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Wigwag (railroad)
Wigwag is the nickname given to a type of railroad grade crossing signal once common in North America, named for the pendulum-like motion it used to signal the approach of a train. It is generally credited to Albert Hunt, a mechanical engineer at Southern California's Pacific Electric (PE) interurban streetcar railroad, who invented it in 1909 for safer railroad grade crossings. The term should not be confused with its usage in Britain, where wigwag is generally used to refer to alternate flashing lights, such as those found at modern level crossings.〔(Traffic Light System ) Auto Mate Systems〕
==Rationale==
Soon after the advent of the automobile, speeds were increasing and the popularity of enclosed cars made the concept of "stop, look, and listen" at railroad crossings difficult. Fatalities at crossings were increasing. Though the idea of automatic grade crossing protection was not new, no one had invented a fail-safe, universally recognized system. In those days, many crossings were protected by a watchman who warned of an oncoming train by swinging a red lantern in a side-to-side arc, used universally in the U.S. to signify "stop". This motion is still used today by railroad workers to indicate stop per the General Code of Operating Rules (GCOR) Rule 5.3.1. It was presumed that a mechanical device that mimicked that movement would catch the eye of approaching motorists and give an unmistakable warning.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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