ISO 16673:2017

INTERNATIONAL ISO
STANDARD 16673
Second edition
2017-09
Road vehicles — Ergonomic aspects
of transport information and control
systems — Occlusion method to assess
visual demand due to the use of in-
vehicle systems
Véhicules routiers — Aspects ergonomiques des systèmes
d'information et de contrôle du transport — Méthode par occlusion
pour évaluer la distraction visuelle due à l'utilisation des systèmes
embarqués
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement procedures . 4
4.1 Set-up . 4
4.2 Vision and occlusion intervals . 4
4.3 Task timing . 5
4.4 Exclusion of trials . 6
5 Assessing visual demand . 6
5.1 Selection of tasks . 6
5.2 Participants . 6
5.3 Training . 6
5.4 Test trials . 7
5.5 Experimental plan . 7
5.6 Calculation of visual demand metrics . 8
5.6.1 General. 8
5.6.2 Calculating TSOT . 8
5.6.3 Calculating R . 9
5.6.4 Interpretation of results .10
Annex A (informative) System response delay .11
Annex B (informative) Surrogate driving task as a primary task .14
Bibliography .15
Foreword
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 39,
Ergonomics.
This second edition cancels and replaces the first edition (ISO 16673:2007), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the accessibility has been changed from “unrestrained driver” to “buckled driver” in 3.1;
— the following paragraph has been added in 4.1: “Written instructions should not be visible to the
participants during task performance or they should be visible to the participants during the whole
task performance, i.e. also during occluded intervals”;
— Annex B has been added.
iv © ISO 2017 – All rights reserved

Introduction
A wide range of information and communication devices and advanced driver assistance systems are
being introduced into motor vehicles. These include navigation aids, emergency messaging systems and
wireless communication including email and internet access, which are all accessible to the driver of
a motor vehicle. Many of these features have associated visual information that can potentially both
inform and distract. To help ensure that the use of such devices and features that are meant to be
used by the driver while driving do not result in excessive visual demand, a consistent, verifiable and
repeatable method to determine the visual demand imposed by such in-vehicle systems is needed.
Developing precise mathematical predictions of the risk of a crash due to driver distraction from
using a particular driver interface is difficult. However, it can be reasonably stated that if drivers are
not looking at the road (e.g. looking inside the vehicle to operate a control or read a display), then the
[5]
probability of a crash is increased .
This document is not intended to preclude direct measurement of eye glances as a method to assess
visual demand. Direct measurement of eye glances is always desirable. However, direct measurements
of eyes-off-the-road times, i.e. glance time measurements, are typically difficult and very costly to
measure. The occlusion method estimates visual demand, including resumability, of a task using a
means for intermittent viewing of the in-vehicle system. Evaluation by occlusion identifies driver
interfaces that are likely to take the driver’s eyes away from the road for excessively long durations.
Additional data collected without occlusion can be combined with occlusion data to calculate R, a
measure believed to identify whether or not tasks can be easily resumed after the driver interrupts the
task to look back at the road. This procedure does not require extensive resources and can be applied if
a functioning prototype of the driver interface exists.
INTERNATIONAL STANDARD ISO 16673:2017(E)
Road vehicles — Ergonomic aspects of transport
information and control systems — Occlusion method to
assess visual demand due to the use of in-vehicle systems
1 Scope
This document provides a procedure for measuring visual demand due to the use of visual or visual-
manual interfaces accessible to the driver while the vehicle is in motion. It applies to both original
equipment manufacturer (OEM) and after-market in-vehicle systems. It applies to both permanently
installed and portable systems. It applies to any means of visual occlusion and is not dependent on one
specific physical implementation.
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:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
driver accessible
interface controls necessary to complete the task (3.11) that are within the reach of the buckled driver
and the interface display is visible with a head movement, and the system is operable by the driver
[1] [3]
Note 1 to entry: See ISO 3958 for the driver reach of the restrained driver, and SAE J1050 for the head
movement.
Note 2 to entry: The driver interface includes the visual display and any relevant controls.
EXAMPLE A nomadic or portable device such as a PDA outside of the reach of a restrained driver is still
considered driver accessible if within the reach envelope of a buckled driver.
3.2
glance duration
time from the moment at which the direction of gaze moves towards a target (e.g. the interface display)
to the moment it moves away from the target
Note 1 to entry: This includes the transition time to that target as shown in Figure 1, simplified from
[2]
ISO 15007-1:2014, Figure A.2 .
Note 2 to entry: A single glance duration may also be referred to as a glance.
Key
X time
1 target B (e.g. the interior mirror)
2 target A (e.g. the roadway)
3 target C (e.g. in-vehicle display)
a
Glance duration.
Figure 1 — Chronological relationship of driver visual allocation between target regions
3.3
goal
system end state sought by the driver and which is meaningful in the context of a driver’s use of an in-
vehicle system
EXAMPLE Obtaining guidance to a particular destination, magnifying a map display, or cancelling route
guidance.
3.4
integrated system
two or more in-vehicle devices which provide information to, or receive output from, the driver of a
motor vehicle whose input and/or output have been combined or harmonized
EXAMPLE 1 An in-vehicle entertainment system and route guidance system which use the same visual and
manual input portals and visual and auditory output portals.
EXAMPLE 2 An in-vehicle entertainment system whose auditory output mutes when a mobile phone call is
made or received.
3.5
occlusion interval
time during which the driver interface is not visible when using an occlusion procedure
3.6
outlier
[6]
observation that lies outside the overall pattern of the sample data distribution
3.7
portable system
device, which provides information to, or receives output from the driver of a motor vehicle, that can be
used within the vehicle without installation or can be rapidly and easily installed in and removed from
a vehicle
2 © ISO 2017 – All rights reserved

3.8
resumability
ease with which a dialogue can be continued after it is interrupted
Note 1 to entry: A dialogue is considered resumable if task performance continues without a s
...