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Horseshoe Curve is a three-track railroad curve on the Norfolk Southern Railway's Pittsburgh Line in Blair County, Pennsylvania. The curve itself is about long and in diameter; it was completed in 1854 by the Pennsylvania Railroad as a way to lessen the grade to the summit of the Allegheny Mountains. It eventually replaced the time-consuming Allegheny Portage Railroad, the only other route across the mountains for large vehicles. The rail line has been important since its opening, and during World War II the Curve was targeted by Nazi Germany in 1942 as part of Operation Pastorius. The Curve was later owned and used by Pennsylvania Railroad successors Penn Central, Conrail, and Norfolk Southern. Horseshoe Curve was added to the National Register of Historic Places and designated a National Historic Landmark in 1966, and became a National Historic Civil Engineering Landmark in 2004. Horseshoe Curve has long been a tourist attraction with a trackside observation park being completed in 1879. In the early 1990s the park was renovated and a visitor center built; the Railroaders Memorial Museum in Altoona manages the center, which has exhibits pertaining to the curve. == Location and design == Horseshoe Curve is on the Pittsburgh Line, the Norfolk Southern Railway Pittsburgh Division main line between Pittsburgh and Harrisburg, Pennsylvania. Westbound trains climb a maximum grade of 1.85 percent for from Altoona to Gallitzin; just west of the Gallitzin Tunnels trains pass the summit of the Allegheny Mountains, then descend for to Johnstown on a grade of 1.1 percent or less. The curve is west of Altoona in Logan Township, Blair County at railroad milepost 242. The Blair County Veterans Memorial Highway (SR 4008) follows the valley west from Altoona and tunnels under the curve.〔(Act of Dec. 4, 1992, P.L. 775, No. 120. )〕 Horseshoe Curve bends around a dam and lake, the highest of three reservoirs along the valley which are owned by the Altoona Water Authority and supply water to the city. Horseshoe Curve spans two ravines formed by creeks: Kittanning Run on the north side of the valley, and Glenwhite Run on the south. For every , the tracks at the Horseshoe Curve bend 9 degrees and 15 minutes with the entire curve totaling 220 degrees. The curve is long and, at its widest, about across. The Horseshoe Curve descends from an approximate elevation of on the southern side to on the northern. The grade of the curve was listed by the Pennsylvania Railroad as 1.45 percent, and currently as 1.34 percent by Norfolk Southern.〔〔 Each track consists of , welded rails that were, , laid in 2011. Prior to dieselization and the introduction of dynamic braking and rail oilers, the rails along the curve would be transposed—left to right and vice versa—to equalize the wear on each rail from the flanges of passing steam locomotives and rail cars, thereby extending their lifespan. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Horseshoe Curve (Pennsylvania)」の詳細全文を読む スポンサード リンク
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