Improvement of Shimbashi Station on the Ginza Subway Line (the first subway in the East) Atsushi NUMATA1, Yasushi ARAI2 1Design Section Chief of the Renovation & Construction Department of Railway Headquarters, Tokyo Metro Co.,Ltd, 3-19-6, Higashi-ueno, Taito-ku, Tokyo, Japan, [email protected] 2 Design Section Deputy Manager of the Renovation & Construction Department of Railway Headquarters, Tokyo Metro Co.,Ltd, 3-19-6, Higashi-ueno, Taito-ku, Tokyo, Japan, [email protected] ABSTRACT: The Tokyo Metro railway network opened in December 1927 as the first subway in the east, with a 2.2-km stretch between Asakusa and Ueno on what is now the Ginza Line(Figure 1).By the time the Fukutoshin Line opened in June 2008, the network had expanded to include nine lines over a 195.1 km span of open tracks. Shimbashi Station is located at about the middle of the Ginza Line. It is a transfer station for JR, Toei subway lines, and the AGT system (the Yurikamome). Increases in the number of passengers in recent years have caused major obstructions to passenger flow. In addition, the structure of Shimbashi Station is integrated with the piers of the JR Bridge, and is adjacent to the piers of the Tokaido Shinkansen Bridge. Based on passenger flow simulations under the configurations of the existing station, this plan proposed sweeping changes to the layout of the station to alleviate congestion on the platforms and facilitate smooth transfers to other modes of transportation. INTRODUCTION The Tokyo Metro Ginza Line (“Ginza Line”) became the first subway in the eastern hemisphere when the 2.2-km stretch between Asakusa and Ueno stations opened on December 30, 1927. The open-cut method was used to construct most of the Ginza Line, the majority of which runs less than 10 meters below the ground surface. The Ginza Line is one of Tokyo’s main train lines and now runs from Asakusa Station in Taito City to Shibuya Station in Shibuya City over a total distance of 14.3 kilometers. The 89-year-old line still enjoys high ridership because it connects to Omotesando, Ginza, Ueno and other of Tokyo’s main districts, thus trains leave every two minutes during rush hour, and every three minutes during mid-day. The Ginza Line Shimbashi Station (“Shimbashi Station”) is a critical metropolitan transportation hub that serves over 220,000 passengers each day and provides connections to Japan Railway (JR), Tokyo Metropolitan Bureau of Transportation (Toei subway) and Yurikamome Lines. This report explains the problems with the current condition of Shimbashi Station as well as major improvement work aiming to solve those problems. SHIMBASHI STATION: A JSCE CIVIL ENGINEERING HERITAGE History The Ginza Line between Asakusa and Shimbashi Stations marked the first time steel- framed structures, the precursors to steel-reinforced concrete structures, were used in Japan, and the many arches used in station buildings, the tunnel that runs along the bottom of the Kanda River between Suehirocho and Kanda Stations, and other treasured structures are being used to this day. In recognition, the Japan Society of Civil Engineers recognized this section of the Ginza Line as a Civil Engineering Heritage on August 29, 2008(Figure 2). Shimbashi Station stands out further from these celebrated structures because of its special historical background, explained below. Tokyo Metro currently operates all 14.3 kilometers of the Ginza Line, but originally Tokyo Metro operated the 8.0-kilometer stretch between Asakusa and Shimbashi Stations while Tokyo Rapid Transit Railway operated the 6.3-kilometer stretch between Shimbashi and Shibuya Stations. The two companies began construction to allow the line to run directly through Shimbashi Station, and Tokyo Rapid Transit Railway finished its side of Shimbashi Station first, on January 15, 1939. Tokyo Metro built a station (the current Shimbashi Station) on the Asakusa side of the existing Shimbashi Station and opened it when the completed Ginza Line from Asakusa to Shibuya was opened on September 16, 1939. The platform on the Tokyo Rapid Transit Railway side that was used for that eight-month period was retired from use but never demolished, and is now used to store two six-car trains (Picture 1). It is known familiarly as “The Phantom Platform of Shimbashi Station.” Current structure Figures 3 and 4 show floor plans for the current Ginza Line Shimbashi Station B1 floor concourse and B2 floor platforms, respectively. Figure 5 is a three- dimensional diagram of the station, and Table 1 shows the station structure specifications.The station originally featured an island platform, but passenger traffic during the morning and evening rushes grew with the soaring Japanese economy. In 1980, the island platform was converted for Shibuya-bound trains only, while a new platform exclusively for Asakusa-bound trains was built by expanding outside the existing frame of the station structure, creating the irregular divided platform structure still in use