ISO 17488:2016

INTERNATIONAL ISO
STANDARD 17488
First edition
2016-10-01
Road vehicles — Transport
information and control systems
— Detection-response task (DRT)
for assessing attentional effects of
cognitive load in driving
Véhicules routiers — Systèmes d’Information et de commande du
transport — Tâche de Détection-Réponse (DRT) pour l’évaluation des
effets attentionnels de la charge cognitive lors de la conduite
Reference number
ISO 17488:2016(E)
©
ISO 2016

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ISO 17488:2016(E)

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© ISO 2016, Published in Switzerland
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ISO 17488:2016(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 5
5 DRT methodology: Principles and overview . 5
6 Measurement methods and procedures . 6
6.1 Participants . 6
6.2 Experimental setup . 6
6.2.1 Non-driving experimental setup . 6
6.2.2 Surrogate driving experimental setup . 6
6.2.3 Driving simulator experimental setup . 6
6.2.4 On-road experimental setup . 6
6.3 Stimulus presentation. 6
6.3.1 Stimulus presentation timing . 7
6.3.2 Visual stimulus specifications . 8
6.4 Response method .10
6.5 Primary driving task .11
6.6 Instructions to participants .11
6.7 Training procedure .11
6.7.1 Secondary task training .12
6.7.2 DRT training .12
6.7.3 Primary task training .12
6.7.4 Training on multitasking .12
6.8 Performance measures .12
6.9 Analysing and interpreting DRT performance data .13
6.10 Checking data quality .13
6.11 Use of DRT data in decision making .14
Annex A (normative) Rationale .15
Annex B (normative) Guidelines for selecting between variants of the DRT method .23
Annex C (normative) Additional factors affecting DRT performance .25
Annex D (informative) DRT variants .27
Annex E (informative) Summary of results from the ISO-coordinated studies .38
Bibliography .69
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ISO 17488:2016(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.
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 on 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 the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 39,
Ergonomics.
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ISO 17488:2016(E)

Introduction
Driving is a complex task consisting of a range of sub-tasks such as keeping the vehicle in the lane,
avoiding other traffic and obstacles, observing road signs and signals, planning and initiating specific
manoeuvres, scanning mirrors and navigating. In addition, drivers often engage in secondary tasks, not
directly related to driving, such as operating the media player, conversing on the phone and reading
road-side commercial signs.
These different activities place varying, and sometimes conflicting, demands on the driver. In order to
manage the various driving and secondary tasks, the driver thus needs to allocate different resources,
such as the eyes, hands, feet, perceptual systems, motor control systems and higher level cognitive
functions, to the different sub-tasks in a dynamic and flexible way. This allocation of resources to
driving and non-driving activities may be generally conceptualized as driver attention. In most driving
situations, attention is determined by an interaction of proactive (top-down, endogenous) processes
based on anticipation of how the upcoming situation will develop and bottom-up processes (driven by
exogenous stimuli) which can trigger attention to the situation when it does not develop as expected,
even leading to a corrective action.
There is a need for methods that can be used to assess how engagement in secondary tasks affects driver
attention. In general, the effect of a task on attention depends on the amount and type of resources
demanded by the task. As outlined in further detail in Annex A, resources can be conceptualized at
three general levels: sensory-actuator resources, perceptual-motor resources and cognitive resources.
Sensory/actuator resources refer to the basic interfaces between the driver and the environment used
to sense the environment and perform overt actions. Examples include the eyes, the ears, the skin, the
feet, the hands, the mouth, the vocal cords, etc. Perceptual/motor resources can be regarded as brain
functions for controlling specific perceptual-motor activities, e.g. visual perception, manual tracking
and hand-to-eye coordination. Finally, cognitive resources refer to brain systems implementing higher-
level cognitive operations such as planning, decision making, error detection, sustaining information
in working memory, dealing with novel or difficult situations and overcoming habitual actions. These
types of high-level cognitive functions may be conceptualized in terms of cognitive control. While
sensory-actuator and perceptual-motor resources are, at least to some extent, modality-specific,
cognitive control can be regarded as a single resource with strongly limited capacity, not associated
with any particular sensory modality. Cognitive load thus refers specifically to the demand for cognitive
control that a task imposes on the driver.
