Jan Gulliksen, Susan Harker and John Steger.
CID, CENTRE FOR USER ORIENTED IT DESIGN
CID-121 ISSN 1403-0721 Department of Numerical Analysis and Computer Sience KTH
The ISO Approach to the Development of Ergonomics
Standards for Accessibility
Författare: Jan Gulliksen, Susan Harker and John Steger
The ISO Approach to the Development of Ergonomics Standards for Accessibility.
Report number: CID-121
ISSN number: ISSN 1403-0721 (print) 1403-073X (Web/PDF)
Publication date: 2001
E-mail of author: firstname.lastname@example.org
URL of author: http://cid.nada.kth.se
Reports can be ordered from:
CID, Centre for User Oriented IT Design
NADA, Deptartment of Numerical Analysis and Computer Science
KTH (Royal Institute of Technology)
SE-100 44 Stockhom, Sweden
Telephone: +46 (0) 8 790 91 00
Fax: + 46 (0) 8 790 90 99
ISO 16071 Ergonomics of human-
system interaction – guidance on
Department of HCI, Information Technology, Uppsala University, Uppsala,
Center for user-oriented IT-design (CID), Royal Institute of Technology,
Loughborough Institute of Technology, United Kingdom
IBM, United States of America
This chapter reports on the work currently performed by the International
Organization for Standardization (ISO) on accessibility of human-computer
interfaces. ISO Technical Specification 16071 “Ergonomics of human-system
interaction – guidance on software accessibility” will be published by the end of
With the increasing interest in designing usable systems and the increasing the
level of accessibility for people with specific potential requirements, the
International Organisation for Standardisation has been conducting work resulting
in a ISO Technical Specification 16071 Ergonomics of human-system interaction –
guidance on software accessibility.
Here I would like an introduction that stresses the importance of addressing
the growing population of users who need extra support to be able to handle
computer support. How big are these groups? I know that we can find information
in the Nordic guidelines.
What are the incitements to support this type of work? E.g. referencing ADA
(American Disabilities Act)
INTERNATIONAL ORGANISATION FOR STANDARDIZATION (ISO)
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The International Organization for Standardization (ISO) is a worldwide federation
of national standards bodies from some 130 countries, one from each country. ISO
is a non-governmental organisation established in 1947. The head office is in
Geneva. The mission of ISO is to promote the development of standardisation and
related activities in the world with a view to facilitating the international exchange
of goods and services, and to developing co-operation in the spheres of
intellectual, scientific, technological and economic activity. ISO's work results in
international agreements, which are published as International Standards.
ISO standards are developed according to the following principles:
• Consensus – The views of all interests are taken into account: manufacturers,
vendors and users, consumer groups, testing laboratories, governments,
engineering professions and research organisations.
• Industry-wide – Global solutions to satisfy industries and customers
• Voluntary – International standardisation is market-driven and therefore based
on voluntary involvement of all interests in the marketplace.
The international standard described in this document is provided by ISO TC
159/SC 4/WG 5 “Software ergonomics and human computer dialogues”. WG 5 is
the group behind the software parts of ISO 9241 “Ergonomic requirements for
office work with visual display terminals (VDTs)”, that is parts 10 through 17.
WG 5 is also currently preparing ISO 14915 “Multimedia User Interfaces”.
Guidance on Accessibility of Human Computer Interfaces – ISO 16071 is not
an international standard, but a Technical Specification (TS). A TS is a new format
for ISO documents presented at first in 1998. It is a normative document
representing the technical consensus within an ISO committee. The purpose is that
a technical specification within a period of six years should be converted into an
international standard or be withdrawn.
THE INTRODUCTION TO ISO TS 16071
The purpose of ISO Technical Specification 16071 is to provide guidance to
developers on designing human-computer interfaces which can be used with as
high level of accessibility as possible. Designing human computer interactions to
increase accessibility promotes increased effectiveness, efficiency, and satisfaction
for people who have a wide variety of capabilities and preferences. Accessibility is
therefore strongly related to the concept of usability (ISO 9241 Part 11 – Guidance
The most important methodological approaches to increase the accessibility
of a given human-computer interface are:
• Task-oriented design of user interfaces.
• The use of human centred design principles (ISO 13407 - Human centred
design process for interactive systems).
• Individualised user instruction and training.
