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Auuendix C — Electronic Outdoor Advertisine Device Visual Performance Definitions <br />Conspicuity <br />Conspicuity is the property that related to the contrast between a sign and its background and <br />its ability to stand out from its surroundings. This is a subjective property that depends on <br />many factors of both the environment and the viewer. <br />Contrast <br />Contrast is the property that defines the relationship between the brightness of the brightest <br />color possible to the darkest color possible on a sign. In times when ambient conditions are <br />very bright, such as a sunny day, the darkest color may still be very bright due to the sun's <br />reflection off the sign. In these cases, the lighter colored areas of the billboard's image must <br />be much brighter than the contrasting dark areas. <br />Legibility <br />The ability of the driver to read a sign is related to its legibility. Large, legible text allows <br />the driver to read the billboard from varying distances and focus on the driving task. <br />Conversely, with small text the driver is more likely to focus on the sign for a longer period <br />of time and possibly wait until the sign is very close. <br />State depaitlnents of transportation use NEMA's TS-4 document for this criterion. This <br />document specifies many characteristics related to legibility including character height, <br />resolution and color. <br />Glare <br />Disability Glare <br />The first form of glare is disability glare. This occurs when a driver is exposed to a light <br />source so bright that it temporarily blinds the driver, impairing their ability to perform <br />driving tasks. This temporary blindness is brief, but can be dangerous. <br />Discomfort Glare <br />Discomfort glare is when a light source is bright enough to distract or encourage the driver to <br />look away from the light, but is not blinding. Discomfort glare is of particular concern in <br />cases where a bright sign is located in the same line of sight as a traffic sign, signal or <br />another vehicle. <br />Frequency of Change <br />The frequency of change is determined by the interval of time between sign image changes. <br />The rate of change can usually be adjusted by the owner and operator of the sign. Frequency <br />c-1 <br />