ISO/TR 22411:2021

TECHNICAL ISO/TR
REPORT 22411
Second edition
2021-01
Ergonomics data for use in the
application of ISO/IEC Guide 71:2014
Données ergonomiques destinées à être utilisées dans le cadre de
l'application du Guide ISO/IEC 71:2014
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Supporting ISO/IEC Guide 71 with human data . 2
5 Data selection and format . 3
5.1 Data selection . 3
5.2 Data format of this document . 4
5.3 How to use the data . 5
6 Sensory characteristics and capabilities . 5
6.1 Overview of sensory characteristics and capabilities . 5
6.2 Vision . 6
6.2.1 Visual sensitivity to colour (spectral sensitivity of the eye: ageing effect). 6
6.2.2 Colour category (spans of fundamental colour, young people, older
people, and people with low vision) . 9
6.2.3 Colour category (international comparison) .22
6.2.4 Contrast sensitivity (young people, older people and people with low vision) .25
6.2.5 Contrast for legibility (ageing effect) .28
6.2.6 Visual acuity (effects of age, viewing distance and luminance) .32
6.2.7 Minimum font size for legibility (effects of age, viewing distance and
luminance) .35
6.2.8 Minimum font size for legibility (international comparison) .37
6.2.9 Minimum font size for legibility (low vision) . .41
6.2.10 Disability glare (ageing effect) .44
6.2.11 Useful field of view (ageing effect) .47
6.2.12 Lighting level and visual performance (ageing effect) .52
6.2.13 Visibility of an indicator lamp: Context and task specific data (effects of
ageing and low vision) .55
6.3 Hearing .58
6.3.1 Hearing-sensitivity decrease as a function of age .58
6.3.2 Tone perception in quiet conditions (ageing effect) .60
6.3.3 Sensitivity to low-frequency tones (ageing effect) .62
6.3.4 Equal-loudness-level contours (ageing effect) .64
6.3.5 Tone perception in noisy conditions (ageing effect) .67
6.3.6 Sound pressure level of spoken announcements in public space (ageing effect) .70
6.3.7 Audible conditions for speech communication in a noisy environment
(ageing effect) .72
6.4 Touch .75
6.4.1 Tactile pressure sense and spatial resolution (ageing effect) .75
6.4.2 Tactile spatial resolution (people with visual disabilities) .77
6.4.3 Tactile spatial resolution (body location and ageing effect) .78
6.4.4 Tactile temporal resolution (sensitivity to vibration, ageing effect) .81
6.4.5 Legibility of tactile symbols and characters (effects of ageing and
experience in the use of tactile symbols and characters for people with
visual disabilities) .83
6.4.6 Legibility of tactile symbols and characters (international comparison) .85
6.5 Thermal sense .88
6.5.1 Surface temperature (ageing effect) .88
6.5.2 Air temperature (ageing effect) .89
6.5.3 Thermal comfort (physical disabilities) .92
7 Physical characteristics and capabilities .99
7.1 Overview of physical characteristics and capabilities .99
7.2 Physical characteristics related to body size . .101
7.2.1 Basic body size (design range from small to large size) .101
7.2.2 Grip diameter (ageing effect) .104
7.3 Movement – fine hand use abilities .106
7.3.1 Hand steadiness (ageing effect) .106
7.3.2 Eye-hand coordination (dexterity, ageing effect) .107
7.4 Movement – functions of upper body structure .110
7.4.1 Reach range (effects of ageing and stature) .110
th
7.4.2 Reach range (graspability, female 5 percentile of body size) .115
7.4.3 Reach range in three dimensions of height, forward distance (depth), and
left-right width for older people and people with disabilities (rheumatism
and Parkinson’s disease) .117
7.4.4 Rotation: pronation and supination (ageing effect) .120
7.5 Movement – Functions of lower body structure .123
7.5.1 Step height (ageing effect) .123
7.5.2 Step height: Subjective evaluation of physical load (ageing effect,
international comparison) .126
7.5.3 Tread depth of stairs (ageing effect) .128
7.5.4 Walking speed (ageing effect) .130
7.5.5 Slope of ramps and wheelchair operation (physical disabilities) .133
7.6 Muscle strength and muscle endurance .134
7.6.1 Grip force of the hand (ageing effect) .134
7.6.2 Pressing force of the thumb .136
7.6.3 Compressive force of the index finger .138
7.6.4 Operating torque in four different conditions .140
7.6.5 Grip strength (ageing effect).144
7.6.6 Lifting strength (gender effect) .147
7.6.7 Lifting strength (effects of age and gender) .150
7.6.8 Pushing force with two hands (ageing effect) .152
7.6.9 Pulling force with one hand (ageing effect) .154
7.6.10 Pushing force with a finger (ageing effect) .156
