Ōhashi Junction
The Ōhashi Junction is a covered one-quadrant Interchange of the Shuto Expressway system in Tokyo. It connects the Shibuya Route and the Central Circular Route. It was in construction from 2003 to 2013. It was partially opened in 2010 and fully completed in 2015. The completed interchange links the Central Circular Route (Shuto Expressway) through the Yamate Tunnel as far as the Bayshore Route in Shinagawa. The cost of the project was $90 billion yen.
It is designed to be as compact as possible and environmentally friendly. The Shibuya Route is an elevated highway and the Central Circular Route is underground; the Ohashi junction is a spiral bridge with four loops to allow cars to go between the two. The junction rises to a height of 35m above ground, 36m underground and has a diameter of between 130 and 175 meters.
The Meguro Sky Garden is a 7000 m2 linear roof garden park in Ōhashi, Meguro, Tokyo, Japan, constructed over the Ohashi junction rising from 15 to 35 meters above street level. The garden serves as a freeway lid.
The road junction redevelopment also includes high rise residential housing, retail, a local Meguro government branch office, a library, community meeting rooms and all-weather sports facilities.
History
Until 1969, a depot on the former Tokyu Tamagawa tramway was located at the site. Note this tramway is different from the existing Tōkyū Tamagawa Line.The day after the Tamagawa Tramway line was discontinued the Ohashi Bus Depot operated on the site for 33 years until its closure in September 2002.
The initial planning decision for the junction was made August 13th 1990.
The Central Circular Route's Yamate Tunnel reached Ōhashi Junction when the section between Nishi-Shinjuku and Ōhashi opened on 28 March 2010, bringing the new stacked-loop junction into service. The Meguro Sky Garden opened on 30 March 2013 on the roof of the junction's loop.
On 7 March 2015 the Central Circular Shinagawa Line opened, completing the Central Circular Route and providing continuous travel via the Yamate Tunnel to the Bayshore Route.
Design and environmental measures
The project was planned and branded as the Ohashi "Green" Junction, integrating the expressway works with local redevelopment and public open space. Its concept emphasized "three greens": a roof park around the 400 m loop; greened townscape on the exterior walls using creeping fig; and a nature‑regeneration area on the roof of the ventilation station.Inside the loop a 3,000 m2 multi‑purpose lawn, Opus Yume Hiroba, was created for community use.
The junction's stacked elliptical ramps connect the elevated Shibuya Route and the underground Central Circular Route across a height difference of about 70 m, with a loop length of about 400 m; the enclosing structure reduces noise and emissions impacts on the surrounding neighborhood.
The outer walls of Ōhashi Junction are almost the same size as the Colosseum. The outer wall design was inspired by the Colosseum, with decorative false windows and slits on its walls added to reduce the sense of oppression on the surrounding area.
Impacts
Construction of the junction reduced the distance needed for motorists to travel between the two roads.Construction forced residents to relocate from the junction site. The development was undertaken as a n integrated development combining junction construction with a redevelopment project implemented by the Tokyo Metropolitan Government. The original residents are said to be living in these new buildings.
Approximately 38,000 square metres of land was redeveloped for the junction and two high rise buildings. The Meguro Ward Park built on the rooftop covers an area of approximately 7,000 square metres.
Analysis of data before and after the opening of the junction showed a decrease in nearby traffic speeds. Average traffic speeds at Ikejiri Entrance to Ohashi Junction dropped from 66.53km/h in 2006 to 36.84km/h in 2010, with a larger variance. The analysis concluded that decrease in speed due to traffic convergence cannot be ignored as a contributing factor to congestion on Metropolitan Expressway Route No. 3.
Commentary accompanying the Japan Society of Civil Engineers prize described the sight of the four tube-like connecting viaducts and the Metropolitan Expressway Route 3 Shibuya Line elevated highway, interwoven with the main structure, as violent.
Awards and recognition
The junction and rooftop park have received multiple national awards, including:- 2013 Good Design Award "Future Creation Design Award" for Ōhashi Junction.
- 2014 Japan Society of Civil Engineers Environment Prize for the completion of the Ohashi "Green" Junction.
- 2015 JSCE Design Prize for Ōhashi Junction.
- 2014 Urban Green Technology Contest for Meguro Sky Garden.
- 2015 JSCE Outstanding Civil Engineering Achievement Award for the Ohashi Ramp Tunnel works using an advanced tunnel enlargement method to join large shield tunnels without surface excavation.