Monash University Accident Research Centre - Report #206 - 2003
Authors: K. Young, M. Regan & M. Hammer
Full report in .pdf format
This report provides a comprehensive review of the current research on
driver distractions deriving from within the vehicle. The impact of
technology (e.g., mobile phones and route guidance systems) and non
technology-based distractions (e.g., eating, smoking and conversing with
passengers) on driving performance is examined and the relative influence
of these distractions on driving is discussed. Approximately one quarter
of vehicle crashes in the United States are estimated to result from the
driver being inattentive or distracted. Whilst the full extent to which
distraction is a causal factor in vehicle crashes in Australia is not yet
known, there is converging evidence that it likely to be a significant
problem here. As more wireless communication, entertainment and driver
assistance systems proliferate the vehicle market, the prevalence of
distraction-related crashes here and overseas is expected to escalate. The
various methods that have been employed to measure driver distraction are
examined and those measurement techniques that appear most promising in
being able to accurately measure in-vehicle distraction are identified. In
the final section of the report, recommendations for research and for the
management of driver distraction are provided as a first step in
stimulating development of a national agenda for dealing with this issue.
PURPOSE OF THIS REPORT
The purpose of this review, which was commissioned by Holden, is to
examine the current literature on driver distraction, focussing
specifically on in-vehicle distraction; that is, distraction caused by
activities or objects inside the vehicle rather than those outside
The first section of the report discusses the impact of
technology-based distractions (e.g., mobile phones, route navigation and
email/internet) and non-technology-based distractions (e.g., conversing
with passengers, eating/drinking and smoking) on driving performance. In
the second half of the report, the various methods that have been used to
measure distraction are described and the measurement techniques that
appear most promising in being able to accurately measure in-vehicle
distraction are identified. Future research needs and recommendations for
minimising driver distraction are made in the final section of the report.
Despite the complexities of the driving task, it is not unusual to see
drivers engaged in various other activities while driving, including
talking to passengers and listening to the radio and even reading.
Preoccupation with electronic devices while driving is also becoming
increasingly common. Any activity that distracts the driver or competes
for their attention while driving has the potential to degrade driving
performance and have serious consequences for road safety. Research by the
National Highway Traffic Safety Administration (NHTSA) estimates that
driver inattention in its various forms contributes to approximately 25
percent of police-reported crashes. Driver distraction is one form of
driver inattention and is claimed to be a contributing factor in over half
of inattention crashes (Stutts, Reinfurt, Staplin & Rodgman, 2001;
Wang, Knipling & Goodman, 1996). However, as more wireless
communication, entertainment and driver assistance systems proliferate the
vehicle market, it is probable that the rate of distraction-related
crashes will escalate (Stutts et al., 2001).
TECHNOLOGY AND NON TECHNOLOGY BASED DISTRACTION
Several in-vehicle devices and activities reviewed in this report
appear to have the potential to distract the driver and significantly
impair their driving performance and safety. The major findings to emerge
from the reviewed literature are summarised below.
- Many studies have found that using a hands-free phone while driving
is no safer than using a hand-held phone. Using a mobile phone while
driving can increase the risk of being involved in a collision by up
to four times.
- Research suggests that both the physical and cognitive distraction
caused by using mobile phones while driving can significantly impair a
driver's visual search patterns, reaction times, decision-making
processes and their ability to maintain speed, throttle control and
lateral position on the road.
- Mobile phone use also often involves associated tasks that may
further distract the driver. These activities can include writing down
phone numbers on a piece of paper whilst driving or writing down dates
or notes in diaries.
- Sending a text message is more distracting than simply talking on a
- Research has found that talking on a mobile phone is more
distracting than holding an intelligent conversation with a passenger,
but no more distracting than eating a cheeseburger.
Route Guidance Systems
- Entering destination information is believed to be the most
distracting task associated with the use of a route guidance system,
however use of voice input technology can reduce the distraction
associated with this task.
- Route guidance systems that present navigation instructions using
voice output are less distracting and more usable than those systems
that present the information on a visual display.
