United States Department of Transportation
i
Usability of Light-Emitting Diodes in Precision Approach Path Indicator Systems by Individuals with Marginal Color Vision
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2014-05-01
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[PDF-1.11 MB]
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Abstract:To save energy, the FAA is planning to convert from incandescent lights to light-emitting diodes (LEDs) in
precision approach path indicator (PAPI) systems. Preliminary work on the usability of LEDs by color vision-waivered pilots (Bullough, Skinner, & Milburn, 2012) indicated that red weak (protan) individuals made a few
errors identifying red. Hence, this follow-up study explored whether clustering LEDs of different chromaticities
of the same hue would aid users with color vision deficiencies (CVD).
Participants, aged 18-33 years, included 45 with normal color vision (NCV). Additionally, 48 were diagnosed
using the Colour Assessment and Diagnosis (CAD) test as 27 deutans (including five subjects with potential
deutan deficiencies), 11 protans, two tritans, and eight subjects evidencing both red-green and yellow-blue
deficiencies. Participants completed the Dvorine pseudoisochromatic plate test, the Signal Light Gun Test (which
is the secondary test for issuing color vision waivers), the Cone Contrast Test, and a simulation of the PAPI
system. Participants were asked to name the colors of a 4-light, color-coded PAPI simulation using typical red (R)
and white (W) light configurations resulting in five possible patterns (WWWW, WWWR, WWRR, WRRR, and
RRRR) composed of either incandescent lights, or clusters of three monochromatic or three heterochromatic
5mm cylindrical LEDs.
Analyses did not indicate any significant differences between the incandescent, monochromatic, and
heterochromatic conditions. A between-group analysis found that a group comprised of those with both red-green
and yellow-blue deficiencies performed significantly worse than all other color vision groups. Performance was
not significantly different among all other groups. The protan group performed perfectly on all light sources, even
on the 16 trials without comparative color luminance cues.
This finding suggests that color vision-waivered pilots will perform the same on red and white LED PAPI
systems as with the current incandescent system.
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