The track gauge difference is only 85mm in numbers,

The standard gauge used by South and North Korea and the broad gauge used by Russia have different widths. Because of this difference, train wheel axles (bogies) cannot simply cross the border.

Standard gauge (South Korea/North Korea) 1,435mm

Broad gauge (Russia) 1,520mm

        Two ways to resolve this difference at the border — ① Replacing the entire bogie (used at Khasan Station, Tumangang Station, etc.) ② Variable gauge technology that automatically adjusts wheel width as the train passes (commercialized in Spanish high-speed rail, etc.)
      

Bogie exchange method Variable gauge technology Already proven technology