7.6.11 Static torque with two hands (ageing effect) .158
7.6.12 Torque and force for opening packages (effects of ageing and disabilities) .160
7.6.13 Jar opening (perceived effort, older women) .164
7.6.14 Upper extremity muscle strength (ageing effect) .166
8 Cognitive characteristics and capabilities .170
8.1 Overview of cognitive characteristics and capabilities .170
8.2 Attention .171
8.2.1 Selective attention (selective listening, effect of age) .171
8.2.2 Dual task performance (task complexity, ageing effect).175
8.2.3 Memory under dual task conditions (effects of dual tasks and ageing) .177
8.3 Information processing .180
8.3.1 Processing speed and capacity .180
8.4 Memory .182
8.4.1 Effects of ageing and cognitive disabilities on memory .182
8.5 Language and literacy .184
8.5.1 Language use (ageing effects) .184
Annex A (informative) Additional textual descriptions of figures .186
Bibliography .234
iv © ISO 2021 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 159, Ergonomics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 122, Ergonomics, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO/TR 22411:2008), which has been
technically revised.
The main change compared to the previous edition is the replacement of ergonomics data on
human abilities and capabilities with new or more elaborated data for use in the application of
ISO/IEC Guide 71:2014.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
This document is intended to help standards developers by providing ergonomics data related to
human characteristics and capabilities to support ISO/IEC Guide 71:2014. This document is supposed to
be used mainly by standards developers, but also by those responsible for design. The underlying idea
is that products, services and environments encountered in all aspects of daily life and intended for the
consumer market and the workplace should be designed to be accessible for people with a widest range
of capabilities. This idea, called accessibility, has been spreading all over the world.
ISO/IEC Guide 71 was first published in 2001 to successfully address the importance of being aware
of the needs of older persons and persons with disabilities and to direct the attention of standards
developers to these needs when they draft or revise standards. In response to the publication of
ISO/IEC Guide 71, ISO/TR 22411:2008 was developed to fulfil the gap between the concept and practice
with offering ergonomic knowledge and data on human abilities.
After more than 10 years from the publication of ISO/IEC Guide 71 and ISO/TR 22411, together with
new knowledge and experience in implementing these documents, ISO/IEC Guide 71 was revised into a
more elaborated one and consequently the revision of ISO/TR 22411 was required.
This document provides updated ergonomics data as well as newly available data which are all publicly
available and can be used to support standards developers in applying ISO/IEC Guide 71:2014 in their
individual standards. These ergonomics data help standards developers to understand characteristics
and capabilities of diverse users to be served by requirements and recommendations in a standard.
The data provided in this document apply mainly to persons with disabilities and older persons.
The intention in using these data is to formulate requirements and recommendations in standards
that include the widest possible range of users. It can also be used by designers in order to increase
accessibility as part of accessible design or universal design.
While the data covers a wide area of human abilities related to accessibility, data for some part of the
area, for example cognitive abilities, is still missing. Furthermore, new data emerged or were updated
during the development of this document, which is not included in this document either. This document,
due to scientific reasons, does not necessarily adopt the ICF terminology but established terms in
ergonomics.
vi © ISO 2021 – All rights reserved

TECHNICAL REPORT ISO/TR 22411:2021(E)
Ergonomics data for use in the application of ISO/IEC
Guide 71:2014
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing
this document using a colour printer.
1 Scope
This document provides ergonomics data for standard developers to use in applying
ISO/IEC Guide 71:2014 to address accessibility in standards. These data can also be used by ergonomists
and designers to support the development of more accessible products, systems, services, environments,
and facilities.
