This audio is generated by AI, so pronunciation and expressions may not be fully accurate. The narration is only in English.
Spanning about two kilometers, the full length of the KK Line was officially opened in 1966 as a dedicated roadway for vehicles. What set it apart, however, was that it was privately built and operated—yet completely toll-free. How was that possible?
"It was because the space under the road was leased out, with the income from that used to cover the construction and maintenance costs," explains Hanaki Mariko, Executive Managing Director and Head of the Project Promotion Office at Tokyo Expressway Co., Ltd., the company that built and operates the KK Line.
"The KK Line was a trailblazer in infrastructure development through private-sector initiative—a groundbreaking business model now known as PFI, or 'private finance initiative.' In fact, the nickname 'KK Line' came from how companies in Japan used to be labeled 'K.K. (Kabushiki Kaisha)' instead of 'Co., Ltd.' as they are now. The name was coined to differentiate our expressway from the Metropolitan Expressway, which it connects to."
Today, the rental space beneath the expressway is still home to about 380 restaurants, shops, and offices, with rental income continuing to sustain this public infrastructure without the need for tolls.
The KK Line, built over a filled-in moat and river once used for boat transport during the Edo period (1603-1868), was created to support the rapidly growing postwar car culture in Japan. Decades later, with plans to move the Nihonbashi section of the Metropolitan Expressway underground, the KK Line has been decommissioned—clearing the way for a new chapter of its existence.
"The KK Line will be transformed from a space for cars into a public space for people. We've named this project the Roof Park Project. Its most distinctive feature is that, instead of demolishing the existing roadway, we're revitalizing it to provide new value."
Rather than leaving the work to a single expert, the project brings together architects, creators, and specialists from a wide range of fields, encouraging them to think beyond their disciplines and discuss ideas collaboratively.
"Through this co-creation platform, we are making the planning process open and transparent. We also want to create opportunities for a broad range of people to participate in the project—not just local residents, but anyone interested in it."
In New York, the High Line—a former elevated railway transformed into an aerial greenway—draws large numbers of tourists. Hanaki points out, however, that the major thing that sets the KK Line apart from the High Line is its continuity with the past.
"The High Line created a new sense of liveliness by transforming the area, which had lost its vibrancy after the decommissioning of the railway line, into a public space. By contrast, the Roof Park Project is establishing a public space in areas like Kyobashi, Ginza, and Shinbashi, in the heart of central Tokyo, that have thrived with their own history and vitality since all the way back to the Edo period. The goal is to work with the surrounding neighborhoods to create new value and appeal, and to carry that energy into the future. We want to make the most of the character and potential that this place holds."
The potential of the KK Line has already been demonstrated in a past event.
"Those who participated in the walking event told us they had never seen views like this before. The city that they thought they knew looked completely different when seen from this height. Many of them were also thrilled to see the Shinkansen (bullet train) passing by at such close range. The views from the KK Line are full of gems, from Hibiya Park to the Sukiyabashi intersection and even the National Diet Building. I think the Deaflympics marathon runners will also enjoy the scenery as they race through."
The full redevelopment of the section is scheduled for completion between the 2030s and 2040s, though efforts are underway to open some sections earlier. Rather than prioritizing speed or efficiency, the project places importance on careful progress through dialogue with a wide range of people.
Located in the heart of Tokyo, the KK Line will be reborn as a lush, open space filled with all kinds of possibilities, from art to sports—where every visit brings new discoveries. The hope is that this project will help create new value and appeal in Tokyo as a city.