The focus of ISO TS 16071 is development of human computer interactions to
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systems and products that are intended for use by the widest range of people with
special needs. An important part of a human centred design process for accessible
systems is to develop human-computer interfaces to meet accessibility goals that
can be quantitatively evaluated for a specific user or user category in a specified
context of use.
The ISO Technical Specification 16071 is based mainly on the prevalent
knowledge of individuals with sensory and/or motor impairments in an office
work context. However, accessibility is an attribute that affects a large variety of
capabilities and preferences of human beings. These different capabilities may be
the result of age, disease, and/or disabilities. Therefore, accessibility addresses a
widely defined group of users including:
• people with physical, sensory and cognitive impairments by birth or acquired
• elderly people who can benefit from new IT products and services but
experience reduced physical, sensory and cognitive abilities
• people with temporary disabilities such as a person with a broken arm or
someone who forgot her glasses
• people who are experiencing difficulties in certain situations, such as a person
who works in a noisy environment or has both hands occupied by other work.
Having a disability should be regarded as a natural element of the life cycle.
Everyone can expect, during some period of life, to be affected by circumstances
that make the access to ad use of IT systems products and services difficult.
ISO TS 16071 recognises that some users will always need assistive devices
to use a system. Therefore, it includes the capability of a system to connect and
interact successfully with assistive technologies in the concept of accessibility.
ISO TS 16071 provide guidance for system design, appearance and
behaviour. The guidance will allow software to be used by as broad an audience as
possible. In addition, guidance will be provided on designing software to
integrate as effectively as possible with common assistive technologies (e.g.,
speech synthesisers, Braille input and output devices) when they are available.
Incorporating accessibility features early in the design process is relatively
inexpensive compared to the cost of modifying products to become accessible.
ISO TS 16071 addresses the increasing need to consider the social and
legislative demands to ensure accessibility by removing barriers that prevent them
from participating in life activities including the use of environment, services,
products, and information. Designing software user interfaces for accessibility
increases the number of people who can use computer systems by taking into
account the varying physical and sensory capabilities of user populations.
Designing for accessibility benefits disabled users by making software easier for
them to use or making the difference in whether they are able to use the software at
Many accessibility features also benefit users who are not handicapped by
enhancing usability and providing additional customisation possibilities. They
may also help to overcome temporary deficits (e.g., a broken arm or hand). ISO
TS 16071 benefits designers and suppliers by expanding the number of potential
users (and thus sales for their product) and often by making the product compliant
with legal requirements for accessibility. It benefits companies buying software by
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expanding the number of employees who may use the software.
Accessibility may be provided by a combination of both hardware and
software. Assistive technologies typically provide specialised input and output
capabilities not provided by the system. Software examples include on-screen
keyboards that replace physical keyboards, screen magnification software that
allows users to view their screen at various levels of magnification, and screen
reading software that allows blind users to navigate through applications,
determine the state of controls, and read text via text to speech conversion.
Hardware examples include head-mounted pointers that replace mice and Braille
output devices that replace a video display. There are many other examples not
listed here. When users provide add-on assistive software and/or hardware,
usability is enhanced to the extent that systems and applications integrate with
those technologies. For this reason, operating systems may have to provide
“hooks” or other features to allow software to operate effectively with add-on
assistive software and hardware as recommended in these guidelines. If systems do
not provide support for assistive technologies, the probability increases that users
will encounter problems with compatibility, performance, and usability. At the
same time, if software applications do not use system provided mechanisms (such
as customisation for colour, font, and audio, or system routines for keyboard
navigation and text input), then users can find their access blocked.
SCOPE OF THE ISO 16071
ISO Technical Specification 16071 provides guidance on design of accessible
(work, home, education) software. It covers issues associated with designing
accessible software for the widest range of visual, hearing, motor and cognitive
abilities, including people who are elderly and temporarily disabled. This
Technical Specification addresses software considerations for accessibility that
complements general usability design covered by ISO 9241 and ISO 13407.
The Technical Specification covers accessibility of computer operating
systems and applications. While it does not address all accessibility issues of
platforms and application domains such as web pages, multimedia, Personal
Digital Assistants (PDA), and kiosks, many of the recommendations are applicable
in these areas. It does not apply to software used primarily for entertainment
purposes (i.e., games). It does not provide recommendations for the design of
The Technical Specification is aimed at reducing the need for add-on assistive
hardware and software technologies while promoting increased usability of systems
in combination with assistive technologies, when they are required. It does not
cover the behaviour or requirements for assistive technologies themselves
(including assistive software).
