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The Portal Bridge is a railroad bridge over the Hackensack River in northeastern New Jersey, USA, just west of Secaucus Junction. It is a two-track, moveable swing-span between the towns of Kearny and Secaucus owned and operated by Amtrak as part of the Northeast Corridor and also used by New Jersey Transit. , it is considered the busiest train span in the Western Hemisphere,〔 carrying between 150,000 and 200,000 passengers per day.〔〔〔 Originally opened in 1910,〔 the bridge was built by Pennsylvania Railroad in conjunction with service to the newly constructed Pennsylvania Station in New York City. The bridge is considered obsolete and under review for replacement. Currently, the bridge limits train speeds to 60 mph〔〔〔 and is so low that it often has to be opened to allow commercial boats to pass underneath it causing more delays.〔〔 For these reasons, it has been called the Achilles' heel of the Northeast Corridor.〔 Existing design and engineering plans for the bridge's replacement call for two fixed bridges. Work on the replacement bridges has stalled due to lack of funding and as of 2014 funding for the $940 million to build it had not been identified.〔 ==Design and construction== Portal Bridge is a steel structure with masonry abutments. The bridge consists of a through-truss swing span and six (three on each side of the center span) 110-foot-long open-deck girder approach spans.〔 The bridge itself is partially made of wood.〔 The bridge's lowest beams are just above the surface of the Hackensack River at high tide.〔 When closed to river traffic, the bridge bears upon six wedge blocks. Two blocks are at each end of the bridge while two more sit adjacent to the center of the bridge. After the wedges are withdrawn the center-bearing supports the structure as the bridge is opened and returns it to its closed position once the river traffic has passed through one or both of the navigation channels. Construction of the bridge was begun in August 1905, and the bridge was placed in service on November 27, 1910,〔 based on bridge designs from the 1840s.〔 The bridge was designed to last 100 years.〔 Overhead catenary to supply power to electric locomotives was installed in the 1930s.〔 Some of the bridge machinery was updated in 1931. Minor repairs were made in the 1970s, and major repairs to structural mechanical and electrical equipment were completed as part of Amtrak's Northeast Corridor Improvement Project between 1982 and 1984 by William F. Hegarty, Inc. of East Hanover, NJ. 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「Portal Bridge」の詳細全文を読む スポンサード リンク
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