Abstract
Two independent studies, each employing 12 subjects sitting in a stationary car on an unused airport runway with low beams on, were conducted to determine the distance at which a shape coded, reflectorized warning plate can be recognized at night as a function of target brightness. Recognition distances were recorded for a balanced combination of 15 experimental conditions consisting of 3 different specific intensity levels of target brightness (high 1080 cd/fc/sq ft at .2 degrees observation angle and −4 degrees entrance angle; medium 305 cd/fc/sq ft and low 105 cd/fc/sq ft) and 5 different shapes of equal area (18 square inches) targets (rectangle, circle, square, triangle, octagon). Study 1 used a car heading angle of 10 degrees to the right while Study 2 used a car heading angle of −3 degrees to the left. Results of these studies indicated that increasing target brightness had either no effect or only a small effect on target recognition distance, and the triangle (the object with the longest sides) was recognized at the largest distance and with the fewest errors. Targets were also recognized further away at the 10 degree car heading angle (less beam illumination) than at the −3 degree car heading angle (near maximum beam illumination). Implications of these results for the design and display of shape coded reflectorized warning plates in both traffic and industrial settings are discussed.
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