DEFINING ACCESSIBILITY IN RELATION TO USABILITY
Our experience from the development and use of ISO 9241 part 11 is the benefits
of having a clear and succinct definition of the concept. ISO 9241:11 defines
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The extent to which a product can be used by specified users, to achieve specified
goals, with effectiveness, efficiency and satisfaction, in a specified context of use.
The advantage of such a definition is both that it defines usability to be a
quantitatively measurable concept. It also emphasises the non-functional demands
of usability that is so important for the final interpretation of the concept.
On the other hand we would want to define accessibility in relation to
usability as a measurable entity. Therefore ISO TS 16071 define accessibility as:
The usability of a product, service, environment or facility by people with the
widest range of capabilities.
This definition implicitly indicates that it is measurable through its relation to
usability. However, it is extended to cover more than just products (as in the
definition of usability), covering service, environment or facility. This definition
can be compared to the less precise definition from HFES 200 Software User
Interfaces – Accessibility:
The set of properties that allows a product, service or facility to be used by
people with a wide range of capabilities, either directly or in conjunction with
assistive technologies. Although “accessibility” typically addresses users who
have a disability, the concept is not limited to disability issues.
This definition suggests accessibility as of a binary nature, i.e. either a product is
accessible or not. This does not correspond with essence of the specific guidelines
in the document, why we suggest sharpening the definition to be quantitatively
measurable. As a comparison, the World Wide Web Consortium (W
accessibility in the following way:
Content is accessible when it may be used by someone with a disability.
products. To be able to compare the accessibility one must only vary one of these
terms at a time, e.g.:
RATIONALE AND BENEFITS OF ISO 16071
Accessibility is an important consideration in the design of products, systems,
environments and facilities because if effects the usability of people with the
widest possible range of capabilities.
Accessibility can be improved by incorporating features and attributes known
to benefit the users with specific special requirements. In order to determine the
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achieved level of accessibility, it is necessary to measure the performance and
satisfaction of users working with a product or interacting with an environment.
Measurements of accessibility is particularly important in view of the complexity
of the interactions with the user, the goals, the task characteristics and the other
elements of the context of use. A product, system, environment or facility can
have significantly different levels of accessibility when used in different contexts.
Planning for accessibility as an integral part of the design and development
process involves the systematic identification of requirements for accessibility
including accessibility measurements and verification criteria within the context of
use. These provide design targets that can be the basis for verification of the
The approach adopted in ISO Technical Specification 16071 has benefits,
• The framework can be used to identify the aspects of accessibility and the
components of the context of use to be taken into account when specifying,
designing or evaluating the accessibility of a product.
• The performance (effectiveness and efficiency) and satisfaction of the users can
be used to measure the extent to which a product, system, environment or
facility is accessible in a specific context.
• Measures of the performance and satisfaction of the users can provide a basis
for the comparison of the relative accessibility of products with different
technical characteristics, which are used in the same context.
• The accessibility planned for a product can be defined, documented and
verified (e.g., as part of a quality plan).
Who will be using such an ISO document? Today, many organisations have user
centred design groups within the organisations to take the responsibility for
ISO Technical Specification 16071 serves the following types of users:
• the user interface designer, who will apply the guidance during the
• the developer, who will apply the guidance during design and
implementation of system functionality.
• the buyer, who will reference the Technical Specification during product
• evaluators, who are responsible for insuring products meet the
recommendations of the Technical Specification.
• designers of user interface development tools and style guides to be used
by interface designers.
The ultimate beneficiary of this Technical Specification will be the end-user of the
software. Although it is unlikely that the end-users will read the Technical
Specification, its application by designers, developers, buyers and evaluators
should provide user interfaces that are more accessible. The guidelines concern the
development of software for user interfaces, however, those involved in designing
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the hardware aspects of user interfaces may also find them useful.
Here is one of the major problems that I think we have observed and that I would
want to discuss. How does the reader find the ISO-standard that is applicable to
them in a specific situation? One-stop-shopping could be achieved if all the
standards within ergonomics could be collected under one ISO-number.
Alternatively one could create a technical report with the purpose of explaining the
different standards and their interrelationship and possible use.
I could also fancy discussing the use of checklists to communicate knowledge.
The importance of making the presentation of the material attractive – today many
people regard the standards as so boring that one could die...
