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JUN. 7.2004 1:01PM LEROY SIGNS NO.288 P.7i11 <br /> The various factors relating to visual perception for operation <br /> on a highway, expressed as a sigh t/d'Istance/speed relation, are shown in <br /> Figure S. The minimum and desirable minimum stopping distances are <br /> shown as they relate to the normal range of distances required for driving <br /> control. The driver recognizes elements in the visual field which serve as <br /> primary cues for the fine control task of his vehicle. Also to be considered <br /> is the "focusing distance," the point ahead upon which the driver gener- <br /> ally focuses his sight at various speeds. The driver constantly looks beyond <br /> the limits of the visual field used for fine control, concentrating toward <br /> or beyond his ability to focus. He does so to receive guidance and/or <br /> navigational information. Research and physiological studies indicate that <br /> this could be on the order of several thousand feet or even more and bears <br /> some relationship to anticipatory sight distance. <br /> As yet, anticipazory sight distance is not officially a part of <br /> the American Association of State Highway and Transportation Officials <br /> (AASHTO) design criteria, although the concept of longer sight distances <br /> under such circumstances is implied, and is being included in new criteria <br /> under preparation. Judgment based on preliminary investigations indi- <br /> cates distances on the order of three to four times the minimum stopping <br /> sight distances, and normally greater than intersection sight distances pre- <br /> vic)usly discussed, For the higher design speed highways these are in the <br /> range of 1500 to 2500 fleet. Table 10 gives anticipatory sight distances for <br /> different speeds of traffic. <br /> TA13EE 10 <br /> ANTICIPATORY SIGHT DISTANCES <br /> FOR STANDARD TRAFFIC SPEEDS <br /> Highway Design Speed (mph) <br /> 30 40 SO 60 70 80 <br /> Anticipatory sight 600 800 1100 1500 2000 3000 <br /> distance (ft.) <br /> Source; Miller, 1977 <br /> Calculating the Correct Sign Size <br /> It is possible to calculate the optimal size for a free-standing <br /> sign if the average speed of traffic on a street is known. We have developed <br /> a standard formula, based on reaction distance, which can be used to <br /> provide an initial estimate of the minimum size required for the area of <br /> a sign. <br /> 156 The S/gn User's Gulde; 4 Marketlgg A/# <br />