The route is a circumferential highway running through the outer wards of Tokyo.

It is a ring that lies approximately 8 km (5.0 mi) from the center of the city and goes through the wards of Edogawa, Katsushika, Adachi, Kita, Itabashi, Toshima, Shinjuku, Nakano, Shibuya, Meguro, and Shinagawa.

[2] 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 40 km/h (24.9 mph), and multiplying the affected distance by the affected time) was approximately halved from the previous week.

[3] The C2 begins and ends at the Bayshore Route, which serves to close the southeastern part of the loop.

Given the extensive tunneling and engineering challenges involved, construction costs for the route were estimated to be 2 trillion yen.