Geography Reference
In-Depth Information
This paper reports on the outcomes of the considerations of the usability of the
Web-delivered maps for colour-blind users.
Considering the Colour-Blind
Humans perceive colour using photosensitive cones. The grey component of
colours is perceived through the bleaching of photosensitive rods. Users lacking
certain colour-receptive cones or who have damaged cones will not be able to see
some of the red, green and blue components of the visible colour spectrum. 0.01 %
of all Caucasian females and 2 % of all Caucasian males have deuteranopia/
deuteranomaly, where the retina lacks red-sensitive cones (Light and Bartlein
2004
). The more common forms of colour impaired vision are deuteranopia/deu-
teranomaly/Dalonism (green-weakness) (0.25 % of Caucasian females and 6 % of
Caucasian males). These users are less sensitive to medium wavelengths—greens.
They have a decreased ability to discriminate the green component of colours
(Stephenson
2005
). Protanopia is red-blind. Tritanopia is the rarest form of
colour-blindness and is the lack of functional cones altogether.
The greatest confusion area is red-green confusion. Of the three colour-blindness
examples illustrated, only Tritanopiates would be able to discriminate between the
different zones of grasslands. Tritanopia is the rarest form of colour-blindness.
Therefore colour design strategies are needed to ensure that different colours can be
discriminated.
Design Strategies
One simple strategy is to ensure that all information conveyed with colour is also
available as one colour tone. With paper mapping a number of innovative works
have been undertaken to produce products that work for all users, irrespective of
colour deficiencies. This has usually been achieved by producing a monochrome
map. One example is the
for Manhattan. The current
New York Subway map, designed by Michael Hertz, was introduced in 1979
(Hogarty
2007
). It replaced the earlier (lauded) version that had been designed in
the 1970s by acclaimed graphic designer Massimo Vignelli (Rawsthorn
2012
).
A prototype Subway map for the colour-blind was produced by Brooklyn based
designers Triboro Design (
www.triborodesign.com/
)
. It was produced in just one
colour: florescent red. The 45
Color Blind Subway Map
'
'
58 in. poster is the same size as the MTA Subway
maps that are placed on the walls at New York Subway stations. This map is shown
in Fig.
1
.
Jenny and Kelso (
2007
) suggested some basic methods to ensure that colour-
blind users are able to distinguish between different mapped elements, viz:
