Road vehicles — Ergonomic aspects of in-vehicle presentation for transport information and control systems — Warning systems

ISO/TR 16352:2005 provides a literature survey about the human-machine interface of warning systems in vehicles. It covers the experimental experiences about the efficiency and acceptance of different modalities and combinations of warnings, and the design of the sensorial, code and organizational parameters of visual, auditory and tactile warnings.

Véhicules routiers — Aspects ergonomiques de la présentation des systèmes de commande et d'information des transports à l'intérieur des véhicules — Systèmes avertisseurs

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Publication Date
21-Nov-2005
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6060 - International Standard published
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30-Apr-2006
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22-Nov-2005
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TECHNICAL ISO/TR
REPORT 16352
First edition
2005-12-01
Road vehicles — Ergonomic aspects
of in-vehicle presentation for transport
information and control systems —
Warning systems
Véhicules routiers — Aspects ergonomiques de la présentation des
systèmes de commande et d'information des transports à l'intérieur des
véhicules — Systèmes avertisseurs
Reference number
ISO/TR 16352:2005(E)
ISO 2005
---------------------- Page: 1 ----------------------
ISO/TR 16352:2005(E)
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ii © ISO 2005 – All rights reserved
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ISO/TR 16352:2005(E)
Contents Page

Foreword............................................................................................................................................................. v

Introduction ....................................................................................................................................................... vi

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

2 Warning signals.................................................................................................................................... 2

2.1 Criteria of warning effects ................................................................................................................... 2

2.2 Categorization of warning signal failure ............................................................................................ 4

2.3 Urgency mapping.................................................................................................................................. 6

2.4 Alarm theories....................................................................................................................................... 8

2.5 Design recommendations.................................................................................................................. 10

3 Psychological and physiological aspects........................................................................................ 10

3.1 Human processing of warnings ........................................................................................................ 10

3.2 Workload.............................................................................................................................................. 12

3.3 Expectancy.......................................................................................................................................... 13

3.4 Further human factors, individual differences ................................................................................ 13

3.5 Recommendations.............................................................................................................................. 14

4 Sensorial modality.............................................................................................................................. 15

5 Visual warning signals ....................................................................................................................... 17

5.1 Psychological/physiological bases.................................................................................................. 18

5.2 Types of visual displays .................................................................................................................... 19

5.3 Design parameters.............................................................................................................................. 20

5.3.1 Sensorial-related parameters............................................................................................................ 20

5.3.2 Coding parameters............................................................................................................................. 24

5.3.3 Organizational parameters................................................................................................................ 37

6 Auditory warnings .............................................................................................................................. 39

6.1 Psychological/physiological bases.................................................................................................. 40

6.2 Advantages of auditory presentation ............................................................................................... 41

6.3 Tonal signals, auditory icons ............................................................................................................ 42

6.3.1 Advantages of tonal signals .............................................................................................................. 42

6.3.2 Standards............................................................................................................................................ 42

6.3.3 Attributes............................................................................................................................................. 42

6.3.4 Sensorial parameters......................................................................................................................... 44

6.3.5 Coding parameters............................................................................................................................. 47

6.3.6 Organizational parameters................................................................................................................ 54

6.4 Speech output..................................................................................................................................... 55

6.4.1 Advantages of speech output ........................................................................................................... 56

6.4.2 Sensorial-related parameters............................................................................................................ 56

6.4.3 Coding parameters............................................................................................................................. 60

6.4.4 Organizational parameters................................................................................................................ 63

6.4.5 Warning applications of speech output ........................................................................................... 65

6.5 Comparison of tonal signals and speech output ............................................................................ 66

7 Tactile warnings.................................................................................................................................. 68

7.1 Advantages of tactile presentation................................................................................................... 68

7.2 Design parameters.............................................................................................................................. 70

7.2.1 Sensorial-related parameters............................................................................................................ 70

7.2.2 Coding parameters............................................................................................................................. 71

8 Redundancy of message presentation............................................................................................. 71

8.1 Visual/auditory combination.............................................................................................................. 72

8.2 Visual/auditory qualities for in-vehicle displays ............................................................................. 73

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ISO/TR 16352:2005(E)

8.3 Visual/auditory indications for displays ........................................................................................... 74

8.4 Visual/auditory/tactile combination .................................................................................................. 74

