Tokaido (also labeled the Taiheiyo Belt) represents a considerable accumulation of infrastructures and productive forces along the Tokyo-Osaka corridor, which is its core. The term refers to the imperial road that linked Edo (Tokyo) to Kyoto but now refers to an urban region accounting for more than 83 million people; 70% of the Japanese population. The most important agglomerations are the extended metropolitan region of Tokyo with a population of 35 million, Nagoya and Osaka with a respective population of 8 and 17 million. There are also several cities of over 1 million inhabitants (Kobe, Kyoto, and Yokohama). The corridor is strongly influenced by geographical constraints with a mountainous inland Japan and three major coastal plains around bays (Bays of Tokyo, Nagoya, and Osaka).
The cohesion of the corridor is assumed by massive transport infrastructures including ports, airports, highways, and especially a high-speed train network (Shinkansen). The first rail connection in the corridor was built in the 1880s. In 1930, an express train on the Tokaido Line took an average of eight hours and 20 minutes between Tokyo and Osaka. The high-speed train system reduced that time to 4 hours by the 1960s and new generations of trains further reduced this trip to two hours thirty minutes by 2000.