today. To make the station a universally accessible facility, one elevator to the B1 floor concourse was installed on each B2 floor platform, and one elevator from the B1 floor concourse to the ground level was also installed. Table 1 Shimbashi Station Structure Specifications (Current) Platform Length Station Platform Platform Structure Platform for for Depth Elevators Escalators Type Type Shibuya- Asakusa- Bound Bound Trains Trains Box-type, two Irregular underground divided 113.5m 100.8m 10.0m 3 2 floors Passenger movement trends and projection Figure 6 shows passenger movement trends from past years and a projection of the future. The number of passengers embarking and disembarking at Shimbashi Station has increased significantly in recent years due to redevelopment of areas around the station, disrupting passenger flow and becoming a major problem. Further impact to the number of passengers using Shimbashi Station is expected from the completion of the JR Ueno-Tokyo Line and from completion of railway networks of other railway operators. CHALLENGES FOR DRAFTING AN IMPROVEMENT PLAN This section outlines obstacles to the flow of passengers that transfer from the Ginza Line to other modes of transportation at Shimbashi Station, and obstacles to passenger flow created by the current station layout. This section also touches on the challenges of dealing with adjacent structures and preserving their status as civil engineering heritages. Current passenger flow Passenger flow simulations were performed to gain an understanding of passenger congestion, safety and other factors at Shimbashi Station in its current state. In reproducing current passenger flow, simulations accounted for passenger characteristics based on field surveys. Figures 7 and 8 show simulation results for the B1 floor concourse and B2 platform, respectively. Note that the service levels indicated on the legend of each diagram are based on the Manual for Transportation Plans Involving Large-Scale Development Areas.2 Figure 7 shows the heaviest concentration of passenger flow on the B1 floor concourse around the JR Exit Ticket Gate, and that there is significant passenger congestion on the concourse within the station and on stairways. Shimbashi Station has two ticket gates, the JR Exit Ticket Gate and the Tamuracho Exit Ticket Gate, but the figure shows that a vast majority of passengers move toward the JR Exit Ticket Gate while relatively few move toward the Tamuracho Exit Ticket Gate on the Shibuya side of the station. Passengers take relatively similar paths on the concourse, and there is a huge difference between the flow volumes where passengers can walk freely and where there is congestion. Figure 8 shows that many passengers board and exit Cars 1 and 2 of Shibuya- bound trains on the B2 floor platform, crowding around the edge of the platform and at the bottom of stairways around the JR Exit Ticket Gate and causing congestion on the platform and stairways. The figure shows that many passengers move toward the JR Exit Ticket Gate, and few move toward the Tamuracho Exit Ticket Gate off the edge of the Shibuya side of the platform. Figure 8 also shows continuous congestion between and beside the stairways on the Asakusa side of the platform for Shibuya-bound trains. This is because the pathways beside the stairways are narrow; as Picture 2 illustrates, the distance between passing trains and passengers walking on the platform is short. The current width of the pathways also does not allow enough space to install platform screen doors in the future as the stairways would be too close to the doors. Finally, Figure 8 shows that the B2 floor platform for Asakusa-bound trains allows for better flow than the platform for Shibuya-bound trains. These figures demonstrate the need for measures to mitigate the concentration of passengers moving toward the JR Exit Ticket Gate on the B1 floor concourse, and to disperse continuous congestion and mitigate congestion between and beside stairways on the Asakusa side of the B2 floor platform for Shibuya-bound trains. Impact on adjacent properties As shown in Figure 3, the JR Yamanote, Keihin Tohoku, and Tokaido Main Lines and Tokaido Shinkansen cross directly above the Ginza Line. Picture 3 shows the situation above ground, and Figure 9 is a longitudinal diagram of the intersection with the JR lines. Figure 9 shows that the floor slabs atop the B1 floor structures of the Ginza Line support the foundations of the supports for the JR Line Futababashi Elevated Bridge (“the JR Line Bridge”). Since the Shimbashi Station improvement work is part of excavation beneath these floor slabs, plans for the improvement work must take into account impact on the JR Line Bridge. Preserving historical value of civil engineering heritages As mentioned earlier, Shimbashi Station has been designated a JSCE Civil Engineering Heritage, and work plans for this large-scale improvement project must not damage the historical value of the station.