8.5 Master alerting..................................................................................................................................... 75

8.6 Other concepts.................................................................................................................................... 75

9 Comparison of warning types, codes and modalities..................................................................... 77

9.1 Visual/auditory presentation of non-verbally-coded objects ......................................................... 77

9.2 Visual/auditory presentation of verbally-coded objects/abstract information............................. 78

9.3 Visual/auditory presentation of verbally-/non-verbally-coded spatial information...................... 79

9.4 Visual presentation of non-verbally-coded information/auditory presentation of verbally-

coded information............................................................................................................................... 81

9.5 Visual/tactile presentation of non-verbally-coded objects/spatial information............................ 82

9.6 Auditory/tactile presentation of non-verbally-coded objects/spatial information ....................... 85

9.7 Visual/auditory/tactile presentation of verbally-coded objects/abstract information.................. 86

9.8 Recommendations for warning systems.......................................................................................... 86

10 Warnings in assistance systems....................................................................................................... 88

10.1 Distance warning systems................................................................................................................. 91

10.2 Collision warning systems................................................................................................................. 92

10.3 Side-obstacle warning systems......................................................................................................... 98

10.4 Lane-departure warning systems.................................................................................................... 100

10.5 Manoeuvring aids for low speed operation.................................................................................... 102

10.6 Usability of intelligent-transport-systems information for drivers .............................................. 104

10.7 Other assistance systems................................................................................................................ 104

11 Warnings in other applications........................................................................................................ 105

11.1 Aircraft................................................................................................................................................ 105

11.2 Intensive care unit............................................................................................................................. 106

11.3 Industrial plants ................................................................................................................................ 106

12 Discussion......................................................................................................................................... 108

13 Summary............................................................................................................................................ 110

13.1 Introduction ....................................................................................................................................... 110

13.2 Warning signals................................................................................................................................ 110

13.3 Psychological and physiological aspects, sensorial modality .................................................... 111

13.4 Visual warning signals ..................................................................................................................... 111

13.5 Auditory warnings............................................................................................................................. 113

13.6 Tactile warnings................................................................................................................................ 115

13.7 Redundancy of message presentation ........................................................................................... 116

13.8 Comparison of warning types, codes and modalities................................................................... 116

13.9 Warnings in assistance systems..................................................................................................... 117

13.10 Warning in other applications.......................................................................................................... 118

Bibliography ................................................................................................................................................... 119

iv © ISO 2005 – All rights reserved
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ISO/TR 16352:2005(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.

In exceptional circumstances, when a technical committee has collected data of a different kind from that

which is normally published as an International Standard (“state of the art”, for example), it may decide by a

simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely

informative in nature and does not have to be reviewed until the data it provides are considered to be no

longer valid or useful.

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/TR 16352 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 13,

Ergonomics applicable to road vehicles.
© ISO 2005 – All rights reserved v
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ISO/TR 16352:2005(E)
Introduction

From a task/function analytic perspective, the task of driving is composed of three major interlinked categories

of activity (Hancock and Parasuraman, 1992):
a) vehicle control;
b) navigation;
c) collision avoidance.

Each of these functions contribute to the overall workload imposed on the driver. Even under routine, low-

traffic conditions, the driver must co-ordinate several tasks together and, generally, can do so quite efficiently.

Many of these task components become highly automatized with practice, so that under normal driving

conditions the demands of divided attention on the drivers will generally be within the limits of their attentional

capacity. However, during more demanding traffic situations, for example, when traffic density increases or at

intersections or traffic roundabouts, divided attention demands may sometimes exceed a driver's capabilities.

The driver has to deal with a lot of information which has different situation-dependent priorities and which is

more or less expected by the driver. Highly demanding situations are characterized by high time and spatial

density or by an extended spatial range of information. Parts of the information are natural and parts are

coded within or outside the vehicle. While receiving, processing and reacting to the information, the driver can

be overtaxed, which results in critical driving situations with increased accident probability.

This is the motivation to support the driver with assistance systems. The degree of assistance available

seems likely to increase considerably over the coming years. Assistance systems can, for example, control

speed and distance between vehicles and vehicle position in relation to the road. They not only aim to

optimize driver strain and increase driving safety, but also to achieve maximum driver acceptance. For

example, the S.A.N.T.O.S system is a (adaptive) driver-assistance system which integrates systems like

active cruise control (ACC), heading control (HC), navigation, telephone and radio (Weiße et al., 2002).

