Railroads become available in the Modern Age. The specific technology or civic required to unlock them was not provided in the original text. [This information should be added when available]
Roads within a settlement automatically upgrade to railroads when a Rail Station is built. Constructing multiple Rail Stations across your empire will connect settlements and create a functional rail network.
Once two or more Rail Stations exist on the same continent, units can fast travel between them. To use a Rail Station:
The unit will instantly teleport to the chosen station.