Several existing and draft ISO standards address the assessment of secondary task demand in the
[1] [2]
context of driving. ISO 15007-1 and ISO/TS 15007-2 provide guidance on how to measure glance
[3]
behaviour and ISO 16673 focuses exclusively on the viewing time required to perform a task using an
in-vehicle information system. Hence, these methods focus mainly on the assessment of (visual) sensory
[4]
demand (i.e. the demand for the eyes). ISO 26022 provides a technique for evaluating the combined
effect of sensory-actuator, perceptual-motor and cognitive demands on a driver’s performance in a
combined event detection and vehicle control task.
However, a standardized measurement method that specifically addresses cognitive load is lacking.
While, for example, ISO 26022 is sensitive to cognitive load, it lacks specificity since its main
performance metric (MDEV) is also sensitive to visual sensory motor interference (i.e. visual time
sharing; see Annex A). A standardized method specifically addressing cognitive load is particularly
needed in order to evaluate the attentional demands of new driver-vehicle interfaces designed to
minimize visual interaction such as voice-based interfaces, haptic input devices and head-up displays.
The detection-response task (DRT) method defined in this document intends to fill this gap. More
specifically, the DRT is mainly intended to measure effects of the cognitive load of a secondary task on
attention. However, some versions of the DRT specified in this document may also be used to capture
other forms of secondary task demand (e.g. visual sensory demand). The general rationale behind the
DRT methodology is further outlined in Annex A.
Annex B provides guidance on how to select among the different DRT versions defined in this
document. Annex C reviews factors that could potentially affect DRT performance and thus need to be
accounted for when designing DRT experiments. Annex D offers a review of existing alternative DRT
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ISO 17488:2016(E)

methodologies not covered by this document. Annex E provides an overview of the results from a set of
coordinated studies with the purpose to support the development of this document. Finally, a general
bibliography is provided for existing DRT-related research.
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INTERNATIONAL STANDARD ISO 17488:2016(E)
Road vehicles — Transport information and control
systems — Detection-response task (DRT) for assessing
attentional effects of cognitive load in driving
1 Scope
This document provides a detection-response task mainly intended for assessing the attentional effects
of cognitive load on attention for secondary tasks involving interaction with visual-manual, voice-
based or haptic interfaces. Although this document focuses on the assessment of attentional effects of
cognitive load (see Annex A), other effects of secondary task load may be captured by specific versions of
the DRT, as further outlined in Annex B. Secondary tasks are those that may be performed while driving
but are not concerned with the momentary real-time control of the vehicle (such as operating the media
player, conversing on the phone, reading road-side commercial signs and entering a destination on the
navigation system).
NOTE According to this definition, secondary tasks can still be driving-related (such as in the case of
destination entry).
This document does not apply to the measurement of primary (driving) task demands related to
the momentary real-time control of the vehicle, such as maintaining lane position and headway or
responding to forward collision warnings. However, this does not preclude that the DRT method, as
specified in this document, may be adapted to measure such effects.
This document applies to both original equipment manufacturer (OEM) and after-market in-vehicle
systems and to permanently installed, as well as portable, systems.
It is emphasized that, while the DRT methodology defined in this document is intended to measure the
attentional effects of cognitive load, it does not imply a direct relationship between such effects and
crash risk. For example, taking the eyes off the road for several seconds in order to watch a pedestrian
may not be very cognitively loading but could still be expected to strongly increase crash risk.
Furthermore, interpret DRT results cautiously in terms of demands on a specific resource, such as
cognitive load. Specifically, if the goal is to isolate the effect related to the cognitive load imposed by a
secondary task on attention, avoid overlap with other resources required by the DRT (e.g. perceptual,
motor, sensory or actuator resources). A particular concern derives from the fact that the DRT utilizes
manual responses (button presses). Thus, for secondary tasks with very frequent manual inputs (on
the order of one or more inputs per second), increased response times on the DRT may reflect this
specific response conflict (which is due to the nature of the DRT) rather than the actual cognitive
load demanded by the task when performed without the DRT (i.e. alone or during normal driving;
see Annex E). Thus, for such response-intensive tasks, DRT results are interpreted with caution. This
document defines three versions of the DRT and the choice of version depends critically on the purpose
of the study and the conditions under which it is conducted (see Annexes A and B for further guidance
on this topic).
This document specifically aims to specify the detection-response task and the associated measurement
procedures. Thus, in order to be applicable to a wide range of experimental situations, this document
does not define specific experimental protocols or methods for statistical analysis. However, some
guidance, as well as examples of established practice in applying the DRT, can be found both in the main
body of this document and in the annexes (in particular Annexes C and E).
