Cause And Effect Of Fog Essay

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contribute to road collisions by decreasing visibility distance and target detectability, especially in older drivers (Ni, Bian, Guindon & Andersen, 2012) and others with reduced contrast sensitivity. In addition, fog has more subtle perceptual effects that are equally important. These include misjudgments of speed and distance and the narrowing of visual attention. During the day, fog operates much like the atmospheric effects described above, lowering contrast through extinction and scatter. In this case, however, the particles are a suspension of very fine water droplets in the air. Extinction and contrast loss depend on the distance of the object and on size and density of the moisture droplets suspended in the atmosphere. Since the droplets are bigger than wavelengths in the visible spectrum, there is no color selectivity. This is why yellow fog lights do not provide improved visibility over white lights. Lastly, visibility may also be a function of sun altitude and viewer orientation with respect to the sun. At night, light beams, such as car headlamps, complicate fog effects. There are extinction and air light effects in both directions—when the light goes from source to object and then when it is reflected back to the eye. Fog weakens the headlamp’s effectiveness by scattering the light …show more content…

Moving objects appear slower. First, fog lowers the apparent speed of other objects in the visual field by reducing contrast. Low contrast objects appear to move slower (e.g., Anstis, 2003; Green, 1993; Snowden, Stimpson, and Ruddle, 1998; Stone and Thompson, 1992), so discrimination between moving and stationary objects is more difficult. Imagine a person driving along a freeway and seeing a faint car. It will be very difficult to detect that it has stopped because the lower contrast impairs speed judgments. Moreover, the driver has an expectation that cars do not stop on freeways. The driver may then fail to realize that the car ahead is stopped until it is too

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