A light rail line is a transportation option that combines features of street cars, trains, and subway or metro systems. They are often used in urban areas to complement replace existing public transportation facilities like buses, trams, or subways. A light rail line may run on existing train tracks or along specially-built rails on city streets to carry passengers from home to work or leisure activities.
The term light rail comes from the German term Stadtbahn, which translates literally to mean "city rail" in English. Contrary to popular belief, a light rail line is not distinguished from heavy rail systems by its lighter weight. In fact, light rail systems often weigh as much or more than regular trains, and can cost just as much to build. Instead light rail transit is characterized as a fast moving system capable of moving smaller loads than heavy rails. Heavy rail systems, on the other hand, usually include vehicles like freight trains, regional and national passenger trains, and subways.
There are several different types of light rail service designed to meet the needs and infrastructures of different cities. In areas with extensive existing track networks, the tracks are often adapted for use with light rail trains. In many cities, these tracks are poorly located or non-existent, so special tracks must be built along the proposed route. The trains used in a light rail line can be driven by human-operators or automatic operating systems, though human drivers are often used to help minimize accidents where the train runs along a roadway.
These trains are usually powered by overhead electric lines, which are out of reach of pedestrians and help avoid the need for dangerous third-rail systems. It is possible to use a third rail that is only electrified when the train is directly on top, which prevents injury and electrical shock to pedestrians. In some cities, the light rail line is powered by diesel fuel, which may be more energy-efficient than electrical power depending on the type of system in use.
Passengers may purchase tickets or passes for these trains using different methods depending on the city. In some areas, machines at each light rail stop are used to automatically dispense tickets. As the passenger boards the train, he or she may insert the ticket into a turnstile, or hold the ticket to submit to train staff upon request. Many modern light rails are based on an honor-system, where random ticket inspections are performed to help maximize compliance. Those who fail to purchase tickets may be removed from the train at the next stop, or be subject to tickets or fines.