Abstract
The purpose of this investigation was to evaluate the relationship between highway sign brightness and alcohol impairment under night driving conditions. Sign brightness was controlled by varying sign reflectivity and headlight brightness. Data were collected under controlled conditions with the subjects actually driving the vehicle. The dependent measure was the correct reading distance. Three blood alcohol concentrations (BAC's) were investigated: sober, 0.08%, and 0.15%. Fourteen subjects participated under a different BAC on each of three separate nights.
Results confirmed the experimental hypotheses that high reflectance signs significantly increase sign–reading distance under night driving conditions and that alcohol-impaired drivers require significantly brighter signs. Increases in both sign reflectance and headlight brightness yielded significant improvements in sign–reading performance under all three BAC conditions. A significant interaction between the reflectance and headlight main effects indicated that the higher reflectance signs yielded a greater relative improvement in sign–reading performance under low–headlight conditions than under high–headlight conditions.
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