Ergonomics of the thermal environment - Evaluation of the thermal environment in vehicles - Part 3: Evaluation of thermal comfort using human subjects (ISO 14505-3:2006)

This part of ISO 14505 gives guidelines and specifies a standard test method for the assessment, using human subjects, of thermal comfort in vehicles. It is not restricted to any particular vehicle but provides the general principles that allow assessment and evaluation. The method can be used to determine a measure of the performance of a vehicle for conditions of interest, in terms of whether it provides thermal comfort to people or not. This can be used in vehicle development and evaluation. This part of ISO 14505 is applicable to all types of vehicles, including cars, buses, trucks, off-road vehicles, trains, aircraft, ships, submarines, and to the cabins of cranes and similar spaces. It applies where people are enclosed in a vehicle and when they are exposed to outside conditions. For those exposed to outside conditions, such as riders of bicycles or motorcycles, drivers of open sports cars and operators of fork lift trucks without cabins, vehicle speed and weather conditions can dominate responses. The principles of assessment, however, will still apply. This part of ISO 14505 applies to both passengers and operators of vehicles where its application does not interfere with the safe operation of the vehicle. It presents the principles of the assessment and evaluation of thermal comfort, including the use of test methods and trials. It also presents subjective methods that can be used in assessment. This part of ISO 14505 is a basic ergonomics standard which can contribute to the development of standards concerned with specific vehicles and products.

Ergonomie der thermischen Umgebung - Bewertung der thermischen Umgebungen in Fahrzeugen - Teil 3: Bewertung der thermischen Behaglichkeit durch Versuchspersonen (ISO 14505-3:2006)

Dieser Teil von ISO 14505 enthält Leitlinien und legt ein genormtes Prüfverfahren für die Beurteilung der thermischen Behaglichkeit in Fahrzeugen durch Versuchspersonen fest. Er ist nicht auf bestimmte Fahrzeuge beschränkt, sondern liefert die allgemeinen Grundsätze für Beurteilung und Bewertung. Das Verfahren kann zur Bestimmung eines Maßes für die Leistung eines Fahrzeuges unter den interessierenden Bedingungen verwendet werden, um festzustellen, ob eine thermische Behaglichkeit für die Personen möglich ist. Dies kann sowohl bei der Entwicklung als auch bei der Bewertung von Fahrzeugen verwendet werden.
Dieser Teil von ISO 14505 ist für alle Arten von Fahrzeuge einschließlich Autos, Bussen, Lastkraftwagen, geländegängigen Fahrzeugen, Zügen, Flugzeugen, Schiffen, U Booten, Führerkabinen von Kranen und ähnlichen Räumen anwendbar. Er gilt für Situationen, in denen sich Personen in einem geschlossenen Fahrzeug befinden, aber auch für solche, in denen sie den Bedingungen im Freien ausgesetzt sind. Bei den Personen, die den Bedingungen im Freien ausgesetzt sind, beispielsweise bei Benutzern von Fahrrädern oder Motorrädern, Fahrern von Sportwagen und Gabelstaplern ohne Führerkabinen, werden möglicherweise die Reaktionen verstärkt durch die Fahrzeuggeschwindigkeit und die Wetterbedingungen beeinflusst sein. Die Grundsätze der Beurteilung gelten jedoch auch hier weiterhin.
Dieser Teil von ISO 14505 gilt sowohl für Fahrgäste als auch Fahrer/Bediener von Fahrzeugen, sofern durch die Anwendung der Norm die sichere Bedienung des Fahrzeuges nicht beeinträchtigt wird.
Er enthält die Grundsätze zur Beurteilung und Bewertung der thermischen Behaglichkeit, ein¬schließlich der Anwendung von Prüfverfahren und Versuchen. Er enthält auch subjektive Verfahren, die bei der Beurteilung angewendet werden können.

