Railways pioneering in using less hazardous types of third rail were the New York Central Railroad on the approach to Hochbahn in Hamburg ( 1912 ) all had bottom contact rail, also known as the Wilgus-Sprague system.
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The position of contact between the train and the rail varies : some of the earliest systems used top contact, but later developments use side or bottom contact, which enabled the conductor rail to be covered, protecting track workers from accidental contact and protecting the conductor rail from snow and leaf fall.
