(Quoted from the website of the Bureau of Urban Development, Tokyo Metropolitan Government)
The Tokyo Metropolitan Government and the Tokyo Expressway Company Limited, the road administrator, are now planning to revitalize the abandoned Tokyo Expressway (commonly known as the KK Line), an elevated automobile-only road that runs above Ginza in central Tokyo, as the Roof Park Project (Tokyo Sky Corridor), an aerial corridor for pedestrians. The Tokyo Metropolitan Government and Tokyo Expressway Company, the road administrator, have formulated a policy to convert the KK Line into a pedestrian-oriented public space, as its role as an expressway has diminished with the construction of the new Metropolitan Expressway Inner Circular Route. This concept is said to be aimed at creating new values and attractions in Tokyo by shifting the space in the city center from being a car-first space to a people-centered space. In fact, the Tokyo Metropolitan Government announced its basic policy in March 2021, and in December 2023, the urban plan was changed to remove the KK Line from the designation as a "road" and position it as a public space such as a plaza, and preparations have been made in stages.
The KK Line, which will be transformed into the Roof Park Project (Tokyo Sky Corridor), is an elevated roadway that runs from Hibiya and Yurakucho to Ginza, Shimbashi, and Kyobashi near the boundary of Chiyoda, Chuo, and Minato wards, and its structure is very unique. The road, which opened in 1959, is operated by a private company (Tokyo Expressway Co., Ltd.), and is known for the fact that it was toll-free for a short period of time, with maintenance costs covered by revenues from tenants under the elevated railway tracks. The road itself consists of the rooftops of 14 reinforced concrete buildings (two stories above ground and one below) and 13 bridges connecting them, with a total length of approximately 2 km. The elevated structure is located about 2 stories above the ground (about 8 meters) and has the potential to connect the surrounding area in a single continuous line while overlooking the Ginza district. The road width (width of the elevated structure) is approximately 16 meters or more in some places, and after the renovation to the corridor, the plan is to take advantage of this width to create a plaza and terrace space in addition to pedestrian pathways.
The "Roof Park Project (Tokyo Sky Corridor)" will feature lush greenery, artwork, and other landscaping elements, as well as a "viewpoint" near major intersections that will offer panoramic views of the surrounding city. The plan is to make the aerial corridor itself a tourist attraction that attracts attention from around the world by displaying and staging exhibits that showcase the diverse personalities of the different areas along the corridor, such as Yurakucho, Ginza, and Shinbashi, as well as the unique culture of Japan. In the future, the project plans to introduce next-generation mobility vehicles, such as self-driving carts, to assist visitors in moving around and touring the corridor. It is expected to transform the conventional hard infrastructure of roadways into a soft space like a "hanging garden" where people can relax and walk, creating a new liveliness in the heart of the city.
The project is being promoted as a public-private partnership led by Tokyo Expressway Company Limited, which has managed the expressway, and the Tokyo Metropolitan Government. On April 4, the Tokyo Metropolitan Government and Tokyo Expressway Company announced the "Utilization Policy for the Revitalization of the Tokyo Expressway (KK Line)," and on April 18, a "KK Line Reborn Ceremony" was held on the elevated tracks, inviting all concerned. At this ceremony, the project name " Roof Park Project " and the concept " A Future Slowly Created by Everyone " were announced. The project name, "Roof Park Project," and the concept, "A Future Slowly Created by Everyone," were announced at the ceremony, indicating that the government, private sector, and local residents will work together to "slowly (steadily)" and "together" create a spacious town utilizing the rooftops of the urban infrastructure. In addition, in order to incorporate the opinions of various experts and local residents from the planning and development stages of the project, a "co-creation platform" has been established for participatory discussions. This is aimed at open project management that is not conventionally led by the government, and ideas for the creation of new public spaces are being solicited from a wide range of people.
The long-term plan is to begin construction in the mid-2020s, with the goal of completing the entire section in the 2030s or 2040s. However, the plan also calls for phased development, with some sections to be opened up gradually so that citizens can use this space as soon as possible. For example, in the Kyobashi 3-chome East Urban Area Redevelopment Project (scheduled for completion in 2030), located on the east side of the Ginza area, a new mixed-use building with a hotel and commercial facilities in the low-rise area is being planned, directly connected to the former KK Line. There is a possibility that the Roof Park Project (Tokyo Sky Corridor) will open from this section in conjunction with the completion of the redevelopment project. Until construction begins, it is expected that demonstration tests and events will continue to be held using the elevated facilities, and that studies will be conducted with a view to utilizing the facilities after the opening. In fact, the " Ginza Skywalk (Ginska), " an experience event that opens the highway to the public during Golden Week, will be held in 2023 and 2024, with guided tours along the 2-km elevated highway and café talk sessions in a grassed rest area. Even before the construction, efforts have been made to let citizens experience a "walk in the air of the future," and Tokyo Governor Yuriko Koike expressed her expectations for the project, saying at an event, "This will be a new space where people can enjoy walking in the middle of the city. She also expressed her expectations for the project.
The creation of a new pedestrian network that directly connects the major areas of central Tokyo, such as Ginza, Yurakucho, and Shinbashi, is expected to have a significant ripple effect on the surrounding areas. The opening of the Aerial Corridor is expected to dramatically increase circulation between previously separated areas and strengthen the circulation lines throughout the city, allowing tourists to move between multiple areas on foot or to walk from Shimbashi to Yurakucho. Governor Koike has stated, "I want to make the KK line (Roof Park Project (Tokyo Sky Corridor)) a tourist attraction that attracts attention from around the world, so that when people come to Tokyo, they first think of visiting the KK line. The extraordinary space of a lush green promenade stretching into the sky is expected to further enhance the brand value of Ginza, as well as have a ripple effect on commercial facilities along the street and increase the value of real estate in the surrounding area. The Roof Park Project (Tokyo Sky Corridor) is similarly expected to become an aerial park where visitors can enjoy the city center scenery after its completion, both in Japan and abroad. The Roof Park Project (Tokyo Sky Corridor) is expected to attract both domestic and international tourists to the city as an aerial park where they can enjoy the city's scenic beauty, and to help the local economy.
However, consideration of the surrounding environment is also essential to the realization of the project. Since the elevated structure is located in a valley between buildings, there are concerns that the noise (talking voices and sound from events) and reflected light from the large number of pedestrians visiting the area will affect adjacent commercial and residential facilities. Therefore, it is necessary to create a comfortable space in harmony with the surrounding area by devising sound and vibration insulation measures and landscaping. The project sponsor emphasizes that it will "carefully develop the community at the speed of human footsteps" (the meaning behind the concept of "slow construction") and aims to create a sustainable public space by taking the time to resolve issues.
The "Roof Park Project (Tokyo Sky Corridor)," which will be located in the middle of central Tokyo, is currently in the conceptual stage, but preparations are steadily underway, and when it fully opens in the 2030s or later, it may become a new landmark symbolizing Tokyo, as an aerial walkway where visitors can stroll while overlooking the Ginza district. It may become a new landmark symbolic of Tokyo. This is the first urban road infrastructure rehabilitation project of its kind in Japan, and its progress is likely to attract widespread attention in the years to come.