There are several options nowadays. For instance, the Spanish train maker Talgo holds many patents for variable-gauge railroad wheel systems. Such systems can b

There are several options nowadays. For instance, the Spanish train maker Talgo holds many patents for variable-gauge railroad wheel systems. Such systems can be used at scale for large projects. https://en.m.wikipedia.org/wiki/Variable_gauge https://en.m.wikipedia.org/wiki/Variable_gauge