WHAT TYPES OF CAPABILITIES DO WE WANT TO ADDRESS?
The user characteristics of people with any given disability vary significantly just
as any other heterogeneous population. The descriptions contained here provide
only an outline of the issues typically encountered by individuals with various
disabilities, and do not constitute a comprehensive list. People may concurrently
experience more than one of the disabilities outlined below. The needs of people
who have such combinations of disabilities are covered in several cases by the
overlap across guidelines.
The following capabilities are specifically addressed in this standard
• users who are blind
• users who have low-vision
• users who are deaf
• users who have hearing impairments
• users who have physical impairments
• users who have cognitive impairments
• users who are elderly
• users who have temporary disabilities
• users who have multiple disabilities
• users who have environmental disabilities
Issues commonly encountered by users who are blind
The primary issue for users who are blind is how to obtain information provided
by visual presentation, how to navigate among objects on screens, how to identify
those objects, and how to control focus, navigation, and other functions via the
Many people who are blind from birth learn Braille, and many who become
blind later in life often rely on additional auditory methods to obtain information.
Many users who are blind often have some vision and primarily interact with
computers through “screen readers” -- assistive software that can provide spoken or
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Braille information for windows, controls, menus, images, text and other
information typically displayed visually on a screen.
Considerations for these users follow from the characteristics of interactions
mediated by screen readers. To the extent that interactions depend on
understanding a spatial metaphor for navigation or seeing a graphically represented
objects, users who are blind are more likely to encounter difficulties, and normally
keyboard navigation is an essential function.
In addition, because many users who are blind are reading screens by means
of synthesised speech output, they may find it difficult or impossible to attend to
auditory outputs that occur while they are reading.
Issues commonly encountered by users who have low-vision
The issues commonly faced by users who have low-vision include loss of visual
acuity, colour perception deficits, impaired contrast sensitivity, and loss of depth
People who have low-vision use varying means of increasing the size,
contrast, and overall visibility of visual displays depending upon their visual
needs. Common assistive technologies include use of oversized monitors, large
fonts, high contrast, and hardware or software magnification to enlarge portions of
When interacting with computers, these users may not detect size coding,
have difficulty with font discrimination, and encounter difficulties locating or
tracking interface objects such as pointers, cursors, drop targets, hot spots, and
direct manipulation handles.
Additionally, both blind and users who have low vision experience
difficulties when required to read very small displays, such as those on printers,
copiers, ticket machines and ATMs.
Issues commonly encountered by users who are deaf or hard of hearing
Users who are deaf or hard of hearing who retain some functional hearing include
the inability to discriminate frequency changes, decreased frequency range and
dropout, difficulties localising sounds, and difficulty picking up sounds against
Users who are deaf or hard of hearing may or may not use electronic hearing
aids, depending on the nature and extent of the hearing impairment. If it is
available in the operating system, they may use the “ShowSounds” feature that
notifies software to present audio information in visual form.
When interacting with computers, these users may have trouble hearing
sounds of certain frequencies, or of low volume. Sound customisation is key to
providing them with access.
Issues commonly encountered by users who are deaf
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In addition to a general inability to detect auditory information, the issues
commonly faced by users who are deaf may include the inability to produce speech
recognisable by voice input systems, and experience with a national language only
as a second language (sign language often being the primary language for people
who are born deaf or who become deaf at an early age).
If it is available, users who are deaf will typically use the “ShowSounds”
feature that notifies software to present audio information in visual form.
When interacting with computers, these users will encounter problems if
important information is presented only in audio form. Many of these issues apply
to any user in contexts where sound is masked by background noise (e.g., machine
shop floor) or where sound is turned off or cannot be used (e.g., a library).
Issues commonly encountered by users who have physical impairments
The issues commonly faced by users who have physical impairments often follow
from physical limitations including poor co-ordination, weakness, difficulty
reaching, and inability to move a limb.
Users with physical impairments may or may not use assistive technologies
and the variety of hardware and software they employ is too large to describe in
detail in this space. A few examples, however, include eye-tracking devices, on-
screen keyboards, speech recognition, and alternative pointing devices.
Some users may have difficulty directly manipulating objects, using modifier
keys, using pointing devices, and performing actions that require precise
movement or timing. Other users may have tremors that cause difficulty in
moving to a target. The extreme variation in needs and capabilities among this
user population means that customisation of input parameters and timing is
extremely important for effective access.
