Generally, a Japanese Shinkansen (bullet train) cannot run on normal tracks because they use different "gauges" (the width between the rails). Standard Shinkansen tracks use Standard Gauge (1,435 mm), while most of Japan's conventional "normal" tracks use Narrow Gauge (1,067 mm). This physical difference makes "through-running" between the two systems impossible for standard trains. However, there are two notable exceptions: the "Mini-Shinkansen" routes (the Akita and Yamagata lines) use conventional tracks that were specifically "re-gauged" to the wider standard gauge to allow bullet trains to reach those cities. Additionally, Japan has experimented with "Gauge Change Trains" (Free Gauge Trains) that can adjust their wheels while moving, though these have not yet seen widespread commercial use due to weight and cost issues. In most other countries like France (TGV) or Germany (ICE), high-speed trains can run on normal tracks because their entire national networks use the same standard gauge.