A funicular railroad can use two, three or four rails. In a common three-rail configuration (Dubuque, Iowa) the center rail is common for both cars with a passing area in the middle of the run. In a two-rail configuration, a similar passing area in the center of the run allows the cars to pass one another. In a four-rail configuration (Johnstown, Pennsylvania) no passing area is required.
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A tug, usually electric and usually located at the top of the incline, pulls the ascending car while controlling the gravitational pull of the descending car, all connected on one cable. (There is usually a backup cable.)
At one time, funicular railroads were quite common in the United States and around the world. Although there aren't so many now, in several places, a funicular railway remains the best way to get to the top of the hill.