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The Baltimore and Potomac Tunnel (or B&P Tunnel) is a double track, masonry arch railroad tunnel on the Northeast Corridor in Baltimore, Maryland, immediately to the south of Pennsylvania Station. Approximately 140 Amtrak and MARC passenger trains, as well as two freight trains, use the tunnel daily. The tunnel facility, which passes under the Baltimore neighborhoods of Bolton Hill, Madison Park, and Upton, consists of a series of three tunnel sections—Gilmor Street Tunnel, Wilson Street Tunnel, and John Street Tunnel—delineated by two open air cuts—Pennsylvania Avenue Opening and John Street Opening.〔〔(【引用サイトリンク】url=http://bptunnel.com/images/BP_Tunnel_Overview_V2.pdf )〕〔 ==History and operations== Constructed by the Baltimore and Potomac Railroad under Winchester Street and Wilson Street in Baltimore, the tunnel opened on June 29, 1873. The B&P tunnel allowed the Pennsylvania Railroad (PRR) direct access to Washington, D.C. for the first time by connecting its Northern Central Railway affiliate (which arrived in Baltimore from the north) to the Baltimore and Potomac's new spur, which ran to Washington. Between 1916 and 1917, the PRR lowered the floor of the tunnel approximately feet to accommodate larger trains. The work included the underpinning of the side walls, installation of a concrete invert slab, and reconstruction of the track structure. The bases of the tunnel walls were chipped away to improve horizontal clearance.〔 Prior to the electrification of the PRR's New York City to Washington main line in 1935, the poorly-ventilated tunnel easily filled with smoke from the steam locomotives then in use. The smoke also was a nuisance to the residential neighborhoods above the tunnel.〔 The tunnel was lined with gunite to waterproof the arch and prevent icicles from shorting out the catenary wires prior to the initiation of electrified operation. However, financial considerations prevented the PRR from constructing a new passenger tunnel on the Presstman Street alignment, for which it previously had acquired rights. The PRR’s plan had envisioned using the new Presstman Street tunnel and the original bores of the Union Tunnel for passenger operations, while the old B&P Tunnel and the newer bores of the Union Tunnel (completed in the 1930s) would have been used for freight operations.〔 In the late 1950s, the tunnel became a hindrance to the growth of PRR’s Trailer-on-Train service, which required additional vertical and horizontal clearance to accommodate semi-trailers on top of railroad flatcars. The curve at Pennsylvania Avenue was the biggest constraint. The PRR modified the tunnel walls and ceiling for a distance of to improve clearance and enable high cars and piggyback trailers to traverse the tunnel without damaging their roofs.〔 Additionally, a long gauntlet track was installed on southbound track 3 to route trains closer to the middle of the tunnel. However, trains could not operate on track 2 while track 3 and the gauntlet were being used. The gauntlet track effectively created a single-track tunnel when in use; if a freight train broke down while using the gauntlet, the tunnel was closed to traffic until the train was moved.〔 Even with the gauntlet, cars with a loading gauge in excess of (Plate C ) or in excess of high were prevented from using the tunnel.〔 The tunnel underwent rehabilitation as part of the Northeast Corridor Improvement Project in the early 1980s. The repairs included replacing the existing invert, repairing the tunnel lining, upgrading the track structure, installing a new gauntlet track, and rehabilitating the tunnel drainage system. No fundamental change, however, was made in the tunnel’s difficult geometry. Eventually, the gauntlet track was removed due to changes in freight traffic patterns.〔 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「Baltimore and Potomac Tunnel」の詳細全文を読む スポンサード リンク
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