Comment by m4rtink

There are some lines that were originally built as regular narrow gauge railways and later converted to standard gauge supporting Shinkansen trainsets.

This is called Mini-Shinkansen: https://en.wikipedia.org/wiki/Mini-Shinkansen

This comes with limitations, as the maximum track speed on these converted lines is apparently around 130 km/h.

None of the actual Shinkansen stadard lines have level crossings.