Ergonomie des ambiances thermiques - Évaluation des ambiances thermiques dans les véhicules - Partie 3: Évaluation du confort thermique en ayant recours a des sujets humains (ISO 14505-3:2006)

L'ISO 14505-3:2006 donne des lignes directrices et spécifie une méthode d'essai pour l'évaluation du confort thermique offert par les véhicules, en faisant appel à des sujets humains. Elle ne se limite pas à un véhicule particulier mais pose des principes généraux permettant l'évaluation et l'appréciation. Cette méthode peut servir à mesurer les performances d'un véhicule dans des conditions déterminées et peut permettre de vérifier si celui-ci offre ou non un confort thermique à ses utilisateurs. Elle peut être utilisée pour le développement et l'évaluation des véhicules.
L'ISO 14505-3:2006 est applicable à l'ensemble des véhicules, y compris les voitures particulières, les autobus, les camions, les véhicules tout terrain, les trains, les aéronefs, les navires, les sous-marins, les cabines de grue et les espaces assimilés. Elle est applicable aux personnes prenant place dans un véhicule ainsi qu'à celles exposées aux conditions extérieures. Pour celles exposées aux conditions extérieures, par exemple les cyclistes, les motocyclistes, les conducteurs et passagers de voitures de sport et les opérateurs de chariots élévateurs à fourche sans cabine, la vitesse du véhicule et les conditions météorologiques peuvent constituer des facteurs dominants qui conditionnent les réponses. Cependant, les principes d'évaluation demeurent applicables.
L'ISO 14505-3:2006 est applicable aux passagers ainsi qu'aux conducteurs ou opérateurs des véhicules, dans la mesure où son application n'entrave pas la bonne marche et la sécurité du véhicule.

Ergonomija toplotnega okolja – Vrednotenje toplotnega okolja v vozilih – 3. del: Vrednotenje toplotnega ugodja s pomočjo preskusnih oseb (ISO 14505-3:2006)

General Information

Status
Published
Publication Date
30-Sep-2006
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Oct-2006
Due Date
01-Oct-2006
Completion Date
01-Oct-2006

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SLOVENSKI STANDARD
SIST EN ISO 14505-3:2006
01-oktober-2006
(UJRQRPLMDWRSORWQHJDRNROMD±9UHGQRWHQMHWRSORWQHJDRNROMDYYR]LOLK±GHO
9UHGQRWHQMHWRSORWQHJDXJRGMDVSRPRþMRSUHVNXVQLKRVHE ,62
Ergonomics of the thermal environment - Evaluation of the thermal environment in

vehicles - Part 3: Evaluation of thermal comfort using human subjects (ISO 14505-

3:2006)
Ergonomie der thermischen Umgebung - Bewertung der thermischen Umgebungen in

Fahrzeugen - Teil 3: Bewertung der thermischen Behaglichkeit durch Versuchspersonen

(ISO 14505-3:2006)

Ergonomie des ambiances thermiques - Évaluation des ambiances thermiques dans les

véhicules - Partie 3: Évaluation du confort thermique en ayant recours a des sujets

humains (ISO 14505-3:2006)
Ta slovenski standard je istoveten z: EN ISO 14505-3:2006
ICS:
13.180 Ergonomija Ergonomics
43.020 Cestna vozila na splošno Road vehicles in general
SIST EN ISO 14505-3:2006 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 14505-3:2006
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SIST EN ISO 14505-3:2006
EUROPEAN STANDARD
EN ISO 14505-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2006
ICS 13.180; 43.020
English Version
Ergonomics of the thermal environment - Evaluation of the
thermal environment in vehicles - Part 3: Evaluation of thermal
comfort using human subjects (ISO 14505-3:2006)

Ergonomie des ambiances thermiques - Évaluation des Ergonomie der thermischen Umgebung - Bewertung der

ambiances thermiques dans les véhicules - Partie 3: thermischen Umgebungen in Fahrzeugen - Teil 3:

Évaluation du confort thermique en ayant recours à des Bewertung der thermischen Behaglichkeit durch

sujets humains (ISO 14505-3:2006) Versuchspersonen (ISO 14505-3:2006)
This European Standard was approved by CEN on 12 May 2006.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official

versions.

CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,

Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,

Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14505-3:2006: E

worldwide for CEN national Members.
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SIST EN ISO 14505-3:2006
EN ISO 14505-3:2006 (E)
Foreword

This document (EN ISO 14505-3:2006) has been prepared by Technical Committee ISO/TC 159

"Ergonomics" in collaboration with Technical Committee CEN/TC 122 "Ergonomics", the

secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of

an identical text or by endorsement, at the latest by December 2006, and conflicting national

standards shall be withdrawn at the latest by December 2006.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of

the following countries are bound to implement this European Standard: Austria, Belgium,

Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,

Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice

The text of ISO 14505-3:2006 has been approved by CEN as EN ISO 14505-3:2006 without any

modifications.
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SIST EN ISO 14505-3:2006
INTERNATIONAL ISO
STANDARD 14505-3
First edition
2006-06-01
Ergonomics of the thermal
environment — Evaluation of thermal
environments in vehicles —
Part 3:
Evaluation of thermal comfort using
human subjects
Ergonomie des ambiances thermiques — Évaluation des ambiances
thermiques dans les véhicules —
Partie 3: Évaluation du confort thermique en ayant recours à des sujets
humains
Reference number
ISO 14505-3:2006(E)
ISO 2006
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
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ii © ISO 2006 – All rights reserved
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
Contents Page

Foreword............................................................................................................................................................ iv

Introduction ........................................................................................................................................................ v

1 Scope ..................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms, and definitions.......................................................................................................................... 2

4 Assessment of vehicle environments using human subjects ......................................................... 2

5 Principles of assessment..................................................................................................................... 3

5.1 Subjective methods.............................................................................................................................. 3

5.2 Objective methods................................................................................................................................ 3

5.3 Behavioural methods ........................................................................................................................... 3

5.4 Assessment of thermal comfort.......................................................................................................... 3

6 Design of human subject trials ........................................................................................................... 4

6.1 Aim of trial ............................................................................................................................................. 4

6.2 Selection of human subjects ............................................................................................................... 4

6.3 Measurement of subject responses.................................................................................................... 4

6.4 Selection of operating conditions....................................................................................................... 6

6.5 Analysis and interpretation of results ................................................................................................ 7

7 Test method for assessing thermal comfort in vehicle .................................................................... 7

Annex A (normative) Test method for assessment of vehicle thermal comfort.......................................... 8

Annex B (informative) Example of single-sheet subjective questionnaire ................................................ 10

Annex C (informative) Practical example of vehicle thermal comfort assessment using test

method ................................................................................................................................................. 11

Annex D (informative) Practical example of assessment of thermal comfort properties of vehicle

glazing.................................................................................................................................................. 13

Annex E (informative) Practical example of assessment of thermal comfort properties of vehicle

seats..................................................................................................................................................... 15

Bibliography ..................................................................................................................................................... 17

© ISO 2006 – All rights reserved iii
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 14505-3 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,

Ergonomics of the physical environment.

ISO 14505 consists of the following parts, under the general title Ergonomics of the thermal environment —

Evaluation of the thermal environment in vehicles:
⎯ Part 1: Principles and methods for assessment of thermal stress
⎯ Part 2: Determination of equivalent temperature
⎯ Part 3: Evaluation of thermal comfort using human subjects
iv © ISO 2006 – All rights reserved
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
Introduction

Direct methods for the assessment of thermal environments (hot, moderate, cold) in vehicles involve

measurements of the responses of human subjects. There are three types: subjective methods, objective

methods, and behavioural methods. Subjective methods quantify the responses of people to an environment

using subjective scales. Objective methods are those which quantify the physical, physiological or mental

condition of a person by the use of instrumentation or measures of an output such as performance measures.

Behavioural methods quantify or represent human behaviour in response to an environment. Each of these

methods has been developed according to basic principles and the most appropriate form of the method and

combination of methods used in concert for the assessment of thermal environments in vehicles will depend

upon the context and vehicle environment of interest. This part of ISO 14505 provides both principles and

application of methods for the assessment of thermal comfort in vehicle environments using human subjects.