- Route guidance systems with voice recognition technology are a more
ergonomic and safer option than systems that require visual-manual
- Route guidance systems that provide turn-by turn instructions,
rather than presenting complex holistic route information, are less
distracting to the driver and present the most useable means of
Email and Internet Facilities
- Some researchers believe that speech-based email systems have the
potential to distract drivers and undermine road safety. As a result,
a growing number of system designers are recognising that speech-based
systems are not a panacea for driver distraction and are focusing on
developing alternative interfaces such as those that rely on tactile
- Tuning a radio while driving appears to have a detrimental effect on
driving performance, particularly for inexperienced drivers.
- Research suggests that simply listening to radio broadcasts while
driving can impair driving performance.
- Research suggests that operating a CD player while driving is more
distracting than dialling a mobile phone and eating, however the use
of voice-activation may minimise this distraction.
- A recent study revealed that a greater proportion of drivers
involved in traffic accidents are distracted by eating or drinking
(1.7%) than by talking on a mobile phone (1.5%). Another study
corroborated this finding and found that eating a cheeseburger was as
distracting as using a voice-activated dialling system, but less
distracting than continuously operating a CD player.
- Several studies have found that smoking while driving increases the
risk of being involved in a crash.
- A summary of current research on teenage passengers revealed that
the presence of passengers increases crash risk, particularly for
younger drivers, and this is believed to result largely from
distraction and peer-pressure.
In summary, there is converging evidence that both technology-based and
non-technology-based distractions can have a detrimental effect on human
driving performance. The extent, however, to which distraction compromises
safety is dependent on the frequency with which the driver is exposed to
the source of distraction in question. Very little, if anything, is
currently known in Australia (and indeed in most other countries) about
the relative frequency with which technology and non-technology-based
tasks are performed. The findings reported here do, nevertheless, provide
important information that can be used to optimise the ergonomic design of
the Human Machine Interface (HMI) in vehicle cockpits and inform the
development of other countermeasures for minimising driver distraction.
RECOMMENDED DISTRACTION MEASUREMENT TECHNIQUES AND MEASURES
In addition to reviewing what is known about both technology and
non-technology-based distractions deriving from within the vehicle, the
authors reviewed the various scientific techniques which have been used to
measure driver distraction and the measures of driving performance (e.g.,
lane keeping) which appear to be vulnerable to the different types of
distraction. While this material was reviewed primarily to assist Holden,
it is reported here to assist others undertaking distraction-related
research. The following scientific techniques for measuring distraction
- on-road and test track studies;
- driving simulator studies;
- dual-task studies;
- eye glance monitoring studies;
- the visual occlusion method;
- the peripheral detection task; and
- the 15 Second Rule.
The findings of this review suggest that using a range of distraction
measurement techniques, rather than a single technique, would be
appropriate in evaluating HMI design concepts and prototypes in vehicles.
The particular technique, or sub-set of techniques, employed, however,
will depend on the particular aspect of the HMI to be assessed, and in
particular on the form of distraction (e.g., visual, physical etc) that is
imposed on the driver by that aspect of the interface. With the possible
exception of on-road and test track studies, and the 15-second rule, all
of the above methods are considered suitable for use in HMI evaluation
studies. On-road studies are more dangerous to conduct and are less
experimentally controlled than simulator studies, and there is some doubt
in the literature about the validity of the 15-second rule.
COUNTERMEASURES FOR MINIMISING DISTRACTION
Whilst the magnitude of distraction as a road safety problem in
Australia is not yet fully known, there is converging evidence from
studies overseas that it is likely to be a significant issue here and that
it is likely to become a greater contributor to road trauma as the number
of technology-based sources of distraction in vehicles increases. On the
basis of the literature reviewed, the following recommendations are made
for minimising the effects of driver distraction.
- A carefully designed study of the prevalence of driver involvement
in distracting activities within the vehicle should be undertaken.
This information, combined with the epidemiological data from the
previously mentioned study being conducted by the University of
Western Australia Department of Public health Injury Research Centre,
will enable an initial assessment of the magnitude of the problem in
Australia to be made. If driver distraction is shown to be a
significant problem, then better recording by Police of the role of
distraction in crashes will be needed.
- An inventory of existing and emerging technologies and services
which can be accessed on-board the vehicle or through portable devices
carried into the vehicle should be compiled. From this, research is
needed to develop a taxonomy of driver distractions that defines the
different sources of distraction deriving from within the vehicle and
categorises them according to how distracting they are in absolute and
- Research is required to better understand drivers' willingness to
engage in potentially distracting tasks while driving, the factors
that influence this willingness and under what conditions drivers
engage in distracting tasks.
