
did for the Apple IIGS), the manufacturing cost was negligible
(since it simply changed the code in the microcontrollers for the
keyboard). Although Apple Computer has taken the early lead in
this area, other major computer manufacturers and operating system
developers have similar features in the works.
Another example of no-cost accommodations can be found on some mass
market mixing bowls. These bowls have small braille legends cast
onto the underside of the bowl, listing the capacity in braille.
Other than a few seconds to cut the dimples into the original mold,
there is no additional cost involved in making the bowls. Some
microwave manufacturers also offer braille/tactile overlays for
their control panels to facilitate their use by blind or visually
impaired users. US Sprint has braille version of its FONE cards.
Accessible Design Can Sometimes Decrease Costs: In some cases,
creating a design which is more accessible can in fact decrease the
costs involved in manufacture or maintenance/support of a product.
One example is to be found in elevator design. Individuals in
wheelchairs or on crutches had great difficulty with the large
"banks" of elevators present in many buildings. Often the elevator
door would open, but before the person in a wheelchair could get to
the correct elevator, the door would close. An obvious solution
would be for the elevators to stay open for a longer period of
time. However, building codes required that a building's floors be
visited by the elevators with a specified frequency. If the doors
were made to stand open longer, additional elevators would need to
be installed in the building to meet the level of service
standards. In a building like the Sears Tower, this could result
in a substantial portion of the building being consumed by
elevators.
On examining the problem more carefully, however, it was noted that
the problem was not that individuals in wheelchairs or on crutches
were unable to enter an elevator within the time the door normally
remained open. The problem was knowing which elevator was coming
so they could position themselves in front of its door. By simply
reprogramming the elevator's controlling computer it was possible
to have the elevator activate the signal tone and light for the
proper elevator in advance of its arrival at the floor.
Adopting this advance warning as a standard for elevators solves
the accessibility problem without increasing costs. In addition it
was found that both disabled and able-bodied persons are able to
board the elevator much more rapidly when this advance warning is
given. As a result, it was then possible to either decrease the
number of elevators and still provide the same level of service to
the floors, or to increase the level of service, since the time the
elevator is open on a floor could be reduced. Thus, the more
accessible design also turned out to be less expensive overall.
Disability Design Can Increase the Functionality for Able-Bodied
Users: It is very common for accessible designs to also prove
beneficial for individuals who do not have limitations (Newell,
1986). In the elevator example above, the advance warning not only
increased the speed with which the elevators could service the
floors, but also made it much easier for normal passengers to
maneuver their luggage and board the elevator (i.e., without
having to grab one bag and throw it into the elevator door while
they retrieved their other bags from in front of the wrong
elevator).
Probably the most common example of accessible design is the curb
cut. Although the curb cuts are put in for persons in wheelchairs,
it is estimated that for every individual in a wheelchair using a
curb cut, somewhere between ten and one hundred bicycles,
skateboards, shopping carts, baby carriages and delivery carts use
the curb cut. It is also not uncommon to see individuals walk
slightly out of their path in order to walk up a curb cut rather
than stepping up onto the curb, indicating a preference for the
curb cut even when walking.
The "mouse keys" feature on the Macintosh computer provides another
example. In addition to allowing the user to move the cursor
across the screen, the mouse keys also have a "one pixel" feature.
Tapping specific keys on the numeric keypad causes the mouse to
move one pixel in the corresponding direction. As a result, it is
possible to very precisely position the mouse on the screen. Since
the normal mouse continues to be active at all times, it is
possible for an able-bodied individual to use the regular mouse for
general pointing movements and to move the mouse into the
approximate area of interest. They can then reach over and tap on
the numeric keypad keys (with mouse keys activated) in order to
nudge the cursor the exact number of pixels required for precise
positioning. Thus, the mouse keys feature adds functionality and a
precision of movement which was not previously available to
able-bodied users.
A real-time Palentype (similar to stenotype in U.S.) translation
aid was developed in England to allow a deaf member of Parliament
to follow floor debates more easily and precisely. It later found
its way into the courtroom for lawyers who could hear normally but
wanted transcripts of the day's trial (Newell & Cairns, 1987).
In general, when products, environments or systems are made more
accessible to persons with limitations, they are usually easier for
more able-bodied persons to use. Some of the potential benefits
include lower fatigue, increased speed and lower error rates.
The Consequences of Not Providing Accessible Designs: The benefits
above are only half of the economic justification for more
accessible design. A second and perhaps more significant economic
benefit would be reduction of the costs to society which result
from individuals being unable to effectively function independently
in the world as it is currently designed. These costs take the
form of benefits paid out of tax dollars for special assistance due
to a disabled person's unemployment or non-independent living. In
addition, there is the loss to society of these individuals'
productivity (meaning loss of tax revenues, creation of wealth,
contributions to society).
Overall disability outlays rose approximately linearly from $50
billion in 1975 to $170 billion in 1986 (Berkowitz & Greene,
1989). Assuming this trend continues, the outlays for 1990 are
estimated to exceed $200 billion. (See Figure 8.) Approximately
half of the 1986 cost was for medical treatment, while the other
half was for direct transfer payments. (Transfer payments are the
actual funds allocated each year to people because of
disabilities.) Other economic losses from disability (not
including transfer payments) are estimated to have been in excess
of $177 billion in 1980 (Chirikos, 1989) (equivalent to $290
billion in 1990 dollars).
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INSERT FIGURE 8 ABOUT HERE
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Approximately one-third of the persons with disabilities who can
and would like to work are unemployed. This amounts to
approximately two million people (Kraus & Stoddard, 1989).