The ergonomics data include quantitative data and knowledge about basic human characteristics and
capabilities as well as context-specific and task-specific data, all being based on ergonomics research.
The data focused on the effects of ageing and/or consequences of various types of human sensory,
physical, and cognitive disabilities. It does not contain general ergonomics data that have no direct
relation to ageing or disabilities.
The data presented in this document are not exhaustive due to no available data for some aspects of
human characteristics and capabilities with regard to ageing and disabilities.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
accessibility
extent to which products, systems, services, environments and facilities can be used by people from a
population with the widest range of user needs, characteristics and capabilities to achieve identified
goals in identified contexts of use
Note 1 to entry: Context of use includes direct use or use supported by assistive technologies.
[SOURCE: ISO 9241-112:2017, 3.15]
3.2
accessible design
design focused on diverse users to maximize the number of potential users who can readily use a
system in diverse contexts
Note 1 to entry: This aim can be achieved by (1) designing systems that are readily usable by most users without
any modification, (2) making systems adaptable to different users (by providing adaptable user interfaces) and
(3) having standardized interfaces to be compatible with assistive products and assistive technology.
Note 2 to entry: Terms such as universal design, accessible design, design for all, barrier-free design, inclusive
design and transgenerational design are often used interchangeably with the same meaning.
[SOURCE: ISO/IEC Guide 71:2014, 2.19]
3.3
impairment
problem in body function or structure related to a significant deviation or loss
Note 1 to entry: Impairments can be temporary or permanent; progressive, regressive or static; intermittent or
continuous.
[SOURCE: ICF 2001, WHO]
3.4
system
product, service, or built environment or any combination of them with which the user interacts
[SOURCE: ISO/IEC Guide 71:2014, 2.1]
3.5
universal design
design of products, environments, programmes and services to be usable by all people, to the greatest
extent possible, without the need for adaptation or specialized design
Note 1 to entry: Universal design shall not exclude assistive devices for particular groups or persons with
disabilities where this is needed.
Note 2 to entry: Terms such as universal design, accessible design, design for all, barrier-free design, inclusive
design and transgenerational design are often used interchangeably with the same meaning.
[SOURCE: ISO/IEC Guide 71:2014, 2.18]
3.6
user
individual who accesses or interacts with a system
[SOURCE: ISO 9241-11:2018, 3.1.5, modified — In the definition, "person" has been changed to
"individual", "accesses or" has been added, and "product or service" has been removed.]
4 Supporting ISO/IEC Guide 71 with human data
ISO/IEC Guide 71:2014 provides standards developers with guidance on addressing accessibility in
standards through two approaches, as shown in Figure 1:
1) the first approach defines accessibility goals for the product or system under development and the
user accessibility needs associated with fulfilling those goals (denoted by Clause 6 in Figure 1);
2) the second approach provides accessibility-related design considerations, based on an
understanding of human abilities and characteristics (denoted by Clause 7 in Figure 1).
2 © ISO 2021 – All rights reserved

Figure 1 — Two approaches to address accessibility in standards described in
ISO/IEC Guide 71:2014
The user accessibility needs (first approach) or design considerations (second approach) can serve
as the basis for accessibility requirements and recommendations in standards. Regardless of which
approach is used, the accessibility requirements and recommendations in the standards are derived
through the appropriate selection of strategies (denoted by Clause 8 in Figure 1) that can meet the
accessibility needs or address the design considerations.
Ergonomics data are relevant throughout both approaches and especially important in determining
which strategies are the most effective in a situation. In some cases, the data can provide a source
of nominal values or numerical specifications which can be included in the requirements and
recommendations of standards. In other cases (especially with respect to cognitive variables), the
available data are qualitative in nature and/or reflect small sample sizes, but can still be used to
evaluate the feasibility of applying particular strategies to meet accessibility needs or to address design
considerations.
In addition to the role that ergonomics data play in standards development, these data are directly
relevant to the product and system designers, who are attempting to fulfil accessibility requirements and
recommendations by developing and implementing technical solutions that make use of the existing data.
