The Central Circular Route has a total length of . It is a ring that lies approximately from the center of the city and goes through the wards of
Edogawa,
Katsushika,
Adachi,
Kita,
Itabashi,
Toshima,
Shinjuku,
Nakano,
Shibuya,
Meguro, and
Shinagawa. The eastern half is an elevated structure and the western half is an underground one. The
Yamate Tunnel is a deep tunnel constructed beneath Yamate Street, the first section over in length, was opened to traffic on 22 December 2007. From 2010, the tunnel extended the Central Circular Route south from near
Ikebukuro to
Ohashi Junction connecting with
Route 3. The last through
Meguro and
Shinagawa was opened to traffic on 7 March 2015. When this last section of the tunnel opened the Yamate Tunnel formed Japan's longest, and the world's second longest road tunnel. During the tunnel's first week of operations, traffic volume on the
Inner Circular Route was reduced by seven percent from the previous week, and congestion on expressways inside the Central Circular Route (an index measured by recording segments where average traffic speed is less than , and multiplying the affected distance by the affected time) was approximately halved from the previous week. The C2 begins and ends at the
Bayshore Route, which serves to close the southeastern part of the loop. ==History==