Figuring an average annual salary of $15,000, that amounts to $30
billion in lost productivity, as well as several billion dollars in
lost tax revenues. This is in addition to the large costs in the
form of transfer payments to those individuals who cannot live
independently.
What Are the "Benefits" of Incorporating Disability and Aging
Considerations into Mainstream Human Factors Activities?
As we have seen, considering those with functional limitations in
the overall design process is good for the design process overall.
Design which is more accessible typically can benefit able-bodied
users as well by reducing fatigue, increasing their speed and
decreasing the number of errors made. As in the elevator example,
consideration of disability issues can also cause us to see design
issues more clearly, leading to new insights and better overall
design.
Creating more accessible designs can also increase the market for
many consumer products. With increasing awareness of the
accessibility issues, people are beginning to look for more
accessible designs. The Federal government, for example, has
recently passed legislation (Section 508 of Public Law 99-506 )
requiring that GSA develop accessibility guidelines that should
apply to all future electronic office equipment acquisitions
(purchase or lease). Similar measures are being examined by many
school systems and state governments.
Accessibility features should begin to provide a market edge even
in the home market. Although only one in five or six individuals
in the United States has a significant functional limitation, a
much higher percentage of households have individuals who have
functional limitations. Products purchased for use in a household
that has even one member with a disability may be more attractive
if their design is more accessible. More accessible design will
also increase the useful product life of many products purchased by
or for individuals who are aging.
Finally, as noted above, there are tremendous potential economic
benefits from making it easier for individuals with functional
limitations to live more independently and become or remain
employed.
What Are The Costs?
The most significant cost involved in considering functional
limitations in mainstream design is that of building the necessary
knowledge and skills in our human factors researchers, educators,
and practitioners. Before we can include the disability aspects in
our research and teaching, we must considerably expand our
knowledge base and experience in these areas. This is difficult
for most professionals, who already have difficulty keeping up with
the literature.
In order to include design for persons with functional limitations
in our college curricula, we will need to expand the content of our
already overcrowded courses and/or add courses to the already
difficult coursework requirements for our students. Since
incorporating individuals with limitations in our standard design
process does not eliminate the need for custom design of special
aids, we must also somehow address custom design for disability to
cover the needs that cannot be met through more accessible mass
market design.
CONCLUSION
Incorporating disability considerations in our research and
teaching will require substantial effort both as individuals and as
a field. Before we can effectively incorporate disability and
aging issues into our curriculum we will need to better define and
refine this area. The basic principles involved in accessible
design need to be explored and defined. More specific data
regarding the different areas of impairment as they relate to
design need to be gathered, condensed and made available to
researchers and designers. Some design guidelines exist (Lifchez &
Winslow, 1979; Sorenson, 1979; Newell, 1987; Newell & Cairns, 1987;
Calkins, 1988; Vanderheiden, 1988; Enders & Hall, 1990; Mueller,
1990) but much more work is needed in the delination and
documentation of the basic principles of accessible design.
It seems apparent, however, from the demographics and trends in our
population, that for an increasing number of the professionals and
educational programs in human factors, design for disability and
aging must merge with and become a continuum of the normal design
process. Aside from the significant benefits to society, these
efforts should also make our field more robust and lead it into new
directions and insights.
ACKNOWLEDGEMENTS
This work has been supported in part by Grant H133E80021 from the
National Institute on Disability and Rehabilitation Research.
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Newell, A.F., and Cairns, A.Y. (1987). Human interface
studies and the handicapped. Proceedings of the British
Computer Society Disabled Specialist Group Third
Conference.
Sarenson, R.J. (1979). Design for accessibility. New
York: McGraw Hill Book Company.
Technology and aging in America. (1985). Washington, DC:
US Congress, Office of Technology Assessment, OTA-BA-265.
Vanderheiden, G.C. (1988). Considerations in the design of
computers and operating systems to increase their
accessibility to persons with disabilities. Madison, WI:
Trace R&D Center Reprint Service, 1500 Highland Avenue,
Madison, WI 53705.
FIGURES
FIGURE 1. People's ability vary along a continuum for any given
dimension (vision, hearing, etc.). Their ability to use a
particular design would also vary along a continuum.
FIGURE 2. Although all but one person would be included in the
90th percentile data along any one dimensions (vision, hearing,
height, ambulation, and manual abilities), only 50% of this example
population would fall into the 95th percentile across all
dimensions simultaneously. A product which required 90th
percentile performance across these 5 dimensions would only be
usable by half this population.
FIGURE 3. Percent of U.S. population with selected impairments.
FIGURE 4. Prevalence of impairments (primary diagnosis) for school
aged children (3-21 yrs)
FIGURE 5. Prevalence of selected impairments within age groups.
FIGURE 6. Functional limitations as a function of age.
FIGURE 7. The graying of America.
FIGURE 8. Disability expenditures: Public and private sectors.
BIOGRAPHY
GREGG C. VANDERHEIDEN is the Director of the Trace R&D Center and
Assistant Professor in the Department of Industrial Engineering at
the University of Wisconsin-Madison. His research and teaching
are focused on the area of technology and human disability/aging.
Dr. Vanderheiden has a B.S. in electrical engineering, an M.S. in
biomedical engineering and a Ph.D. in Technology in Communication
Rehabilitation and Child Development from the University of
Wisconsin-Madison. The Trace Center is an interdisciplinary
research center in Rehabilitation Engineering which is concerned
with the areas of communication, control, and computer access and
use by persons with disabilities or reduced capacity.