One of the challenges for standards developers and designers is that ergonomics data relevant to
specific populations is distributed across multiple standards and other guidance documents, as well as
in published research reports, papers and books from a variety of academic disciplines. The purpose
of this document is to bring the most valid and applicable data together in one document. This will
assist standards developers to address accessibility and consider the widest range of user needs when
formulating requirements and recommendations. Having a single source of information will also be of
value to designers.
5 Data selection and format
5.1 Data selection
The data in this document were selected from various sources existing in scientific books and journals,
standards, as well as databases of universities, research institutes or projects. They are all relevant for
demonstrating effects of ageing and disabilities and the committee regards valid and worth citing in
this document. Most of the data are well-supported in academia and related technical fields or based on
a sufficient number of samples to provide statistical meaningful results. Some of the data, especially in
cognitive field, have a limited number of samples but the committee regards qualitatively relevant for
application.
5.2 Data format of this document
Data in this document are presented in a common format for easy and correct understanding of the
data. It contains following items. If no information is available for some items, they are left blank.
— Title
This item describes the title of the data. The title has an additional information on the type of data
either for the effect of ageing or the effect of some specific disability.
— General
This item describes background and outline of data, implications in designing, as well as why
the data is important and included in this document. Some scientific information necessary to
understand the data is also included.
— Sampled population
This item describes samples from which the data have been obtained. Number of people who
participated in the experiments or measurements, their age and gender distribution, and any other
attributes of samples necessary for understanding the data are presented.
— Methods and conditions of data collection
This item describes methods and conditions of the measurement used for data collection. Technical
information necessary for understanding the figures and tables in the data section is provided
depending on the types of human characteristics and capabilities. Limitations associated with the
methods or conditions are also provided.
— Data
This item describes typical data given in figures and tables picked up from the data source(s) that
would be most suitable for understanding the human characteristics and capabilities expressed in
the title of the data. The data is also selected as the most useful one for design considerations.
— Limitations
This item describes constrains or cautions for use of the data. As the human data largely depends on
the methods and conditions of the measurement, it would be safe and useful to show the limitations
in applying the data to actual situations.
— Application examples
This item gives a general idea for applying the data and implication of the data for design with some
examples. This includes not only specific design examples but also how to use the data in general.
— References
This item provides a list of:
— Data sources: sources of information on the data presented in the data item, including relevant
literature (standards, academic journals, books, other reports) and website;
— Cross-references: relevant sections in this document for cross-referencing and better
understanding of the section;
— Other references: relevant literature and website, not directly related to the data but useful for
understanding them.
4 © ISO 2021 – All rights reserved

5.3 How to use the data
This document provides data on a large variety of human characteristics and capabilities that can be
applied to product design, as well as some aspects of the design of services and environments.
Clause 6 provides data items on sensory characteristics and capabilities covering modalities of vision,
hearing, touch, and the thermal sense. No data is provided on smell and taste as no relevant data source
was found, though ISO/IEC Guide 71 does address these senses in a general way.
Clause 7 provides data items on physical characteristics and capabilities, covering body size, fine motor
coordination of the hand, movement of upper body structures, movement of lower body structures, and
muscle power and muscle endurance. No data is provided on physical characteristics and capabilities
related to speech production.
Clause 8 provides data items on cognitive characteristics and capabilities related to attention,
information processing and memory. Although cognitive abilities are especially relevant to accessibility,
little data of quantitative nature exists because cognitive disabilities vary markedly in their effects
and can involve many unique combinations of attentional, information processing, memory, decision-
making and affective impairments for any given individual.
The data provided in this document can be used, directly or indirectly, when standard developers and
products designers consider accessibility in the context of developing standards or designing products,
services or environments. Depending on the nature of experimental data provided, it may or may not
be relevant to a specific design issue. Therefore, users of this document should consider whether the
data provided in this document can be applied in their specific situation, given how it was collected
(i.e. the population tested and the method used), as well as the limitations of the data, as described in
subclauses.
In addition, much of the data related to physical and sensory capabilities can be directly applied because
numerical values are provided in tables, charts, formulas and graphics. These data may be directly used
to set limit values in standards (e.g. weight-lifting limit), or specifications of certain design parameters
(e.g. the grip span for a tool). Alternatively, much of the data related to cognitive abilities simply is in
the form of task-specific trends, as a function of age and/or disability, and cannot be applied directly.
