On-the-Move and in Your Car - Human-Computer Interaction and Innovation in Handheld, Mobile and Wearable Technologies - page 63

THE HUMAN-CENTRED
DESIGN PROCESS

(Green, 2003). Moreover, studies have shown a
limited ability to divide attention and prioritise
sources of information, largely due to lack of
driving experience (Wickman, Nieminem and
Summala, 1998). Subsequently, system block
outs, which prevent the use of complex functions
in inappropriate driving situations, are likely to be
of particular benefit for these individuals.
In contrast, older drivers often suffer from a
range of visual impairments which can lead to a
range of problems with in-vehicle displays. For
instance, presbyopia (loss of elasticity in the lens
of the eye) is extremely common amongst older
people, as is reduced contrast sensitivity. Studies
consistently show that older drivers can take 1.5
to 2 times longer to read information from an
in-vehicle display compared to younger drivers
(Green, 2003). Given that drivers have a limited
ability to change the distance between themselves
and an in-vehicle display, the size, luminance and
contrast of presented information are obviously
critical design factors.

The fundamental components of a human-focused
approach hold true for in-car computing, as much
as for any interactive product or system, that is,
early focus on users and tasks, empirical mea-
surement and iterative design (Gould and Lewis,
1985). A comprehensive understanding of the
context in which in-car computing devices will
be used is especially important early in the design
process. Context of use refers to “the users, tasks
and equipment (hardware, software and materi-
als), and the physical and social environments in
which a product is used” (Maguire, 2001, p.457).
A context of use analysis assists in developing the
initial requirements for a design and also provides
an early basis for testing scenarios. Moreover,
context of use analysis provides a focused ap-
proach which helps to ensure a shared view among
a design team. In the driving situation, there are
several context of use issues which will have a
significant effect on how an in-car computing
system is subsequently designed. Accounting for
these raises many unique challenges for in-car
user-interface designers.

Tasks

A key task-related issue is that the use of an in-car
computing system is likely to be discretionary.
Drivers do not necessarily have to use the sys-
tem to achieve their goals and alternatives will
be available (e.g. a paper map, using the brake
themselves). As a result, the perceived utility of
the device is critical. Furthermore, drivers' affec-
tive requirements may be particularly important.
In certain cases, this requirement may conflict
with safety-related needs, for instance, for a
simple, rather than flashy or overly engaging
user-interface.
The factor that most differentiates the driving
context from traditional user-interface design is
the multiple-task nature of system use, and in this
respect, there are two critical issues that designers
must take into consideration. The first concerns
the relationship between primary driving tasks and
secondary system tasks, as drivers seek to divide

Users

As with many other consumer products, there will
be a large variability in user characteristics (e.g.
in perceptual/cognitive abilities, computer experi-
ence, anthropometry) to consider when designing
in-car computing systems. Car manufacturers may
have particular socio-economic groups in mind
when designing a vehicle, but the user base may
still be extremely large.
One fundamental individual difference factor
often addressed in research is driver age - drivers
can be as young as 16 (in certain countries) and
as old as 90. In this respect, younger drivers may
be particularly skilled in the use of computing
technology, in comparison with the population
at large, but are especially prone to risk taking