Abstract
A study, using 11 subjects sitting in a stationary car on an unused airport runway with low beams on, was conducted to determine the distance at which a shape coded, white, reflectorized warning plate can be recognized at night as a function of the amount of reflectorization (either fully reflectorized or borders only reflectorized) and as a function of target brightness. Recognition distances were recorded for a balanced and randomized combination of 30 experimental conditions consisting of 3 different specific intensity levels of target brightness (high, prismatic sheeting material, 1080 cd/fc/sg ft at .2 degree observation angle and −4 degrees entrance angle; medium, encapsulated lens, 305 cd/fc/sq ft; and low, embedded or enclosed lens, 105 cd/fc/sq ft), 5 different target shapes of equal area (18 square inches, rectangle, square, triangle, circle and octagon), and two different types of reflectorization (targets that were fully reflectorized and targets that had only 4.25 square inches along their borders reflectorized). A car heading of −3 degrees to the left was used for the experiment to maximize target illumination. The results indicate that increasing target brightness had either no effect or only a small detrimental effect on correct target recognition distances for both the full reflectorization and borders only reflectorization, and that the triangle (the object with the fewest and longest sides) was recognized at the largest distance and with the fewest errors for both the full reflectorization and borders only reflectorization. The embedded or enclosed lens sheeting material transmitted the most information and produced the highest percentage of correct responses. Targets with the borders only reflectorized were also recognized further away than the fully reflectorized targets (15% futher for 23.6% reflectorization). Implications of these results for the design of shape coded reflectorized warning plates for night use for both traffic and industrial settings are discussed.
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