DETECTION AND IDENTIFICATION OF LIGHT-EMITTING DIODE TRAFFIC SIGNALS BY PROTAN OBSERVERS

Document Type

Journal Article

Publication Date

2003

Subject Area

operations - traffic, infrastructure - traffic signals, policy - disability

Keywords

Yellow, Wavelength, Visually impaired persons, Traffic signals, Traffic lights, Traffic control signals, Red, Reaction time, People with visual disabilities, Light emitting diodes, LEDs, Incandescent lamps, Highway traffic signals, Detection and identification, Daylight

Abstract

Protan observers have lower spectral sensitivity than color-normal observers at long wavelengths of the visible spectrum. Responses of protan and color-normal subjects to light emitting diode (LED) and incandescent traffic signals of red and yellow nominal color during simulated daytime viewing conditions are described. Reaction times, missed signal percentages, and color-identification accuracy were measured. The results indicate that for protans, detection performance to red LED signals was enhanced when the dominant wavelength was moved toward shorter wavelengths, but this shift also appeared to decrease their ability to correctly identify the signal color. Although the yellow LED signal used in this study provided similar detection performance for protans as a yellow incandescent signal, its dominant wavelength was sufficiently long for it to sometimes be confused with red. In general, the results of this study are consistent with the 1994 recommendations of the Commission Internationale de l'Eclairage for signal colors to be seen by color-normal and protan observers. Nonetheless, neither detection nor color identification for protans approached that of color-normal observers.

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