甲武鉄道国有化・複々線化と飯田橋駅 The Nationalization of Kobu Railways and Construction of Multiple Lines and Iida Station 1906（明治39）年に甲武鉄道は国有化され、1909（明治42）年に中央東線（1911（明治44）年に中央本線に改称）の一部となりました。 甲武鉄道の乗客数は、開業した1894（明治27）年には85万８千人、翌年には242万２千人と急増していました。大幅に増えた旅客輸送に対応するため、汽車・貨物と電車の分離を目的に、1922（大正11）年から複々線化工事が行われました。複々線化の際、牛込駅下りホーム等が支障となったため、1928（昭和３）年に電車線の飯田町駅（現在の千代田区飯田橋三丁目）と統合する形で、そのちょうど中間となる曲線位置に飯田橋駅が開業しました。 開業当時の飯田橋駅は両端に出口があり、東口側は高架駅のような構造になっている一方、西口側は橋上の駅舎でした。この西口は旧牛込駅の利用者に対して影響が少なくなるよう設けられたものであり、長い通路が造られ、2016（平成28）年まで使用されていました。駅の屋根は古レールを使って作られ、現在もホーム上から確認することができます。 飯田橋駅のホームは急曲線にあったため、車両の大型化に伴いホームと電車の間には広い隙間ができていました。2020（令和２）年に、ホームを牛込駅があった市ヶ谷駅寄りの直線部分に移設し、より安全な直線ホームに改められました。あわせて、地域のシンボルとして史跡を活かした駅前広場や駅舎が整備されました。
JR 東日本中央本線【飯田橋駅】ホーム上屋古レール全景
冒頭でも触れた西口への通路も古レールが下部構造に大量に使用されている。まるで線路上から撮影したような写真であるが、あくまでもホーム上から撮影したものであり、ホームの曲がり具合が相当のものであることを実感できる。奥に見える下駄ばきの建物が西口の駅舎である。
JR 東日本中央本線【飯田橋駅】西口通路古レール全景
同通路を西口改札外の牛込橋付近より見下ろす。これだけの長さで立ち上がる古レールが延々と続くのは壮観である。しかし、現在の耐震基準ではまずアウトではなかろうかと思われる華奢な架構とも言える。一体どのような構造計算の結果で OK となったのだろうか。
JR 東日本中央本線【飯田橋駅】西口通路古レール全景
Kōbu Railway was nationalized in 1906 and became part of the Chūōtō Line in 1909. Two years later, the Chūōtō Line’s official name was changed to the Chūō Main Line. In 1894, Köbu Railway’s ridership numbered 858,000. By the following year, it had nearly tripled to 2,422,000. In 1922, additional lines were constructed in order to accommodate the line’s rapidly expanding ridership and to separate the steam and freight lines from the electric passenger lines. In 1928, Ushigome Station was merged with Iidamachi Station (present-day Chiyoda Ward Iidabashi 3-chome) because the platform for its outbound line obstructed the construction of the additional lines. This led to the creation of Iidabashi Station, which was located along a curve section of track equidistant from Ushigome and Iidamachi Stations. At the time of its opening, there were entrances at both ends of Iidabashi Station. While the eastern side had an elevated, viaduct-like structure, the eastern portion was located on a bridge. In order to accommodate passengers who previously boarded the train at Ushigome Station, a long passage connecting Iidabashi Station with its western entrance was constructed and remained in use until 2016. The Station’s roof was constructed using old pieces of rail track. These sections of the roof are visible today from the station platform. Because Iidabashi Station was located along a sharp curve, the construction of larger rail cars resulted in a wide gap between the platform and trains that served the station. In 2020, the platform was relocated to the straight section in the direction of Ichigaya Station previously occupied by Ushigome Station. This narrowed the gap between the platform and trains and made it safer for passengers to board. In conjunction with the platform’s relocation, a station-front plaza and station XX, was constructed.
Ushigome Station opened on October 9, 1894, the same day that Kōbu Railway initiated service between Shinjuku and Ushigome Stations. Before Iidama-chi Station opened on April 3, 1895, Ushigome Station served as the starting station on the Kōbu Line. Ushigome Station was located on the portion of present-day Iidbashi Station that extends from Ushigome Bridge in the direction of Ichigaya Station. At the time, portions of the outer moat were reclaimed in order to construct the station house and train tracks. Ushigome Station’s platform was located on the site currently occupied the JR Chuo Rapid Transit Line. In addition, the station house was constructed on the site currently occupied by the JR Chuo and Sobu Local Lines. Ushigome Station had two ticket gates. One was located on the present-day Shinjuku Ward side and the other was located on the Chiyoda Ward side. The gate building on the Chiyoda Ward side was constructed facing the road alongside the outer moat’s embankment and could be accessed by a staircase that rose from the Station’s rail bridge and climbed the embankment. A retaining wall from a section of the embankment next to the station house remains in place today in the vicinity of the entrance to Sotobori Park. On the Shinjuku Ward side, a road was constructed on land reclaimed from alongside Ushigome-mon Gate’s earthen bridge. Thereafter, Ushigome Station could be reached via a small pedestrian bridge, which was erected near the aqueduct attached to Ushigome-mon Gate’s weir. Today, portions of the foundation that supported the pedestrian bridge remain in place and are visible from Iidabashi Station’s platform and atop Ushigome Bridge.
