The Shinkansen route broadly follows the alignment of the conventional
Tōkaidō Main Line, which in turn traces the course of the historic
Tōkaidō highway. For centuries, the Tōkaidō was one of Japan’s most important transport corridors, linking the political and cultural centers of the
Kansai region (including Kyoto and Osaka) with the
Kantō region (Tokyo) via the
Tōkai region (Nagoya). The name "Tōkaidō" literally means "eastern sea road", referring to the route running along the Pacific coast of central Honshū. The
Tōkaidō Main Line, completed in stages beginning in the late nineteenth century, was one of Japan’s earliest trunk railways and largely followed the alignment of the ancient highway. At the end of the 1930s, the government conceived a along the Tōkaidō corridor continuing to
Shimonoseki at the southwestern tip of Honshū. The line was intended to cover the nearly distance in about nine hours and to form the first stage of an East Asian rail network serving
Japan's overseas territories. The onset of
World War II halted the plan in its early stages, although three tunnels bored for this project were later incorporated into the Shinkansen route. By 1955, the Tōkaidō Main Line between Tokyo and Osaka was severely congested. Even after electrification the following year, it remained the busiest line in Japan’s railway network, with demand roughly double its capacity. In 1957, a public forum examined "The Possibility of a Three-hour Rail Trip Between Tokyo and Osaka." The opening was timed to coincide with the
1964 Summer Olympics in Tokyo. When service began, two train types operated: the express
Hikari, which covered the Tokyo–Osaka route in four hours, and the all-stops
Kodama, which required five hours. A test run on 25 August 1964 simulating a
Hikari service was broadcast nationwide by
NHK. Higher speeds were permitted primarily to recover from delays. In November 1965, timetables were revised to reduce travel times to for
Hikari services and for
Kodama services, with operation allowed under normal conditions. Despite these challenges, the World Bank loan taken out in 1959 was fully repaid in 1981. Following the 1987 privatization of JNR, the new operator,
JR Central, launched a program to raise operating speeds through infrastructure upgrades and new rolling stock. This effort produced the
300 series and the introduction of the super-express
Nozomi service on 14 March 1992, reducing travel time to two and a half hours and permitting speeds from to . Shinkansen platforms at Tokyo's
Shinagawa Station opened in October 2003 to reduce congestion at the Tokyo terminal, accompanied by a major timetable revision that expanded the number of
Nozomi services, surpassing the number of
Hikari services. A planned station at
Rittō—between Maibara and Kyoto—was canceled in 2007 after political opposition and a
Supreme Court of Japan ruling invalidated the city’s construction bond. A subsequent speed increase, to the current maximum, was announced in 2014 and introduced on 14 March 2015 following the adoption of improved braking technology on the
N700 series. == Stations and service patterns ==