Preparation of Articles for the Symposium Report

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.

Measures against age-related deterioration As mentioned in the introduction, the Ginza Line is the oldest subway line in Japan, and like other underground structures, it has suffered cracks, water leakage and other forms of age-related deterioration. In response,

Tokyo Metro established a maintenance committee that included outside experts, and from 2004 to 2005 the committee surveyed Ginza Line tunnels between Asakusa and Suehirocho Stations (the oldest stretch of the line) and assigned health grades to them. The surveys revealed that subway structures are performing sufficiently, and that reinforcement work to restore and improve their strength and load bearing ability is not necessary at this time.

SHIMBASHI STATION IMPROVEMENT PLAN

In the course of drafting an improvement plan to mitigate congestion on platforms, ensure passenger safety, and to facilitate transfers to other modes of transportation, the results of the passenger flow simulations described above in “Challenges for Drafting an Improvement Plan” were used to propose the replacement of stairways and vertical transportation facilities on the B1 floor concourse and B2 floor platform for Shibuya-bound trains, as well as sweeping changes to the station layout. Note that this plan calls for the improvement of the platform for Shibuya-bound trains only; the platform for Asakusa-bound trains is not as congested and will remain in its current state. Below are specific details about the plan.

Layout Figures 10 and 11 are overviews of improvement plans for the B1 floor concourse and B2 floor platforms, respectively, and Figure 12 is a three-dimensional diagram of the station after improvements. First, the Tamuracho Exit Ticket Gate on the B1 floor concourse will be relocated as shown in Figures 10 and 12. The ticket gate currently faces Exits 7 and 8, but will be reoriented to face Exit 6, the main stairway passengers use to transfer to JR lines, in an effort to make the flow of passengers transferring to JR and other lines smoother. As shown in Figures 11 and 12, the Shibuya side of the B2 floor platform for Shibuya-bound trains will be extended 26.5 meters and the train stop point will be moved 37 meters. The extension will redirect passenger flow on the Shibuya side of the platform away from the stairway to the JR Exit Ticket Gate on the Asakusa side and toward the Tamuracho Exit Ticket Gate on the Shibuya side. The new stairway from the extended part of the platform will add a direct route up to the Tamuracho Exit Ticket Gate and will increase passenger traffic to that ticket gate. In addition, the stairway furthest away on the Asakusa side of the B2 floor platform for Shibuya-bound trains will be demolished, and an elevator facing the opposite direction will be installed in its place. Doing so will allow passengers exiting Cars 5 and 6 at the new train stop point to proceed smoothly from the B2 floor platform to the B1 floor concourse. Finally, the decorative stairway wall on the narrow pathway between the stairs and the edge of the platform for Shibuya-bound trains will be demolished to create more room for passing passengers. Changes to the layout of the B1 floor concourse, the extension of the B2 floor platform for Shibuya-bound trains and the addition and relocation of stairways and

vertical transportation facilities on that platform are planned in an effort to streamline passenger flow. Table 2 shows the change to the number of stairways and vertical transportation facilities planned for the platform for Shibuya-bound trains.

Table 2 Current and Planned Vertical Transportation System Current Planned Number Number Escalators 2 3 Elevators 3 3

Verification with passenger flow simulations Figures 13 and 14 show the results of passenger flow simulations on the B1 floor concourse and B2 floor platforms, respectively, at Shimbashi Station after improvements. Note that these results account for the effects of the future completion of the JR Ueno-Tokyo Line and other railway networks planned by other railway operators on passenger flow at Shimbashi Station. Figure 13 shows that the replacement of stairways and vertical transportation facilities, and changes to the station layout will redirect passengers away from the JR Exit Ticket Gate and toward the Tamuracho Exit Ticket Gate on the B1 floor concourse, and decrease flow concentration around the JR Exit Ticket Gate. Figure 14 confirms that extending the B2 floor platform for Shibuya-bound trains, thus changing the train stop point, and replacing stairways and vertical transportation facilities will disperse passengers throughout the entire platform, mitigating congestion by decreasing flow concentration beside stairways and at both the Shibuya and Asakusa ends of the platform. This improvement plan strives to streamline transfers from the B1 floor concourse to other modes of transportation as well as to mitigate congestion and ensure passenger safety on the B2 floor platform for Shibuya-bound trains. The plan has been deemed capable of improving the functionality of Shimbashi Station.

