Wig-wag (automobile)
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A wig-wag is a device for flashing an automobile's headlights at a preset rate. Traditionally, the wig-wag will flash the right and left headlights (often the high-beams) alternately, but some designs will flash both headlights on and off together. More complex wig-wags may cycle through several patterns, such as swiftly alternating the left and right headlights, alternating the left and right headlights slowly, flashing both headlights together, and then repeating the cycle. Although the use of flashing headlights does increase the visibility of any vehicle operating them, it can also create problems. Particularly when highbeam headlights are flashed, the wig-wag may create glare or may otherwise temporarliy blind the drivers of oncoming vehicles. Wig-wags may also cause "moth effect," in which other drivers are attracted to the flashing lights, ultimately causing them to ram the vehicle in which those lights are installed; this continues to be debated. (see [1]) (PDF file)
Generally, wig-wags are prohibited on all vehicles except emergency vehicles, however the road rules in New South Wales, Australia, allow school buses to have flashing headlights [2] (PDF file).
