From PlanningWiki
A train is a vehicle, or group of connected vehicles, that runs on rails. It is a modular vehicle: it consists of modules, called "cars" or "rolling stock", which are used to carry people and freight. Because railroads are typically separate from roads, and rails are more expensive than merely paving new roads, and trains are capable of carrying higher numbers of people per vehicle than buses, trains tend to be used in metropolitan areas with strong downtowns, high-population-density areas, and other locations with heavy ridership characteristics (such as the Disney World monorail, which connects the entrance gate with hotels and theme parks).