2 Normative references
There are no normative references in this document.
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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:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
actuator demand
demand for actuator resources (3.2) imposed by a task (3.30)
3.2
actuator resources
human body systems used to execute overt motor actions
Note 1 to entry: Examples of actuator resources include the hands, the feet, the vocal cords, etc.
3.3
attention
allocation of resources, encompassing both bottom up and top down attentional processes, to a
particular activity or activities
3.4
cognitive control
mental operations such as planning, decision making, error detection, inhibiting habitual actions,
utilizing information in working memory (3.36), and resolving novel and complex situations
3.5
cognitive resources
brain systems implementing cognitive control (3.4)
3.6
cognitive load
cognitive demand
demand for cognitive control (3.4) imposed by a task (3.30)
3.7
data segment
continuous portion of data
3.8
driver attention
allocation of resources (3.20), encompassing both bottom up and top down attentional processes, to
driving and/or non-driving-related activities
3.9
DRT stimulus
sensory signal controlled and issued to a participant during a DRT test session for the purpose of
eliciting a specified response (3.21)
3.10
hit
response (3.21) initiated within 100 ms to 2 500 ms from the stimulus onset (3.29), not preceded by an
earlier response in the same interval
Note 1 to entry: Hit is synonymous with valid response.
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3.11
hit rate
number of valid responses (3.33) divided by the total number of stimuli presented in a data collection
segment, excluding premature responses to stimuli
Note 1 to entry: See premature response (3.17).
3.12
missing response
absence of a response (3.21) within 100 ms to 2 500 ms after stimulus onset (3.29)
3.13
motor demand
demand for motor resources (3.13) imposed by a task (3.30)
3.14
motor resources
brain systems implementing the control of motor actions
3.15
perceptual demand
demand on perceptual resources (3.15) imposed by a task (3.30)
3.16
perceptual resources
brain systems implementing perception
Note 1 to entry: Perceptual functions include lower-level, modality-specific perception (e.g. visual and auditory
perception), as well as higher-level cross-modal perceptual integration.
3.17
premature response
response (3.21) initiated within 100 ms from the stimulus onset (3.29), prior to the timing interval for a
valid response (3.33)
3.18
primary task
driving or driving-like task (3.30) used in the surrogate driving, driving simulator or on-road DRT
experimental setups
3.19
repeated response
response (3.21) initiated within 100 ms to 2 500 ms after the stimulus onset (3.29) that is preceded by
an earlier response in the same interval
3.20
resources
systems in the brain or body that can be utilized to perform tasks (3.30)
3.21
response
signal generated by the participant pressing the response button
3.22
response time
time from the stimulus onset (3.29) until the response onset
Note 1 to entry: Response time is only defined for valid responses.
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3.23
secondary task
task (3.30) that may be performed while driving but that is not concerned with the momentary real-
time control of the vehicle
Note 1 to entry: Examples include operating the media player, conversing on the phone, reading road-side
commercial signs and entering a destination on the navigation system. Thus, secondary tasks may be driving-
related.
3.24
sensory demand
demand on sensory resources (3.24) imposed by a task (3.30)
3.25
sensory resources
human body systems used to sense the exterior environment or internal bodily states
Note 1 to entry: Examples of sensory resources include the eyes, the ears, the skin, etc.
3.26
stimulus duration
time during which the stimulus is turned on
Note 1 to entry: The maximum stimulus duration is set at 1 s.
Note 2 to entry: Stimulus duration depends on responses. The maximum stimulus duration represents the pre-
set duration of the stimulus in the absence of a response. If the response is initiated prior to maximum stimulus
duration, the stimulus is turned off.
3.27
stimulus cycle period
time from the onset of a stimulus until the onset of the next stimulus
3.28
stimulus offset
point in time when the DRT stimulus (3.9) is turned off
3.29
stimulus onset
point in time when the DRT stimulus (3.9) is turned on
3.30
task
process of achieving a specific and measurable goal using a prescribed method
3.31
trial
test of one participant undertaking one secondary task (3.23) one time
3.32
unrequested response
response (3.21) given later than 2 500 ms after the stimulus onset (3.29)
3.33
valid response
response (3.21) initiated within 100 ms to 2 500 ms from the stimulus onset (3.29), not preceded by an
earlier response in the same interval
Note 1 to entry: Valid response is synonymous with hit.
