Some other lines in Japan use 1,372 mm (4' 6”) or 762 mm (30”) gauge. But the majority, over 83% in terms of distance, of Japan's railways are built to Cape Gauge, 1,067 mm (3' 6”). The name comes from its adoption in 1873 by the Cape Colony (later part of the Union of South Africa).

Japan primarily utilizes two different track gauges for its extensive railway network: 1,067 mm (3 ft 6 in), known as "Cape Gauge" or narrow gauge, and 1,435 mm (4 ft 8.5 in), which is the international "Standard Gauge." Roughly 80% of Japan's rail lines, including the majority of the conventional JR lines and private railways, use the 1,067 mm narrow gauge. This choice dates back to the 19th century when British engineers influenced the initial construction. In contrast, the world-famous Shinkansen (bullet train) network exclusively uses the 1,435 mm standard gauge. This wider base provides significantly more stability, which is essential for the extreme high speeds—often exceeding 300 km/h—that these trains maintain. There are also a few "Mini-Shinkansen" lines and private subways that use standard gauge, as well as a rare 1,372 mm "Scotch Gauge" used by the Keio Corporation and some Tokyo trams.