In these cases, designers and standards developers are limited to interpreting the implications of
the trends in light of their particular design or standards development situation. It is also extremely
important that users of the cognitive data maintain awareness of the significant variance in cognitive
capabilities and limitations, generally, and the limited sample sizes involved for some populations for
which data is provided.
6 Sensory characteristics and capabilities
6.1 Overview of sensory characteristics and capabilities
Every sensory characteristic and capability can be affected by ageing: abilities to detect, discriminate
or perceive sensory stimuli of vision, hearing, touch or thermal sense. How the change occurs varies
depending on the sensory function.
Various types of disabilities in sensory characteristics and capabilities are caused by medical disorders
or impairments in the structure or the function, which result in low vision, colour defect, hardness of
hearing, etc. In addition, disabilities can be caused by environmental factors such as illumination, noise,
temperature, etc.
Most of the sensory characteristics and capabilities do not vary depending on the gender or ethnicity.
However, in the case of hearing, for example, a large gender difference can be found in the sensitivity of
older ears although the reason for that is not known.
Table 1 shows a brief summary of sensory characteristics and capabilities with regard to ageing effects.
Details are described in 6.2 to 6.5. The sense of taste and olfaction is missing in this document because
of a lack of data useful for ergonomic design.
An online database can be used to investigate the ageing effects and effects of disabilities in sensory
characteristics and capabilities (see Reference [77]). Some of the data referenced in this document have
been taken from the database.
Overview of ageing effects on vision is also available in Reference [59].
Table 1 — List of major sensory functions and effects of aging
Sensory functions Particular effects of age
Vision
Spectral sensitivity Declines at short-wave region (blue light)
Colour discrimination Worsened
Colour identification/colour category Span of colour category reduced
Contrast sensitivity Declines at high spatial frequencies
Temporal sensitivity (flicker sensitivity) Declines at high temporal frequencies
Worsened at high spatial frequencies and at
Visual acuity
short viewing distance
Legibility (of symbols and letters) Worsened for complex symbols and letters
Field of view Narrowed
Dark/light adaptation Slightly affected
Lighting level Slightly affected
Glare Increased
Hearing
Hearing sensitivity Declines especially at high frequencies
Sensitivity to extremely high frequency (above 10 000 Hz) Declines or completely lost
Sensitivity to low frequency (below 100 Hz) Moderately affected
Becomes smaller especially at high frequencies;
Loudness in some cases, accompanies abnormal growth
called “recruitment”
Tone perception Worsened especially in noisy conditions
Speech perception Worsened especially in noisy conditions
Touch
Tactile pressure sense Sensitivity decreased
Spatial resolution Declines at high spatial frequencies
Sensitivity decreased especially for high tem-
Temporal sensitivity (for vibration)
poral frequencies
Legibility (for tactile symbols and characters) Worsened
Thermal sense
Sensitivity to surface temperature Decreased
Sensitivity to air temperature Decreased
Thermal sensation for comfort Reduced
6.2 Vision
6.2.1 Visual sensitivity to colour (spectral sensitivity of the eye: ageing effect)
6.2.1.1 General
The human eye responds to electro-magnetic radiation of the wavelength range from about 380 nm to
780 nm. The overall sensitivity to the radiation throughout the range is called spectral sensitivity or
spectral luminous efficiency. This spectral sensitivity changes with age so that it becomes less sensitive
6 © ISO 2021 – All rights reserved

to light in the short-wavelength region approximately from 400 nm to 500 nm (coloured purplish and
bluish). Therefore, a bluish as well as a purplish light looks darker to older persons than it does to young
persons. Taking account of this ageing effect can increase visibility of signs and displays for older people.
NOTE This ageing effect disappears if an older person has had his/her lens replaced with an artificial eye
lens surgically implanted, as the effect is caused mainly by yellowing of the lens.
6.2.1.2 Sampled population
Data were collected from 91 participants ranged in age from 12 years to 78 years. The distribution
of ages of the participants were 6 people in 10–19 years, 11 people in 20–29 years, 10 people in 30–
39 years, 10 people 40–49 years, 10 people in 50–59 years, 28 people in 60–69 years, and 16 people in
70–79 years. The numbers of male and female participants were nearly equal.