Most of these assistance systems announce any abnormal or dangerous state of the car or the driving

environment to the driver and require a relatively quick reaction by the driver. These systems warn the driver

and convey an appropriate message to the driver. So, with an increasing number of assistance systems, more

respective warnings are expected. These warnings need to be designed individually and with respect to their

interrelation.
vi © ISO 2005 – All rights reserved
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TECHNICAL REPORT ISO/TR 16352:2005(E)
Road vehicles — Ergonomic aspects of in-vehicle presentation
for transport information and control systems — Warning
systems
1 Scope

This Technical Report provides a literature survey about the human-machine interface of warning systems in

vehicles, including studies of ISO/TC 22/SC 13/WG 8 and ISO/TC 204/WG 14. It covers the experimental

experiences about the efficiency and acceptance of different modalities and combinations of warnings, and

the design of the sensorial, code and organizational parameters of visual, auditory and tactile warnings (as

well as concluding recommendations). The survey should initialize standardizing activities of ISO working

groups, e.g. ISO/TC 22/SC 13/WG 8.

This literature survey comprises the human-machine interface issues of warning systems in automobiles. The

discussion of warning signals in general is dealt with in Clause 2 and concerns the definition of warning

signals, their failure and urgency aspects. Alarm theories are briefly dealt with here. The basic psychological

and physiological aspects of warnings in vehicles are the subject of Clause 3. Some issues of human

behaviour, which are relevant to handling warnings, are described.

Due to their importance, the sensorial modalities are introduced separately in Clause 4. Auditory and tactile

presentations are becoming more and more important, which is reflected in the structure of the next three

Clauses 5, 6 and 7. The specific psychological and physiological bases, benefits and types of displays for

each sensory modality are presented in these clauses. Clause 5 is dedicated to visual warning displays with a

few examples of the sensorial-related parameters. Symbols, icons and text are discussed extensively. Other

coding and organizational features are handled as far as warning signals are affected (colour, blinking,

structures, etc.).

Clause 6 is dedicated to auditory warning displays. The basic differences and the respective benefits of tonal

signals, auditory icons and speech output are explained. This is the largest clause because of its significance

for oncoming information and warning systems in cars. The display parameters, which are particularly relevant

for auditory warning signals, are presented in more detail, i.e. startling effect, temporal and spatial

characteristics. The new auditory icons are elaborated more in detail because of their relevance for collision

warning systems. The sensorial, coding and organizational parameters of speech output are described in a

comprehensive manner.

Clause 7 is dedicated to tactile warning displays. Although the potential of tactile warnings has been clearly

demonstrated, data for their design is very scarce.

The redundant presentation of warnings is described in Clause 8. The experimental results of different

visual/auditory combinations are presented, as well as visual/auditory/tactile combinations. The possible

transfer of master alertings from the avionic environment into the automobile environment is discussed. Other

concepts like the graded sequence of warnings are included.

The experimental results with different warning signals and their combinations are presented in Clause 9 with

respect to type, code and modality of the warnings. The benefits of visual, auditory and tactile warnings

depend on whether objects, spatial relations or abstract information are transmitted verbally or non-verbally. A

series of field experiments with symbolic, written, tonal, spoken and tactile warnings are reported.

Clause 10 includes some of the assistance systems that have just been introduced, such as distance warning

systems, or that are about to be introduced, such as side-obstacle warning systems. All of these are relatively

time-critical and need carefully designed warnings with a particular emphasis on auditory and tactile displays.

The recent experimental results are cited.
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ISO/TR 16352:2005(E)

In Clause 11, warning systems in other domains, especially avionics, are described. The extensive

experiences with the problems of several time-critical alarms in aircrafts as well as the flood of alarms in

power plants will be exemplified.

Clause 12 is dedicated to the discussion of the previous clauses and their relevance for warnings in vehicles.