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3.34
visual angle
angle subtended at the eye by a viewed object or separation between viewed objects
Note 1 to entry: Measurement of visual angle is made edge to edge.
3.35
visual eccentricity
visual angle (3.34), relative to the centre of the fovea, at which a certain visual stimulus impinges on
the retina
Note 1 to entry: Measurement of visual eccentricity is made from centre of eye to centre of visual stimulus.
3.36
working memory
executive and attentional aspect of short-term memory involved in the interim integration, processing,
disposal and retrieval of information
4 Abbreviated terms
ANOVA analysis of variance
B baseline
DRT detection-response task
HDRT head-mounted DRT
HR hit rate
MR miss rate
N0 0-Back
N1 1-Back
OEM original equipment manufacturer
R response
RT response time
RDRT remote DRT
SE easy SuRT
SH hard SuRT
TDRT tactile DRT
5 DRT methodology: Principles and overview
The DRT method is based on a simple detection-response task where participants respond to relatively
frequent artificial stimuli presented with a specified degree of temporal uncertainty. Detection
performance, measured in terms of response time and hit rate, is assumed to represent the degree to
which attention is affected by the demand and, in particular, the cognitive load component imposed
by the secondary task under evaluation. Longer reaction times and reduced hit rate are indicative of
higher cognitive load.
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The method may be implemented in several different ways, depending on the purpose of the study.
The DRT versions specified by this document differ in terms of stimulus presentation modality and
experimental setup, as further described below.
6 Measurement methods and procedures
6.1 Participants
Participants should be licensed drivers with a similar level of prior experience with the secondary task
under evaluation. Other relevant characteristics of the participants shall be recorded, including at least
driving experience (e.g. miles or km driven in the last year), similar device use experience, gender, age
and previous experience with the DRT.
6.2 Experimental setup
The DRT may be used in different experimental setups as described below.
6.2.1 Non-driving experimental setup
In this setup, the DRT is performed concurrently with the secondary task under evaluation in a non-
driving situation. This means that attention is divided between the secondary task under evaluation
and the DRT, without simultaneous performance of a primary (driving or driving-like) task. DRT
performance with the secondary task is assessed relative to a baseline condition where only the DRT
is performed. The non-driving version of the DRT may be used to assess how a secondary task affects
selective attention in any non-driving setting, including production vehicles, vehicle mock-ups or at a
desktop.
6.2.2 Surrogate driving experimental setup
In this setup, the DRT is performed concurrently with the secondary task under evaluation while the
participant performs a surrogate task that functions as the primary task of driving. This surrogate
task could be a simple tracking task, watching a video of real-world driving recorded from the driver’s
viewpoint or a combination of such elements. DRT performance during the combined secondary task
and surrogate driving is assessed relative to a baseline condition where the DRT is performed with only
the surrogate driving task.
6.2.3 Driving simulator experimental setup
In this setup, the DRT is performed concurrently with the secondary task under evaluation while the
participant drives a driving simulator. DRT performance during the combined secondary task and
simulator driving is assessed relative to a baseline condition where the DRT is performed while only
driving the simulator. The same scenario is used in both conditions.
6.2.4 On-road experimental setup
In this setup, the DRT is performed concurrently with the secondary task under evaluation while the
participant drives on a closed track or an open road with traffic. Appropriate safety concerns shall be
addressed for on-road testing. DRT performance during the combined secondary task and driving is
assessed relative to a baseline condition where the DRT is performed while only driving.
6.3 Stimulus presentation
This document specifies three alternative methods for presenting the DRT stimulus. This includes two
methods where the stimulus is presented visually and one method where the stimulus is provided by
means of tactile stimulation. In the head-mounted DRT (HDRT), a visual stimulus (an LED) is presented
through a fixture attached to the head of the participant at a specified visual angle. In the remote
DRT (RDRT), a visual stimulus (e.g. an LED or embedded graphic in simulator scenario) is presented
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in the forward view of the participant. Finally, in the tactile DRT (TDRT), a tactile vibrator is placed
on the participant’s body. These stimulus presentation methods are described in further detail below.
Guidelines for the selection of stimulus presentation mode depend on the purpose of the experiment
and are provided in Annex B.
6.3.1 Stimulus presentation timing
The stimulus presentation timing is the same for all three stimul
...