6.2.1.3 Methods and conditions of data collection
The data were measured by the conventional method for visual sensitivity called flicker photometry. In
this measurement, a test light and a reference light, both of which were subtended at a visual angle of
about 2° at the same location on the retina, were temporally alternated with a fixed frequency of 12 Hz.
A non-flicker or a minimum flicker point was determined by adjusting the intensity of the test light,
in most cases, while that of the reference light was fixed. The minimum flicker point was regarded as
the equal luminance of the test and reference light to the eye. The test light was chosen from a range of
420 nm to 700 nm in 10 nm steps. The amount of each test light needed to reach to the equal luminance
level gives the reciprocal of spectral sensitivity data.
6.2.1.4 Data
Figure 2 shows the spectral sensitivity data measured for 91 people by flicker photometry with a
foveally fixed 2-degree target field at a photopic level. The data are classified into seven age groups in
10-year steps and the geometric average over all the participants in a decade is expressed as a solid line.
The data shows clear reductions of sensitivity in the short-wave region (blue light) with ageing, while
there is almost no change at middle-wave (green light) and long-wave (red light) regions. This means
that blue light, which contains a short-wave component, looks darker to older people than it does to
young people. This age-related change occurs gradually and smoothly from the youngest age, and the
maximum difference reaches about one tenth (or 10 times) when the data of 10–19 years old and 70–
79 years old are compared.
Key
X wavelength (nm)
Y relative sensitivity
A average of people in their 10s
B average of people in their 70s
Figure 2 — Spectral sensitivity curves of the human eye for seven age groups from 11 to
78 years
6.2.1.5 Limitations
The data presented here are only for people with normal colour vision, and do not apply to people with
defective colour vision nor with low vision.
6.2.1.6 Application examples
The main application of human spectral sensitivity is in the measurement of light in terms of visual
sensation of lights or objects (photometry or visually meaningful measurement of light), i.e. brighter or
darker. The sensitivity data for young people without any visual impairment has been standardized by
the International Commission on Illumination (CIE) and has been traditionally used in the measurement
of light which is visually meaningful. The age-related change in the sensitivity shown in Figure 2 has
not been officially established yet in the field of photometry, but can be practically used in evaluating
lights for people in any range of age, in particular for older people, in the same manner as it is used in
photometry.
Evaluating the visibility of blue lights for older people in traffic signs, emergency signs and other
critical displays, in particular, can increase the accessibility of those signs. Designers should increase
light intensity when possible if they use blue lights (blue LEDs, for example) against dark backgrounds
in signage used by older people.
Figure 3 shows an example of visual sign composed of blue letters on a dark yellow (brown) background.
Using spectral sensitivity curves of people in their 20s and 70s respectively, the contrast ratio of this
sign is much lower for older people (1,13 for those in their 70s) than for young people (2,07 for those in
their 20s). Nearly twice as much luminance of blue light is needed for older people to achieve the same
contrast as young people. This colour combination example is a typical one regarded as hard to see for
older people but not to young people. For other colour combinations, this contrast difference may be
smaller, but care should be taken for any colour combination when blue light is used in a sign.
8 © ISO 2021 – All rights reserved

Key
X wavelength (nm)
Y spectral radiance (watt/m )
A blue letter
B dark yellow background
C contrast for an observer in his/her 20s [2,07 (= 0,003 1 / 0,001 5)]
D contrast for an observer in his/her 70s [1,13 (= 0,001 8 / 0,001 6)]
E sample sign
a luminance of a blue letter to people in their 20s (0,003 1 relative unit)
b luminance of a dark yellow background to people in their 20s (0,001 5 relative unit)
c luminance of a blue letter to people in their 70s (0,001 8 rel. unit)
d luminance of a dark yellow background to people in their 70s (0,001 6 relative unit)
Figure 3 — An application of spectral sensitivity for calculating contrast of a coloured sign
More information on the implication and use of the spectral sensitivity data are presented in ISO 24502.
6.2.1.7
...