Issues commonly encountered by users who have cognitive impairments
The issues commonly encountered by users who have cognitive disabilities
involve difficulties receiving information, processing it, and communicating what
they know. People with these impairments may have trouble learning new things,
making generalisations and associations, and expressing them selves through
spoken or written language. Attention deficit hyperactivity disorders make it
difficult for a person to sit calmly and give full attention to a task.
The issues commonly faced by users who have dyslexia are difficulties
reading text that is presented in written form and difficulties in producing written
Reading difficulties is best supported by having the text that is highlighted
and read out loud or by providing “easy-reading” versions of the texts. Users
without reading difficulties also benefit from easy-reading versions of written text.
Providing support of synthetic speech for what is to be written best supports
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Issues commonly encountered by users who are elderly
Elderly users are progressively limited in their ability to use and access human-
computer interfaces due to the multiplicative effects of combinations of visual,
hearing, cognitive, and motor impairments that to varying degrees might come
with increasing age.
Sometimes the awareness of diminishing capabilities is a concern for elderly
users. Therefore, built-in accessibility of products contributes to removing the
stigma of special aids or modifications. Elderly persons do not want to have their
age regarded as a disability.
Issues commonly encountered by users who have temporary disabilities
Temporary disabilities are often of a physical nature (e.g. broken arm). These users
seldom adopt efficient skills in learning to cope with their disability. It is therefore
important to make the accessibility features for these disabilities easy to find and
learn to master.
Temporary disabilities might also be caused by repetitive strain caused by
poor ergonomics and intensive use of the computer system. It is then important
that this injury can be relieved through support that can be provided to the user via
For example, improving the design of the laptop computer so that it can be
opened with one hand also increases the usability for all users.
Issues commonly encountered by users who have multiple disabilities
There are not just a few categories of disabilities, rather the range of different
accessibility needs varies just as the combinations of certain degrees of disabilities
are a fact. For example, an individual with a cognitive impairment might also have
Several of the guidelines for addressing a specific disability might be
contradictory. For example, auditory output of written text is not a support for the
deaf blind. It is therefore important that the support for these forms of multiple
disabilities is individualised for the specific user and task.
Issues commonly encountered by users who have environmental disabilities
Environmental disabilities occur when specific features of the work environment
cause difficulties in perceiving signals from the computer. Such situations include
difficulties hearing signals from the computer, working in a noisy environment.
These situations must be regarded as disabling the user to fulfil the task with the
aid of the computer. Although this may not be a software requirement, the
immediate solution should be to improve the environment, and, in situations
where this can not be made, such as airports, provide redundant presentations of
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C has provided one of the most commonly used documents on
accessibility. The ISO working group had quite a discussion on whether the
material could be regarded as stable and how a standard could reference guidelines
that merely are provided on-line. The group went through all of the guidelines
provided in [W
C, 1999] and grouped them into the following categories;
• guidelines that are already covered by ISO 9241
• guidelines that are not of a general nature
• guidelines that should be included in the document.
The following decisions were made...
SUMMARY AND POSSIBLE FUTURE DEVELOPMENT EFFORTS
ISO TS 16071 Ergonomics of human-system interaction – guidance on software
accessibility will be published by the end of 2000. The intention of the group is to
move the document further and pursue the work to be an international standard.
The authors wish to acknowledge the entire subgroup on accessibility from ISO
Technical committee 159/Sub committee 4/Working Group 5. The input provided
by Human Factors and Ergonomics Society in terms of their outline of the
accessibility part of ANSI 200 is a significant contribution to the making of the
International Organization for Standardization (1998) ISO 9241 Software
ergonomics with visual display terminals (VDTs), Part 11 Guidance on Usability.
International standard. (Switzerland: International Organization for Standardization)
International Organization for Standardization (1999) ISO 13407 Human centred
design process for interactive systems. International standard. (Switzerland:
International Organization for Standardization)
International Organization for Standardization (2000) ISO 16071 Ergonomics of
human-system interaction – guidance on software accessibility. Technical
Specification. (Switzerland: International Organization for Standardization)
Thorén, C. (ed.) (1998). Nordic Guidelines for Computer Accessibility. 2
(Vällingby: Noordic Cooperation on Disability).
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World Wide Web Consortium (W
C), (1999) WAI - Web content accessibility
guidelines 1.0, May 5, 1999.