The most appropriate methods for evaluating thermal comfort in vehicles are subjective. The principles for the

construction of subjective assessment scales are given in ISO 10551 and are used in the development of the

test method specified in this part of ISO 14505. Physiological measurements on human subjects are

described in ISO 9886 and are beyond the scope of this part of ISO 14505.

This part of ISO 14505 complements standards concerned with the ergonomics of thermal environments and

in particular can be used together with thermal indices that are valid for use in vehicle environments.

© ISO 2006 – All rights reserved v
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SIST EN ISO 14505-3:2006
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SIST EN ISO 14505-3:2006
INTERNATIONAL STANDARD ISO 14505-3:2006(E)
Ergonomics of the thermal environment — Evaluation of
thermal environments in vehicles —
Part 3:
Evaluation of thermal comfort using human subjects
1 Scope

This part of ISO 14505 gives guidelines and specifies a standard test method for the assessment, using

human subjects, of thermal comfort in vehicles. It is not restricted to any particular vehicle but provides the

general principles that allow assessment and evaluation. The method can be used to determine a measure of

the performance of a vehicle for conditions of interest, in terms of whether it provides thermal comfort to

people or not. This can be used in vehicle development and evaluation.

This part of ISO 14505 is applicable to all types of vehicles, including cars, buses, trucks, off-road vehicles,

trains, aircraft, ships, submarines, and to the cabins of cranes and similar spaces. It applies where people are

enclosed in a vehicle and when they are exposed to outside conditions. For those exposed to outside

conditions, such as riders of bicycles or motorcycles, drivers of open sports cars and operators of fork lift

trucks without cabins, vehicle speed and weather conditions can dominate responses. The principles of

assessment, however, will still apply.

This part of ISO 14505 applies to both passengers and operators of vehicles where its application does not

interfere with the safe operation of the vehicle.

It presents the principles of the assessment and evaluation of thermal comfort, including the use of test

methods and trials. It also presents subjective methods that can be used in assessment.

This part of ISO 14505 is a basic ergonomics standard which can contribute to the development of standards

concerned with specific vehicles and products.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 12894, Ergonomics of the thermal environment — Medical supervision of individuals exposed to extreme

hot or cold environments
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
© ISO 2006 – All rights reserved 1
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
3 Terms, and definitions

For the purposes of this document, the terms and definitions given in ISO 13731 and the following apply.

3.1
cold stress

climatic conditions under which the body heat exchange is just equal to, or too large for, heat balance at the

expense of significant physiological strain that sometimes cannot be compensated
3.2
equivalent temperature

temperature of a homogenous “room”, with mean radiant temperature equal to air temperature and zero air

velocity, in which a person exchanges the same heat loss by convection and radiation as in the actual

conditions
3.3
heat stress

climatic conditions under which the body heat exchange is just equal to, or too small for, heat balance at the

expense of significant physiological strain that sometimes cannot be compensated
3.4
HVAC-system
heating, ventilation and air-conditioning system of the vehicle/cabin
3.5
local equivalent temperature

temperature of a homogenous “room”, with mean radiant temperature equal to air temperature and zero air

velocity, in which a defined zone of the human body surface exchanges the same heat loss by convection and

radiation as in the actual conditions
3.6
thermal asymmetry

degree to which opposite parts of the human body are exposed to different climatic conditions

3.7
thermoneutral zone

temperature interval within which the body maintains heat balance exclusively by vasomotor reactions

4 Assessment of vehicle environments using human subjects

Although mathematical and physical models and thermal indices can provide repeatable, reliable methods of

assessment, vehicle environments are often complex, dynamic and influenced by many factors. Models and

indices are therefore often limited in validity. Human subjects are required to provide a direct means of

measuring thermal comfort and to validate other techniques. It is important, therefore, to develop assessment

methods involving human subjects. Such methods shall only be used where ethical considerations and

accepted practices involving human subjects, as provided in ISO 12894, have been carried out. They are

used for one of four main reasons:
⎯ to evaluate thermal comfort in vehicle environments;

⎯ to set up or carry out standardized test methods of thermal comfort in vehicles;

⎯ to compare measures of thermal comfort in vehicles with prediction methods (models, indices) based

upon measures of the thermal environment in vehicles;