- There is currently little knowledge regarding how drivers use
in-vehicle technologies: whether they use them in the manner intended
by the designer; and at what point (or threshold) and under what
conditions they become a distraction.
- Research needs to be conducted into whether and how individual
difference factors such as age, gender, driving skill and experience
influences the ease with which drivers are distracted.
- To complement the above activities, research is needed to develop a
taxonomy of distracting events and objects occurring outside the
vehicle. As for sources of distraction deriving from within the
vehicle, research is needed to quantify how distracting they are in
absolute and relative terms, alone and in combination with internal
distracters. Some research on this issue is being undertaken by the
Monash University Accident Research Centre and this should be closely
- There is a need to develop objective, standardised, measures of
distraction in order to enable more accurate comparisons of results
across studies (NHTSA, 2002a).
- Further research is needed on alternative modes of input and output,
such as tactile feedback and voice activation, to determine whether
these interaction methods are a safe and viable alternative to manual
- The operation of certain on-board and portable technologies, such as
mobile phones, often involves associated tasks such as writing down
phone numbers and address details on pieces of paper. There is a need
for research to design the HMI so that it eliminates as far as
possible the need for these secondary tasks.
- No research, to the knowledge of the authors, has examined the
potentially distracting effects of portable devices used by
pedestrians and other road users (e.g., mobile telephones, pedestrian
navigators) to access information and services when negotiating their
way by means other than driving through the road system.
- The overall costs and benefits afforded by various technologies must
be assessed before restricting or prohibiting drivers from engaging in
distracting tasks while driving. Listening to a radio broadcast, for
example, might be distracting: yet, for a truck driver, this activity
might be beneficial in maintaining vigilance in a low workload driving
Education and Training
- A good deal is already known about the risks associated with
engaging whilst driving in various distracting activities. It is
important that these are brought to the attention of drivers and
passengers. As a matter of priority, it is important to make the
motoring public aware that hands-free mobile phones can be just as
distracting as hand-held phones.
- As with the use of mobile phones, drivers must be educated and
trained in the optimal manner in which to interact with existing and
emerging on-board technologies and services accessed through portable
devices in order to minimise distraction.
- Where flexibility exists in the manner in which these devices can be
operated (there are, for example, many ways to tune and select a radio
station), user manuals and tutorials provided by vehicle manufacturers
and service providers should highlight the most ergonomic and least
distracting methods for doing so.
Legislation and Enforcement
- Existing legislation should be reviewed and, where necessary, new
legislation created to limit driver exposure to, and deter drivers
from engaging in, activities which have the potential to distract
them. There is sufficient evidence, for example, to justify a ban on
the use of hands-free phones whilst driving if this can be practically
enforced by the Police.
- The most effective way to minimise technology-based distraction is
to design the Human Machine Interface (HMI) ergonomically. In Europe,
North America and Japan, draft standards have already been developed
which contain performance based goals which must be reached by the HMI
so that the in-car technologies do not distract or visually entertain
the driver while driving (e.g., the European Statement of Principles
for Driver Interactions with Advanced In-vehicle Information and
Communication systems). It is important that the development of these
standards be closely monitored by relevant authorities in Australia
and that local vehicle manufacturers and system developers are
encouraged to refer to these standards in designing their
- The operation of certain devices including mobile phones and route
guidance systems often involves associated tasks such as accessing
written information, which can further distract the driver. There is a
need for research to develop the HMI so that it eliminates the need
for these associated tasks.
- Handbooks for learner and probationary drivers should draw attention
to the potential risks associated with engaging in distracting
activities within the vehicle.
- Knowledge tests should include items pertaining to the relative
risks associated with engaging in these activities.
- Where appropriate, the graduated licensing system should be used to
restrict driver exposure to distracting activities that are known to
compromise safety. The findings presented here, for example, suggest
that there is a case for restricting Probationary drivers from using
(but not carrying) mobile phones while driving during some or all of
Fortunately, we are at an early enough stage in the evolution of the
vehicle cockpit to prevent distraction from escalating into a major road
Sponsoring organisation: Holden Ltd.