Distance between a pair of rails measured between the inside edges of the rail heads.
The following track gauges are in use: Standard gauge: 1.435 m
Large gauge: 1.524 m (VR, SZR) 1.600 m (CIE, NIR)
1.668 m (RENFE, CP)
Narrow gauge: 0.60 m, 0.70 m, 0.75 m, 0.76 m, 0.785 m, 0.90 m, 1.00 m.