⎯ to determine the relationship between objective measures, such as skin temperatures, and subjective

measures of thermal comfort.
2 © ISO 2006 – All rights reserved
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
5 Principles of assessment
5.1 Subjective methods

Subjective methods quantify the response of people to an environment using subjective scales. Such scales

are based upon psychological continua (or constructs) that are relevant to the psychological phenomenon of

interest. It is important to know the properties of the scales in order to correctly interpret the results. Scales of

thermal sensation (hot or cold), preference, comfort, and stickiness are often used in thermal comfort

assessment. Advantages of subjective methods are that they are simple to administer and are directly related

to the psychological phenomenon. Disadvantages are that they can interfere with what they are measuring,

some groups may not be able to perform the subjective task (for example, babies, children, people with

disabilities) and there is no reason given as to why such a response is provided. ISO 10551 should be used

for guidance on the construction of subjective scales. Five types of scales are identified. These are:

Perceptual (How do you feel now? e.g. hot); Affective (How do you find it? e.g. comfortable); Preference (How

would you prefer to be? e.g. cooler); Acceptance (acceptable/unacceptable); Tolerance (Is the environment

tolerable?). From these basic subjective dimensions, questionnaires of subjective scales can be developed.

The subjective assessment methods presented in this part of ISO 14505 are concerned with thermal comfort

and therefore do not consider “tolerance”.
5.2 Objective methods

Objective methods are those which quantify the physical or mental condition of a person by the use of

instrumentation or measures of an output such as performance measures. The principle of the method is that

the measure can be interpreted in terms of the human condition of interest (e.g. thermal comfort). An example

would be the measurement of mean skin temperature of the body that would vary with the thermoregulatory

response to heat and cold (providing a rationale for the method) and that has been shown in research to

correlate with subjective responses of comfort. Another example would be skin wetness. Disadvantages of

objective methods can be that they might interfere with what they are attempting to measure, the correlation

between the measure and thermal comfort is not perfect and that thermal comfort is a psychological

phenomenon, a condition of mind. An advantage of objective measures is that they are often independent of,

and can be used to complement, the results of other methods such as subjective measures. ISO 9886 should

be used to provide methods for measurement and interpretation of physiological strain in terms of body core

temperature, mean skin temperature, heart rate and body mass loss. Other measures, such as heart rate

variability, may also be relevant.
5.3 Behavioural methods

Behavioural methods quantify or represent human behaviour in response to an environment. The particular

aspect of human behaviour observed is related to the human condition of interest (for example, thermal

comfort in vehicles) and a method of interpretation is required. Examples would include changes in posture,

movement patterns (for example, away from uncomfortable environments), and popularity of sitting

positions(for example, if some seats were in a cold draught they would be occupied “last”). Advantages of

behavioural methods include minimum interference with what is being measured and a direct “active” measure

of discomfort. Disadvantages include the difficulty in establishing validity and reliability of the method and

direct interpretation of the results in terms of thermal comfort. For example, a change in posture could be due

to chair discomfort or other “non-thermal” reasons.
5.4 Assessment of thermal comfort

Thermal comfort assessment is most effectively carried out using subjective methods. This is because comfort

is a psychological phenomenon and a subjective rating provides a direct and quantifiable method. The simple

test method provided in this part of ISO 14505 therefore uses subjective methods. Both objective and

behavioural methods can be used to complement the test method provided, however, they would require

expert advice beyond the scope of this part of ISO 14505.
© ISO 2006 – All rights reserved 3
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)
6 Design of human subject trials
6.1 Aim of trial

The design of any vehicle test or trial using human subjects will depend upon the specific aims of that test or

trial. However, there are general principles and these are outlined below.

A typical thermal comfort trial involves driving vehicles over a route and measuring operating conditions and

thermal responses of passengers. For specific investigations, simulators are often used.

