Japan's unique situation is probably the only thing that makes the Chuo Shinkansen pencil out.
- Unlike most rail networks, the Japanese conventional rail network is narrow gauge while the Shinkansen is standard gauge, eliminating any chance of network effects from speeding up conventional trains on the high speed network as well.
- The Chuo route is extremely mountainous, so most of the route is in tunnels, and in tunnels there isn't really an increase in land acquisition costs as you increase curve radii for higher speeds.
- Unlike most rail networks, the Japanese conventional rail network is narrow gauge while the Shinkansen is standard gauge, eliminating any chance of network effects from speeding up conventional trains on the high speed network as well.
- The Chuo route is extremely mountainous, so most of the route is in tunnels, and in tunnels there isn't really an increase in land acquisition costs as you increase curve radii for higher speeds.