>The difference in gauge is very small (3.5”) when the average railhead width is just over 2.5” leaving only one inch which is too narrow for most wheel flanges

>The difference in gauge is very small (3.5”) when the average railhead width is just over 2.5” leaving only one inch which is too narrow for most wheel flanges. In this situation four rails are used: https://commons.wikimedia.org/wiki/File:Rail_Baltica_Lietuva.jpg https://commons.wikimedia.org/wiki/File:Rail_Baltica_Lietuva...