GINZA LINE SHIMBASHI STATION WORK PLAN

Work plans were drafted with concern given to satisfying the conditions that the operating line operates normally, that current passenger flows are ensured, and that improvements coexist with structures that have historical value as civil engineering heritages, as explained above in “Challenges for Drafting an Improvement Plan”. Below are specific details about the plan.

Work sequence Figures 15 and 16 are longitudinal diagrams of the platform for Shibuya-bound trains, and Table 3 explains the work sequence. In an effort to streamline passenger flow, consideration was given to avoid going below the current number of stairways and vertical transportation facilities during the process of installing stairways, escalators and elevators. Figures 17 and 18 are cross-sectional diagrams of the intersections of the Ginza and JR Lines. The process of removing the B1 floor concourse floor slabs and replacing supports after ground improvement in the course of widening the concourse and the B2 platforms will be repeated to excavate the earth beneath the Phantom Platform of Shimbashi Station.

Table 3 Work Sequence 1. Create opening for work 8. Demolish Asakusa-side stairway 2. Install gantry 3. Build B Stairway 9. Build elevator 4. Demolish stairway/escalator 10. Demolish escalator 5. Excavate inside station 11. Build escalator 6.Extend platform 12. Demolish central stairways 7. Build A Stairway Install signal transmission facility Demolish decorative stairway wall

Dealing with adjacent structures As mentioned earlier, the structure of Shimbashi Station is integrated with the JR Line Bridge supports, and there was concern that this improvement work would impact the bridge supports. FEM analysis was implemented to examine the impact of improvement work on the JR Line Bridge and on Ginza Line tracks. The results of the analysis showed that these impacts fall within construction control values for both horizontal and vertical displacement set forth by Tokyo Metro.

Consideration for civil engineering heritages This work plan calls for a 5.0-meter widening of the B1 floor concourse and the 26.5-meter extension of the Shibuya side of the B2 floor platform for Shibuya- bound trains. The improvement work will shorten the Phantom Platform of Shimbashi Station built by Tokyo Rapid Transit Railways, but will reveal to the public and increase awareness of what is now a little-recognized (Picture 4) civil engineering heritage (Figure 19).

CONCLUSION

This report is a proposal of one way to undertake large-scale improvement work on an important subway station that serves over 200,000 people each day. Planning large-scale improvement work on Shimbashi Station or any other civil engineering structures with historical value requires that the planners pay respect to great works of the past, and pass on technical traditions to the next generation of civil engineers. Among continuing challenges for railway operators are working to stay abreast of redevelopment and other minute changes to areas around stations and building systems to enable the drafting of plans to rapidly improve underground spaces and subway stations if necessary. As a final thought, it would be wonderful if this report could serve as a reference for the planning, design and execution of large-scale improvement work in narrow underground spaces in the future.

ACKNOWLEDGMENTS

We thank the people of Chikatetsu Hakubutsukan of Metro Cultural Foundation (Tokyo Subway Museum) for their help with literature and other information.

REFERENCES

Tokyo Underground Railway: The History of the Tokyo Underground (Last volume), 1934. Improvement Plan for Ginza Line Shimbashi Station, a JSCE Civil Engineering Heritage; Summary of JSCE Annual Academic Lectures, No. 6, Vol.70, p. 855-856. Taketoshi OGINO, Ryuji FUKUDA, Tsuyoshi KORIYAMA, Akihiro SATO, 2015.