An optimum trial design will achieve its aim with efficient use of resources. To achieve this it is important to be

clear about the specific aim or aims. For example, if the aim is to compare three types of vehicle seats for

thermal comfort then a repeated measures design, where all subjects sit on all seats (in a balanced order) in

identical conditions, could provide the best comparison of the seats. Contrast this with the evaluation of a

thermal comfort index where a wide range of environmental conditions, including seats, can be optimum. If

both aims need to be met then it is essential that both types of requirement are met in the design. It is

necessary, therefore, to be specific about the aims of the trial.
6.2 Selection of human subjects

A valid method of evaluating environments would be to use a panel of experts. This technique is used in wine

tasting, for example, where acknowledged experts give opinions concerning the quality of wines. This

technique depends upon identifying unbiased acknowledged experts. This is not possible in the area of

thermal comfort and the trial designs should specifically avoid bias.

It is usual to identify a “random” sample of human subjects as representative of the population of interest. This

is a question of statistical sampling, and relevant factors such as age, gender, driving experience and

anthropometry could be identified and influence subject selection. The number of subjects selected will

depend upon the aim and experimental design. A calculation can be made based upon the power of a

statistical test; i.e. the probability of accepting the alternative hypothesis (for example, vehicle A is more

comfortable than vehicle B), given that it is true. This is a rather academic approach and requires assumptions

to be made about the strength of effect expected which is rather circular, as this is an objective of the trial. Of

practical importance will be the allocation of subjects to treatments. If there are three cars and three types of

glazing being compared (i.e. nine conditions) then nine subjects would allow a 9 × 9 Latin square design. That

is where each subject is exposed to each condition in a different, balanced, order. A repeated measures

design is where all subjects are exposed to all conditions. It is generally considered that, for normally

distributed responses, increasing the number of subjects provides a diminishing return in terms of a sample

representing a population. Numbers of eight or more are often considered as an acceptable sample size. It is

also useful to consider approximate probability. For example, if two vehicles were compared by four subjects

then the probability of all four subjects preferring vehicle A to vehicle B due to chance (when there is actually

no difference in comfort between the vehicles) is 1/2 to the power of 4 = 1/16 = 6,25 %. So four subjects would

not be sufficient to make a decision at a 5 % level even in the case of an extreme result.

An example of practical significance is whether the testers would be satisfied that if all their subjects preferred

A to B then this would be considered sufficient evidence that A is more comfortable than B. It is useful,

therefore, to estimate how many subjects it would take for practical significance to be established. It may be

that statistical significance can be established with the use of large groups of subjects, but the effect could be

small and not of practical significance. The above provides practical guidance, whereas a more rigorous

statistical approach can be taken in any particular test; nevertheless, the “rules of thumb” above can be useful.

6.3 Measurement of subject responses
6.3.1 General

The responses of the subjects that will be measured will be selected according to the aims of the trial.

Typically subjective responses are taken to quantify thermal comfort. Objective measures are sometimes

used, mainly mean skin temperature (and sometimes sweat loss), to complement subjective measures. In a

novel situation, subjective scales should be established from “first principles” by establishing subjective

4 © ISO 2006 – All rights reserved
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SIST EN ISO 14505-3:2006
ISO 14505-3:2006(E)

continua using psychological techniques. Subjective scales for assessing thermal comfort have, however,

become established. Examples are provided below. It is important to note that the way in which a scale is

presented and administered can influence results. A single-sheet questionnaire, for example, could be

preferable to a number of pages. The exact question asked should be established.

The frequency of completion of the questionnaire must be balanced with the overall experimental aim of

design. Translation of scales (from English, for example) as well as cultural aspects of the subject sample will

be issues. Knowledge of the previous ratings or of other subjects’ responses is not normally provided. Subject

training and pilot trials will be necessary. Some scales are used for ratings of overall “comfort” as well as for

areas of the body. The following scales have been developed from the guidance provided in ISO 10551.

6.3.2 Subjective scales
a) Thermal sensation scale
“Please rate on the following scale how YOU feel NOW”:
+3 Hot
+2 Warm
+1 Slightly warm
0 Neutral
−1 Slightly cool
−2 Cool
−3 Cold

This scale corresponds to the ISO sensation scale. It is useful to use the standard scales, as results can

be compared directly with International Standards asse
...

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