Drivers are assisted in highly demanding driving situations by technical systems. There will be

more assistance systems in the near future with appropriate warnings for the driver. Not all

warnings will be a priori appropriate. Guidance from this study will help ensure they are

“appropriate”. The scope of this Technical Report is to survey the literature about the human-

machine interface of warning systems. It includes papers about the efficiency and acceptance of

different modalities and combinations of warnings and the design of the sensorial, coding and

organizational parameters of visual, auditory and tactile warnings.
2 Warning signals
2.1 Criteria of warning effects

The word “warning” implies a range of levels from simple situation indications to more imperative warnings

and commands directed toward the driver to perform a certain task (ISO/TC 204/WG 14, Komoda and Goudy,

1995).
There are several technical processing stages of warnings (Kopf, 1998):
⎯ detection of object, reading of sensor data, filtering;
⎯ recognition of situation;
⎯ evaluation of situation;
⎯ output of warning.

Warnings are designed to provide someone, exposed to that product or situation, with information in addition

to that which that person could reasonably be expected to possess. The designer is trying in some way to

influence the behaviour of the recipient of the warning. This could mean preventing someone from doing

something that he or she otherwise might have done, or it could mean getting him or her to do something that

might otherwise have been omitted. The receiver of the warning then has the task of deciding whether the

advantages in complying with the warning outweigh the costs of doing so.

An emergency signal paradigm is usually one where two components are operating in tandem. The first

component consists of a mechanical device that uses sensor logic to determine if and when to trigger a signal

(Getty et al., 1995). It involves proper setting of the sensor decision threshold. If the criterion is set too strictly,

false signals will be minimized, but there is the possibility that dangerous situations will go unsignalled. If the

criterion is set too leniently, fewer dangerous situations will go unsignalled (missed signals), but the false

signal rate will rise. The solution to this dilemma requires designing the physical components of the system to

optimize the trade-off between minimized false signals and maximized sensitivity.

The second component of an emergency signal response paradigm is the human operator, who is responsible

for detecting, evaluating and responding (or not responding) to the signal that is generated by the sensor-

based signalling system. Consideration of the second component is necessarily a more complex process than

manipulating the first component, due to the cognitive and perceptual processes of the human operator.

One has to differentiate between behaviour that occurs naturally in the relevant situation without a warning

necessarily being present, and the ‘added value’ that the warning might bring. The particular effect the

warning will have has to be known, so that the relative effects of different warning variables on compliance

can be assessed. The distinction between amount of compliance with and without the warning is crucial.

2 © ISO 2005 – All rights reserved
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ISO/TR 16352:2005(E)

Warnings are artefacts. They are representations of the situations to which they refer. Most warnings serve

two functions: the alerting function and the informing function. The alerting function is somewhat abstract,

being emotive or motivational or both. The informing function is more explicit. For example, an auditory

warning may be overwhelmingly alerting, but contain no information at all beyond the fact that something has

gone wrong. Vice versa, a warning text may contain a minimal alerting effect, but may contain lots of

information.

Also relevant is the knowledge of the situation in which the warning occurs. Together the factors that have an

alerting function can be seen as the iconic aspects of warning. Such aspects act almost instantaneously and

require little conscious information processing. Generally one of the aims of a warning is to produce a rapid

alerting response which is appropriate to the product or situation. The alerting function results from more than

just, for example, the signal word, but results from the entire warning-in-context.

A warning is rated information (Kopf, 1998). A good warning should include:
⎯ an element which attracts the attention;
⎯ a reason for the warning;
⎯ the consequences if the warning is not observed;
⎯ instruction for actions.
There are different false warnings (Kopf, 1998, see 2.2):
⎯ time-dependent false warning: too early, too late;
⎯ logical false warning: no warning in critical situation and vice versa;
⎯ qualitative false warning: too many, too few, too strong, too weak.

Figure 1 shows the remaining time as a function of time when the warning is successful, not necessary or too

late, which results in an accident, depending on the moment of the driver's reaction.

To test the efficiency and impairment of warning systems, the following aspects have to be considered (Breuer

et al., 1994):
⎯ impairment (e.g. startling effect);
⎯ reliable detection and identification (conspicuousness, clearness);
⎯ transformation in safe behaviour.
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ISO/TR 16352:2005(E)
Key
X time
Y remaining time
1 time of warning
2 driver's reaction
3 unnecessary warning
4 successful warning
5 accident
Figure 1 — Time aspects of warning (Kopf, 1998)
2.2 Categorization of warning signal failure

Pritchett (1997) investigated the pilot's non-conformance to alerting systems (see 11.1). Pilot´s non-

conformance changes the final behaviour of the system and therefore may reduce actual performance from

that anticipated.
The pil
...

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